c) Two copies of three different genomes
c) Two copies of three different genomes
c) 45 AB, 45 ab
c) 45 AB, 45 ab
c) 3 and 4
c) 3 and 4
b) Possibility of double cross over
b) Possibility of double cross over
b) 7:1:1:7
b) 7:1:1:7
c) SGHL
c) SGHL
b) A to G, C to T, C to G and T to A
b) A to G, C to T, C to G and T to A
a) 35 and 37
a) 35 and 37
a) missense mutation
a) missense mutation
c) A is correct. R is wrong explanation of A
c) A is correct. R is wrong explanation of A
c) 9 cM
c) 9 cM
i) The name of this phenomenon is known as Linkage.
This is reported in Sweet pea Lathyrus odoratus by Willium Bateson & Reginald C Punnet in 1906.
Genes for Purple colour and Long pollen grain were found close together in the same homologous pair of chromosomes – They do not assort independently and this condition is known as linkage.
i) The name of this phenomenon is known as Linkage.
This is reported in Sweet pea Lathyrus odoratus by Willium Bateson & Reginald C Punnet in 1906.
Genes for Purple colour and Long pollen grain were found close together in the same homologous pair of chromosomes – They do not assort independently and this condition is known as linkage.
i) It is three point test cross – It refers to analysing the inheritance, patterns of three alleles by crossing a triple recessive herterozygote with a triple recessive homozygote.
ii) The relative distance between the three alleles & the order in which they are located can be determined with the help of frequency of recombination between them.
All the loci are linked because all the RF values are considerable less then 50%. In AC loci show highest RF value, they must be farthest apart. There fore the B locus must lie between them. The order of genes should be abc. A genetic map can be drawn.
A final point note that two small map distances. 19.9 m.u and 21.75 m.u is add up to 41.95 m.u which is greater then 40.16 m.u the stance calculated for 1 and g. We must identify the two least number of progenius (totalling 8) in relation to recombination of AC. These two least progenius are double cross over. The two least progenies not only counted once should have count each of them twice because each represents a double recombinant progeny. Hence, We can correct the value adding the number 114 + 125 + 116 + 128 + 5 + 14 + 4 = 500 of the total 1200 this number exactly 41.65% which is identical with the same of two component values.
The test cross parental combination can be rewritten as follows.
Gene order showing double recombinant.
i) It is three point test cross – It refers to analysing the inheritance, patterns of three alleles by crossing a triple recessive herterozygote with a triple recessive homozygote.
ii) The relative distance between the three alleles & the order in which they are located can be determined with the help of frequency of recombination between them.
All the loci are linked because all the RF values are considerable less then 50%. In AC loci show highest RF value, they must be farthest apart. There fore the B locus must lie between them. The order of genes should be abc. A genetic map can be drawn.
A final point note that two small map distances. 19.9 m.u and 21.75 m.u is add up to 41.95 m.u which is greater then 40.16 m.u the stance calculated for 1 and g. We must identify the two least number of progenius (totalling 8) in relation to recombination of AC. These two least progenius are double cross over. The two least progenies not only counted once should have count each of them twice because each represents a double recombinant progeny. Hence, We can correct the value adding the number 114 + 125 + 116 + 128 + 5 + 14 + 4 = 500 of the total 1200 this number exactly 41.65% which is identical with the same of two component values.
The test cross parental combination can be rewritten as follows.
Gene order showing double recombinant.
Mis-sense Mutation:
The mutation where the codon for one amino acid is changed into a codon for another amino acid is called Missense or non-synonymous mutations.
Non-sense Mutation:
The mutations where the codon for one amino acid is changed into a termination or stop codon is called Nonsense mutation.
Mis-sense Mutation:
The mutation where the codon for one amino acid is changed into a codon for another amino acid is called Missense or non-synonymous mutations.
Non-sense Mutation:
The mutations where the codon for one amino acid is changed into a termination or stop codon is called Nonsense mutation.
- It is a change in the arrangement of gene loci,
- Here the duplicated segment is located immediately aftear the normal segment but the gene sepuence order will be reversed – (Paracentric inversion)
- It is a change in the arrangement of gene loci,
- Here the duplicated segment is located immediately aftear the normal segment but the gene sepuence order will be reversed – (Paracentric inversion)
Salient features of the chromosomal theory of inheritance:
* Somatic cells of organisms are derived from the zygote by repeated cell division (mitosis). These consist of two identical sets of chromosomes. One set is received from female parent (maternal) and the other from male parent (paternal). These two chromosomes constitute the homologous pair.
* Chromosomes retain their structural uniqueness and individuality throughout the life cycle of an organism.
* Each chromosome carries specific determiners or Mendelian factors which are now termed as genes.
* The behaviour of chromosomes during the gamete formation (meiosis) provides evidence to the fact that genes or factors are located on chromosomes.
Salient features of the chromosomal theory of inheritance:
* Somatic cells of organisms are derived from the zygote by repeated cell division (mitosis). These consist of two identical sets of chromosomes. One set is received from female parent (maternal) and the other from male parent (paternal). These two chromosomes constitute the homologous pair.
* Chromosomes retain their structural uniqueness and individuality throughout the life cycle of an organism.
* Each chromosome carries specific determiners or Mendelian factors which are now termed as genes.
* The behaviour of chromosomes during the gamete formation (meiosis) provides evidence to the fact that genes or factors are located on chromosomes.
Crossing Over – it is a very significant biological process
It is a precise one with several stages
i) Synapsis:
During zygotene – of prophase. I of meiosis I the homologous chromosomes come and align side by side known as – bivalents.
This pairing – is known as synapsis or syndesis.
Types of synapsis
ii) Tetrad Formation:
Each homologous chromosome of – a bivalent begin to form two identical sister chromatids – held together by a centromere.
Each bivalent has 4 chromatids – (tetrad stage),
iii) Cross Over:
At pachytene stage cross over occur. The points of contact at one or more points between non-sister chromatids is called Chiasmata.
Crossing over is exchange of corresponding segments occur, in the chiasma region.
Synaptonemal Complex (SC)
The highly organised structure of filaments called SC – facilitate chiasma formation.
SC formation & chiasma formation – is absent in Drosophila
Terminalisation:
After crossing over, chiasma starts to moving towards the terminal end of chromatids is known as terminalisation. Complete separation of homologous chromosomes occurs after terminalization.
Crossing Over – it is a very significant biological process
It is a precise one with several stages
i) Synapsis:
During zygotene – of prophase. I of meiosis I the homologous chromosomes come and align side by side known as – bivalents.
This pairing – is known as synapsis or syndesis.
Types of synapsis
ii) Tetrad Formation:
Each homologous chromosome of – a bivalent begin to form two identical sister chromatids – held together by a centromere.
Each bivalent has 4 chromatids – (tetrad stage),
iii) Cross Over:
At pachytene stage cross over occur. The points of contact at one or more points between non-sister chromatids is called Chiasmata.
Crossing over is exchange of corresponding segments occur, in the chiasma region.
Synaptonemal Complex (SC)
The highly organised structure of filaments called SC – facilitate chiasma formation.
SC formation & chiasma formation – is absent in Drosophila
Terminalisation:
After crossing over, chiasma starts to moving towards the terminal end of chromatids is known as terminalisation. Complete separation of homologous chromosomes occurs after terminalization.
Proposed by Robin Holliday in 1964
Steps:
* Homologous DNA molecules are paired side by side with their duplicated copies of DMAs
* One strand of both DNAs cut in one place by the enzyme endonuclease.
* The cut strands cross and join the homologous strands – Holliday junction.
* Holliday junction migrates away from the original site, a process called branch migration, as a result heteroduplex region is formed.
* DNA strands may cut along through the vertical (V) line or horizontal (H) line.
* The vertical cut will result in heteroduplexes with recombinants.
* The horizontal cut will result in heteroduplex with non recombinants.
Proposed by Robin Holliday in 1964
Steps:
* Homologous DNA molecules are paired side by side with their duplicated copies of DMAs
* One strand of both DNAs cut in one place by the enzyme endonuclease.
* The cut strands cross and join the homologous strands – Holliday junction.
* Holliday junction migrates away from the original site, a process called branch migration, as a result heteroduplex region is formed.
* DNA strands may cut along through the vertical (V) line or horizontal (H) line.
* The vertical cut will result in heteroduplexes with recombinants.
* The horizontal cut will result in heteroduplex with non recombinants.
In Nicotiana self sterility or self-incompatibility is due to multiple alleles.
The pollen from a plant is unable to germinate on its own stigma – and no fertilization.
The gene for self incompatibility can be – ‘S’ which has allelic series S 1, S 2, S 3, S 4 & S 5.
Cross-fertilizing tobacco – were not always homozygous as S 1 S 1 or S 2 S 2, but heterozygous
Crosses between different S 1 S 2 plants, pollen tube did not develop normally.
But effective – development observed when cross was made with other than S 1 S 2 Eg. S 3 S 4.
In Nicotiana self sterility or self-incompatibility is due to multiple alleles.
The pollen from a plant is unable to germinate on its own stigma – and no fertilization.
The gene for self incompatibility can be – ‘S’ which has allelic series S 1, S 2, S 3, S 4 & S 5.
Cross-fertilizing tobacco – were not always homozygous as S 1 S 1 or S 2 S 2, but heterozygous
Crosses between different S 1 S 2 plants, pollen tube did not develop normally.
But effective – development observed when cross was made with other than S 1 S 2 Eg. S 3 S 4.
Zeamays (maize) – monoecious plant
Made & Female flowers are present on the same plant.
* Terminal inflorescence – arise from tassel bear staminate flowers
* Lateral inflorescence – arise from ear or cob bear pistillate flowers.
* Unisexvality in maize – occurs through selective abortion of ear florets and pistils in tassel florets.
* The allele for barren plant (ba)- when homozygous makes the stalk staminate (eliminating silk and ears)
* The allele for tassel seed (ts) – transforms tassel into a pistillate structure (no pollen produced)
* Most of these mutations are shown to be defects in Gibberellins biosynthesis.
* Gibbercilins play an important role in the suppression of stamens in florets on the ears.
Zeamays (maize) – monoecious plant
Made & Female flowers are present on the same plant.
* Terminal inflorescence – arise from tassel bear staminate flowers
* Lateral inflorescence – arise from ear or cob bear pistillate flowers.
* Unisexvality in maize – occurs through selective abortion of ear florets and pistils in tassel florets.
* The allele for barren plant (ba)- when homozygous makes the stalk staminate (eliminating silk and ears)
* The allele for tassel seed (ts) – transforms tassel into a pistillate structure (no pollen produced)
* Most of these mutations are shown to be defects in Gibberellins biosynthesis.
* Gibbercilins play an important role in the suppression of stamens in florets on the ears.
The diagrammatic representation of the position of genes and related distances between the adjacent genes is called genetic mapping. It is directly proportional to the frequency of recombination between them. It is also called a linkage map.
Uses of genetic mapping:
* It is used to determine gene order, identify the locus of a gene and calculate the distances between genes.
* They are useful in predicting the results of dihybrid and trihybrid crosses.
* It allows the geneticists to understand the overall genetic complexity of the particular organism.
The diagrammatic representation of the position of genes and related distances between the adjacent genes is called genetic mapping. It is directly proportional to the frequency of recombination between them. It is also called a linkage map.
Uses of genetic mapping:
* It is used to determine gene order, identify the locus of a gene and calculate the distances between genes.
* They are useful in predicting the results of dihybrid and trihybrid crosses.
* It allows the geneticists to understand the overall genetic complexity of the particular organism.
* Tetraploidy: Crosses between diploid wheat and rye.
* Hexaploidy: Crosses between tetraploid wheat Triticum durum (macaroni wheat) and rye.
* Octoploidy: Crosses between hexaploid wheat T. aestivum (bread wheat) and rye. Hexaploidy Triticale hybrid plants
12th Bio Botany Guide Chromosomal Basis of Inheritance Additional Important Questions and Answers
I. Fill in the blanks
1. The scientists who independently rediscovered mendelian works were
De Vries, Correns & Tschermak
2. The worm-shaped cells formed during cell division are called in the earlier period as
Chromosomes
3. Who postulated that the chromosomes of a cell are responsible for transferring heredity
Wilhelm Roux (1883)
4. ……………………… was the first to find out physical mutagen in Drosophila
Muller (1927)
5. ………………………used X-rays for the first time to induce mutation in the fruit fly
H.J. Muller
6. Induced mutations are planted was reported for the first time by
L.J. Stadler
7. Chemical mutagenesis was first reported by
Auerback (1944)
8. Double nullisomy is
2n-2-2
9. Trisomis were first reported by Blakeslee in
Datura Stramonium
10. All possible tetrasomics are available in ……………………… plant
Wheat
11. The kind of Aneuploid are usually lethal are
Nullisomy
12. The alkaloid used to induce polyploidy is
Colchicine
13. Raphano brassicas the sterile hybrid of Radish & Cabbage was produced by
G.D. Karpechenko (1927)
14. The cross between hexaploid wheat Triticum aestivum and rye produced is a
Octoploidy
15. Colchicine is extracted from the root and corms of
Colchicum autumnale
16. Who first reported duplication in drosophila
Bridges (1919)
17. In which types of cells chromosomal aberration is commonly found?
Cancer cells
18. Recombination frequencies are the same for
CIS and trans heterozygotes
19. The map distance between gene A and B is 3 units between B & C is 10 units and between C & A is 7 units – the order of genes in a linkage map constructed on the about would perhaps be
B-A-C
20. The percentage of crossing over will be more if
Linked genes are located apart from each other
21. A point mutation that changes an amino acid coding codon into a stop codon, prematurely terminating synthesis of the encoded protein ………………………
Nonsense mutation
22. Single base change in DNA is known as ………………………
Point mutation
23. Genetic change in a non-sex cell is known as
Somatic mulalion
24. A duplicated DNA sequence next to the original sequence is known as
Tandem duplication
25. A missing sequence of DNA or part of a chromosome
Deletion mutation
26. Mutation that alters the genes reading frame is known as
Frame shift mutation
27. A single base change mutation that alters and amino acid ………………………
Missense
28. A substance that changes, adds, or deletes a DNA base
Multagen
29. The mutation that introduces a section of aminoacids not normally found is known as ………………………
Frame shift mutation
30. A mutation that changes an adenine to guanine is an example of a ………………………
transition
31. A point mutation that has no obvious effect at all on the phenotype is called a ……………………… mutation
silent
32. A point mutation that changes a codon specifying an amino acid into a stop codon is called a ………………………
Non sense mutation
33. Changing the codon AGC to AGA represents ……………………… of a point mutation
missense
34. A point multation that alters a codon so that the encoded aminoacid is substituted with another is called a ………………………mutation
missense
35. A ………………………mutation occurs during the DNA replication that precedes meiosis. while a ……………………… mutation occurs during the DNA replication that preceeds mitosis.
germline, somatic
36. A mutation that introduction of section of aminoacids not normally found is ………………………
Frame shift mutation.
37. A point mutation altering a purine to pyrimidine or vice versa is ………………………
transversion
38. A spontaneous mutation usually originates as an error in ………………………
DNA replication
39. The codon for leucine is CUC. How many different aminoacids could possibly result from a single base substitution
7
40. How may map units separate two alleles if the recombination frequency is o.o7?
7cM
41. In a population of 1000 individuals 360 belong to genotype AA. 480 to Aa and the remaining 160 to aa – Based on the data, the frequency of allela A in the population is
0.7
II. Find out the incorrect statement
* Tetraploidy: Crosses between diploid wheat and rye.
* Hexaploidy: Crosses between tetraploid wheat Triticum durum (macaroni wheat) and rye.
* Octoploidy: Crosses between hexaploid wheat T. aestivum (bread wheat) and rye. Hexaploidy Triticale hybrid plants
12th Bio Botany Guide Chromosomal Basis of Inheritance Additional Important Questions and Answers
I. Fill in the blanks
1. The scientists who independently rediscovered mendelian works were
De Vries, Correns & Tschermak
2. The worm-shaped cells formed during cell division are called in the earlier period as
Chromosomes
3. Who postulated that the chromosomes of a cell are responsible for transferring heredity
Wilhelm Roux (1883)
4. ……………………… was the first to find out physical mutagen in Drosophila
Muller (1927)
5. ………………………used X-rays for the first time to induce mutation in the fruit fly
H.J. Muller
6. Induced mutations are planted was reported for the first time by
L.J. Stadler
7. Chemical mutagenesis was first reported by
Auerback (1944)
8. Double nullisomy is
2n-2-2
9. Trisomis were first reported by Blakeslee in
Datura Stramonium
10. All possible tetrasomics are available in ……………………… plant
Wheat
11. The kind of Aneuploid are usually lethal are
Nullisomy
12. The alkaloid used to induce polyploidy is
Colchicine
13. Raphano brassicas the sterile hybrid of Radish & Cabbage was produced by
G.D. Karpechenko (1927)
14. The cross between hexaploid wheat Triticum aestivum and rye produced is a
Octoploidy
15. Colchicine is extracted from the root and corms of
Colchicum autumnale
16. Who first reported duplication in drosophila
Bridges (1919)
17. In which types of cells chromosomal aberration is commonly found?
Cancer cells
18. Recombination frequencies are the same for
CIS and trans heterozygotes
19. The map distance between gene A and B is 3 units between B & C is 10 units and between C & A is 7 units – the order of genes in a linkage map constructed on the about would perhaps be
B-A-C
20. The percentage of crossing over will be more if
Linked genes are located apart from each other
21. A point mutation that changes an amino acid coding codon into a stop codon, prematurely terminating synthesis of the encoded protein ………………………
Nonsense mutation
22. Single base change in DNA is known as ………………………
Point mutation
23. Genetic change in a non-sex cell is known as
Somatic mulalion
24. A duplicated DNA sequence next to the original sequence is known as
Tandem duplication
25. A missing sequence of DNA or part of a chromosome
Deletion mutation
26. Mutation that alters the genes reading frame is known as
Frame shift mutation
27. A single base change mutation that alters and amino acid ………………………
Missense
28. A substance that changes, adds, or deletes a DNA base
Multagen
29. The mutation that introduces a section of aminoacids not normally found is known as ………………………
Frame shift mutation
30. A mutation that changes an adenine to guanine is an example of a ………………………
transition
31. A point mutation that has no obvious effect at all on the phenotype is called a ……………………… mutation
silent
32. A point mutation that changes a codon specifying an amino acid into a stop codon is called a ………………………
Non sense mutation
33. Changing the codon AGC to AGA represents ……………………… of a point mutation
missense
34. A point multation that alters a codon so that the encoded aminoacid is substituted with another is called a ………………………mutation
missense
35. A ………………………mutation occurs during the DNA replication that precedes meiosis. while a ……………………… mutation occurs during the DNA replication that preceeds mitosis.
germline, somatic
36. A mutation that introduction of section of aminoacids not normally found is ………………………
Frame shift mutation.
37. A point mutation altering a purine to pyrimidine or vice versa is ………………………
transversion
38. A spontaneous mutation usually originates as an error in ………………………
DNA replication
39. The codon for leucine is CUC. How many different aminoacids could possibly result from a single base substitution
7
40. How may map units separate two alleles if the recombination frequency is o.o7?
7cM
41. In a population of 1000 individuals 360 belong to genotype AA. 480 to Aa and the remaining 160 to aa – Based on the data, the frequency of allela A in the population is
0.7
II. Find out the incorrect statement
c) The Homologus chromosomes segregate in metaphase I, thereby separating two different alleles.
c) The Homologus chromosomes segregate in metaphase I, thereby separating two different alleles.
d) If the genes are present on the same chromosome, they undergo more than one crossover in every meiosis.
d) If the genes are present on the same chromosome, they undergo more than one crossover in every meiosis.
c) Both males and females are with red eye
V. Find the Odd man out with reference to Allopolyploidy
c) Both males and females are with red eye
V. Find the Odd man out with reference to Allopolyploidy
d) Induced chromosomal aberration
d) Induced chromosomal aberration
a) 44 and 49
a) 44 and 49
a) linked genes
XI. Assertion (A) & Reason (R)
a) linked genes
XI. Assertion (A) & Reason (R)
b) They have four or six copies of its own genome – induced by doubling of the diploid species.
VI. Find the Odd man out with reference to Altotriploidy
b) They have four or six copies of its own genome – induced by doubling of the diploid species.
VI. Find the Odd man out with reference to Altotriploidy
c) It is directly proportional to the frequency of recombination between them.
VIII. Choose the wrongly matched pair
c) It is directly proportional to the frequency of recombination between them.
VIII. Choose the wrongly matched pair
c
IX. Choose the incorrect statement with reference to Deletion
c
IX. Choose the incorrect statement with reference to Deletion
b) (A) is correct, (R) is the correct explanation (A)
b) (A) is correct, (R) is the correct explanation (A)
a) If both the Assertion (A) & Reason (R) are true and the reason is a correct explanation of the Assertion..
a) If both the Assertion (A) & Reason (R) are true and the reason is a correct explanation of the Assertion..
c) Assertion (A) is true but Reason (R) is false
XII. Two Marks
c) Assertion (A) is true but Reason (R) is false
XII. Two Marks
It states the Mendelian factors (genes) have specific locus on chromosomes & they carry information from one generation to the next generation.
It states the Mendelian factors (genes) have specific locus on chromosomes & they carry information from one generation to the next generation.
1) Ophioglossum 2) Arabiodopsis 3) Sugarcane 4) Rice 5) Potato 6) Maize
1) -1262;
2) -10;
3) 80;
4) 24;
5) 48;
6) 20
1) Ophioglossum 2) Arabiodopsis 3) Sugarcane 4) Rice 5) Potato 6) Maize
1) -1262;
2) -10;
3) 80;
4) 24;
5) 48;
6) 20
- Some junk DNA is made up of pseudogenes, once working but have lost their ability to make proteins.
- They are fossilized parts act as evidence for evolution.
- Some junk DNA is made up of pseudogenes, once working but have lost their ability to make proteins.
- They are fossilized parts act as evidence for evolution.
- His works on Drosophila melanogaster – Sex linkage – helped to confirm chromosome theory of heredity.
- He received Nobel prize in Physiology of medicine in 1933 fot it.
- He coined the term crossing over.
- His works on Drosophila melanogaster – Sex linkage – helped to confirm chromosome theory of heredity.
- He received Nobel prize in Physiology of medicine in 1933 fot it.
- He coined the term crossing over.
Compounds which are not having own mutagenic properties – but enhance the effects of known mutagens.
Eg. Ascorbic acid – increase the damage caused by hydrogen peroxide.
Caffeine – increase the toxicity of methotrexate.
Compounds which are not having own mutagenic properties – but enhance the effects of known mutagens.
Eg. Ascorbic acid – increase the damage caused by hydrogen peroxide.
Caffeine – increase the toxicity of methotrexate.
Eupoidy:
* Ploidy involving entire sets of chromosomes is known as euploidy
* Triploidy (3x); Tetraploidy (4x); Poly ploidy ( ∞n)
Aneuploidy:
* Here the diploid number is altered either by addition or deletion of one or more chromosomes
* Trisomy; Tetrasomv; Monosomy; Nullisomy (2n+1)(2n+2)(2n-1)(2n-2)
Eupoidy:
* Ploidy involving entire sets of chromosomes is known as euploidy
* Triploidy (3x); Tetraploidy (4x); Poly ploidy ( ∞n)
Aneuploidy:
* Here the diploid number is altered either by addition or deletion of one or more chromosomes
* Trisomy; Tetrasomv; Monosomy; Nullisomy (2n+1)(2n+2)(2n-1)(2n-2)
Monoploidy
In Monoploidy the chromosome number is referred as x.
Eg.
Hexaploidy wheat
(2n) = 6 x = 72
haplaid = (n) 36
Monoploidy = x = 12
Haploidy:
Half the number of somatic chromosomes is referred as gametic chromosome number called haploidy (n) Human of haploid = 23 (n) Wheat of haploid = 36 (n)
Monoploidy
In Monoploidy the chromosome number is referred as x.
Eg.
Hexaploidy wheat
(2n) = 6 x = 72
haplaid = (n) 36
Monoploidy = x = 12
Haploidy:
Half the number of somatic chromosomes is referred as gametic chromosome number called haploidy (n) Human of haploid = 23 (n) Wheat of haploid = 36 (n)
Independent assortment
Linkage
1. Genes present in different chromosome they assort independently
Genes present in same chromosome tend to stay together
2. More parental combinations & less new combinations are possible
More parental combinations are possible
Independent assortment
Linkage
1. Genes present in different chromosome they assort independently
Genes present in same chromosome tend to stay together
2. More parental combinations & less new combinations are possible
More parental combinations are possible
- The strength of linkage increases as the distance between linked genes decreases.
- The linkage becomes weaker with the increase in the distance between genes.
- The strength of linkage increases as the distance between linked genes decreases.
- The linkage becomes weaker with the increase in the distance between genes.
- During Synapsis homologous chromosomes come together side by side resulting in bivalents
- As the stage during which each bivalent has 4 chromatids & the stage is known as tetrad stage.
- During Synapsis homologous chromosomes come together side by side resulting in bivalents
- As the stage during which each bivalent has 4 chromatids & the stage is known as tetrad stage.
In this segments of DNA one broken and recombined to produce new combination of alleles – known as Recombination.
In this segments of DNA one broken and recombined to produce new combination of alleles – known as Recombination.
The frequency with which recombination occur is a certain condition
The frequency with which recombination occur is a certain condition
The formula 2n is applied – Organism hetr oizy gous f or 4 loci = n = 4.
So 2n = 24 = 2 x 2 x 2 x 2 = 16.
The organism produces 16 types of gametes.
The formula 2n is applied – Organism hetr oizy gous f or 4 loci = n = 4.
So 2n = 24 = 2 x 2 x 2 x 2 = 16.
The organism produces 16 types of gametes.
- Alkaloid, extracted from – root and corms of colchicum autumnale
- In low concentration to the growing lips it induce polyploidy
- It does not affect the source plant due to the presence of Anticolchicine
- Alkaloid, extracted from – root and corms of colchicum autumnale
- In low concentration to the growing lips it induce polyploidy
- It does not affect the source plant due to the presence of Anticolchicine
- Polyploids – More vigorous & more adaptive
- Ornamental flowers – (Autotetraploids) larger flowers – longer flowering duration
- Increase in fresh weight (due to more water content)
- Aneuploids – help to determine the phenotypic effects (loss or gain of different chromosomes
- Allopolyploids of angiosperms play a role in an evolution of plants.
- Polyploids – More vigorous & more adaptive
- Ornamental flowers – (Autotetraploids) larger flowers – longer flowering duration
- Increase in fresh weight (due to more water content)
- Aneuploids – help to determine the phenotypic effects (loss or gain of different chromosomes
- Allopolyploids of angiosperms play a role in an evolution of plants.
Mendelian disorder:
Occur due to mutation of single gene & follow the well known Mendelian pattern of inheritance.
Eg. Sickle cell anaemia
Chromosomal disorder:
Chromosomal disorders are produced due to alteration in the number of chromosomes.
Eg. Down syndrome
Mendelian disorder:
Occur due to mutation of single gene & follow the well known Mendelian pattern of inheritance.
Eg. Sickle cell anaemia
Chromosomal disorder:
Chromosomal disorders are produced due to alteration in the number of chromosomes.
Eg. Down syndrome
- This numerical chromosomal abnormality is known as double monosomy (2n-l-l)
- From a diploid set of chromosome if one chromosomes is lost, the condition is known as monosomy (2n-l)
- If another chromosome is also lost it is known as double monosomy (2n-l-l)
- This numerical chromosomal abnormality is known as double monosomy (2n-l-l)
- From a diploid set of chromosome if one chromosomes is lost, the condition is known as monosomy (2n-l)
- If another chromosome is also lost it is known as double monosomy (2n-l-l)
Linkage
* It is the tendency of genes in a chromosome to stay close together
* It involves same chromosome of homologous chromosome
* It reduces new gene combinations
* Not very significant in evolution
Crossing over:
* It leads to separation of linked gene
* It involves exchange of segments between nonsister chromatids of homologous chromosome.
* It increases – variability by forming new combinations → lead to formation of new organism
* play important role in evolution
Linkage
* It is the tendency of genes in a chromosome to stay close together
* It involves same chromosome of homologous chromosome
* It reduces new gene combinations
* Not very significant in evolution
Crossing over:
* It leads to separation of linked gene
* It involves exchange of segments between nonsister chromatids of homologous chromosome.
* It increases – variability by forming new combinations → lead to formation of new organism
* play important role in evolution
- The non – sister chromatids of homologous pair make a contact at one or more points.
- These points of contact between non-sister chromatids of homologous chromosomes are called chiasmata.
- The non – sister chromatids of homologous pair make a contact at one or more points.
- These points of contact between non-sister chromatids of homologous chromosomes are called chiasmata.
When any of the three or more allelic forms of a gene occupy the same locus in a given pair of homologous chromosomes, they are said be called multiple alleles.
When any of the three or more allelic forms of a gene occupy the same locus in a given pair of homologous chromosomes, they are said be called multiple alleles.
- About 94% of all flowering plants have only one type of individual, which produces flowers with male organs (the stamens) and female organs (the carpels).
- Such plants are termed as sexually monomorphic.
- About 94% of all flowering plants have only one type of individual, which produces flowers with male organs (the stamens) and female organs (the carpels).
- Such plants are termed as sexually monomorphic.
Some 6% of flowering plants which have two separate sexes are called dimorphic.
XIII. Three Marks
Some 6% of flowering plants which have two separate sexes are called dimorphic.
XIII. Three Marks
Tetrasomy
Tetraploidy
Addition of a pair or two individual chromosomes to diploid set is called Tetrasomy. (2n + 2)
Tetraploids have four eopies of its own genome. They can be induced by doubling the chromosomes of a diploid species.
(2n + 2 + 2) This condition is known as double tetrasomy
There are two types Auto & Allotetraploidy
Eg: wheat
Eg: Grapes, ground nut, potato & coffee
Tetrasomy
Tetraploidy
Addition of a pair or two individual chromosomes to diploid set is called Tetrasomy. (2n + 2)
Tetraploids have four eopies of its own genome. They can be induced by doubling the chromosomes of a diploid species.
(2n + 2 + 2) This condition is known as double tetrasomy
There are two types Auto & Allotetraploidy
Eg: wheat
Eg: Grapes, ground nut, potato & coffee
Medelian Factors
Chromosom at behaviour
1. Alleles of a factor occur in pair
Chromosomes occur in pair’s
2. Similar or dissimilar alleles of a factor separate during the gamete formation
The homologous chromosomes during meiosis.
3. Mendelian factors can assort independently
The paired chromosomes can separate independently
during meiosis, but the linked genes in the same chromosome normaly do not assort independently.
Medelian Factors
Chromosom at behaviour
1. Alleles of a factor occur in pair
Chromosomes occur in pair’s
2. Similar or dissimilar alleles of a factor separate during the gamete formation
The homologous chromosomes during meiosis.
3. Mendelian factors can assort independently
The paired chromosomes can separate independently
during meiosis, but the linked genes in the same chromosome normaly do not assort independently.
- Alleles of a genotype – found in the same locus of a homologous chromosome (A/a)
- In ‘S’ – Phase of meiotic interphase – the replication of chromosome occur – (two copies of each allele (AA/aa) one on each chromatid
- Anaphase II of meiosis, separation of sister chromatids of homologous chromosomes. So each daughter cell (gamete) carries only a single allele of a character (A), (A), (a) and (a)
- Alleles of a genotype – found in the same locus of a homologous chromosome (A/a)
- In ‘S’ – Phase of meiotic interphase – the replication of chromosome occur – (two copies of each allele (AA/aa) one on each chromatid
- Anaphase II of meiosis, separation of sister chromatids of homologous chromosomes. So each daughter cell (gamete) carries only a single allele of a character (A), (A), (a) and (a)
Coupling
* The two dominant alleles or recessive alleles called repulsion or trans configuration
* It tend to inherit together into same gametes
Repulsion:
* If dominant or recessive alleles are present on occur in the same homologous chromosomes two different but homologous chromosomes.
* If they inherit apart in to different game es are
Coupling
* The two dominant alleles or recessive alleles called repulsion or trans configuration
* It tend to inherit together into same gametes
Repulsion:
* If dominant or recessive alleles are present on occur in the same homologous chromosomes two different but homologous chromosomes.
* If they inherit apart in to different game es are
* During cygotene stage of prophase I of meiosis I – homologous chromosomes are aligned side by side resulting in a pair called (bivalents).
* This pairing phenomenon is called synapsis or syndesis.
Based on the starting poiring of pairing there are 3 types of synapsis
Procentric
Proterminal
Random
Starts from middle
Starts from the telomeres
Starts from any where
* During cygotene stage of prophase I of meiosis I – homologous chromosomes are aligned side by side resulting in a pair called (bivalents).
* This pairing phenomenon is called synapsis or syndesis.
Based on the starting poiring of pairing there are 3 types of synapsis
Procentric
Proterminal
Random
Starts from middle
Starts from the telomeres
Starts from any where
Sharbati sonora:
* Multant variety of Wheat – approved in 1967
* Sonora 64 (Mexican variety subjected to gamma rays to produce sharbati sonora
* Developed by Dr. M.D. Swaminathan
* Early maturing & high protein content high kneading quality
Castor Aruna:
* Mutant castor variety
* Seeds treated with thermal neutrons
* Early maturing – (120 days instead of 270 dyas) & High yielding.
Sharbati sonora:
* Multant variety of Wheat – approved in 1967
* Sonora 64 (Mexican variety subjected to gamma rays to produce sharbati sonora
* Developed by Dr. M.D. Swaminathan
* Early maturing & high protein content high kneading quality
Castor Aruna:
* Mutant castor variety
* Seeds treated with thermal neutrons
* Early maturing – (120 days instead of 270 dyas) & High yielding.
Rise temperature breaks the hydrogen bonds between two DNA nucleotides – & affects the process of replication & transcription.
Rise temperature breaks the hydrogen bonds between two DNA nucleotides – & affects the process of replication & transcription.
Ionizing radiation:
* Short wave length and carry enough higher energy to ionize electrons from atoms. They breaks the chromosome & chromatids. Ex. x-rays – gamma rays, alfa rays, beta rays & cosmic rays.
Non Ionizing radiation:
* Longer wave lengths and carry lower energy so they have lover penetrating power used to treat unicellular microbes – spores pollengrains – which have nuclei – near surface membrance. Eg. UV rays
Ionizing radiation:
* Short wave length and carry enough higher energy to ionize electrons from atoms. They breaks the chromosome & chromatids. Ex. x-rays – gamma rays, alfa rays, beta rays & cosmic rays.
Non Ionizing radiation:
* Longer wave lengths and carry lower energy so they have lover penetrating power used to treat unicellular microbes – spores pollengrains – which have nuclei – near surface membrance. Eg. UV rays
- Many polyploids are more vigorous and more adaptable than diploids.
- Many ornamental plants are autotetraploids and have large flower and longer flowering duration than diploids.
- Auto polyploids usually have increase in fresh weight due to more water content.
- Aneuploids are useful to determine the phenotypic effects of loss or gain of different chromosome.
- Many angiosperms are allopolyploids and they play a role in an evolution of plants.
- Many polyploids are more vigorous and more adaptable than diploids.
- Many ornamental plants are autotetraploids and have large flower and longer flowering duration than diploids.
- Auto polyploids usually have increase in fresh weight due to more water content.
- Aneuploids are useful to determine the phenotypic effects of loss or gain of different chromosome.
- Many angiosperms are allopolyploids and they play a role in an evolution of plants.
Chemical which include mutation are called mutagens.
Example:
Nitrous oxide alters the nitrogen bases of DNA and disturb the replication and transcription that leads to the formation of incomplete and defective polypeptide during translation.
Chemical which include mutation are called mutagens.
Example:
Nitrous oxide alters the nitrogen bases of DNA and disturb the replication and transcription that leads to the formation of incomplete and defective polypeptide during translation.
The two dominant alleles or recessive alleles occur in the same homologus chromosomes, tend to inherit together into same gamete are called coupling (or) cis configuration
XIV. Five Marks
The two dominant alleles or recessive alleles occur in the same homologus chromosomes, tend to inherit together into same gamete are called coupling (or) cis configuration
XIV. Five Marks
- T.H. Morgan works on fruit fly supported the chromosomal theory of inheritance.
- The alleles for red or white eye colour are present on the X – chromosome but there is no counter part for this gene on the Y chromosome.
- The genes for yellow body colour and miniature wings are also carried on the X – chromosome.
- By understanding the sex linked inheritance of these characters it is proved that genes are located on the chromosomes.
- Thus T.H. Morgan’s works on Drophila came as a support to the chromosomal theory of inheritance.
- T.H. Morgan works on fruit fly supported the chromosomal theory of inheritance.
- The alleles for red or white eye colour are present on the X – chromosome but there is no counter part for this gene on the Y chromosome.
- The genes for yellow body colour and miniature wings are also carried on the X – chromosome.
- By understanding the sex linked inheritance of these characters it is proved that genes are located on the chromosomes.
- Thus T.H. Morgan’s works on Drophila came as a support to the chromosomal theory of inheritance.
* Homologous DNA molearles are paired side by side with their duplicated copies of DMAs.
* One strand of both DNAs cut in one place by the enzyme endonuclease.
* The cut strands cross & join the homologous strands forming the Holliday junction
* Holliday junction – migrates away from the original site, by branch migration – as a result
heteroduplex region is formed.
* DNA strands may cut along the vertical (V) or horizontal (H) line.
* The vertical cut will result in heteroduplexes with recombinants & the Horizontal with non recombinants.
* Homologous DNA molearles are paired side by side with their duplicated copies of DMAs.
* One strand of both DNAs cut in one place by the enzyme endonuclease.
* The cut strands cross & join the homologous strands forming the Holliday junction
* Holliday junction – migrates away from the original site, by branch migration – as a result
heteroduplex region is formed.
* DNA strands may cut along the vertical (V) or horizontal (H) line.
* The vertical cut will result in heteroduplexes with recombinants & the Horizontal with non recombinants.
* C.E Allen (1917) discovered sex determination in plants.
* Complex precess determined by
* genes
* environment
* hormones
Sex determination silene latifolia – is controlled by 3 distinct regions in a sex chromosome
* Y – Chromosome – determines maleners
* X – Chromosome – specify femaleness
* X & Y – show different segments (I, II, III, IV, & V)
* C.E Allen (1917) discovered sex determination in plants.
* Complex precess determined by
* genes
* environment
* hormones
Sex determination silene latifolia – is controlled by 3 distinct regions in a sex chromosome
* Y – Chromosome – determines maleners
* X – Chromosome – specify femaleness
* X & Y – show different segments (I, II, III, IV, & V)
- Carica papaya 2n = 36
- The sex chromosomes look like autosomes
- Developed from autosomes
- Y- chromosome carries the genes for male organ
- X- chromosomes bear the gene for female organ development.
- Carica papaya 2n = 36
- The sex chromosomes look like autosomes
- Developed from autosomes
- Y- chromosome carries the genes for male organ
- X- chromosomes bear the gene for female organ development.
- gametophyte – haploid with 8 chromosome (n).
- The sporophyte – diploid & heterogametic
- Male sfemale gameto phyte – seven autosomes are similar.
- In female 8th chromosome is X – Larger than the seven autosomes.
- In male 8th chromosome is Y – Smaller than the autosomes.
- In sporophyte – contain XY – combinations produces two types of meiospores
- Meiospore with X – produce – female gemetophyte
- gametophyte – haploid with 8 chromosome (n).
- The sporophyte – diploid & heterogametic
- Male sfemale gameto phyte – seven autosomes are similar.
- In female 8th chromosome is X – Larger than the seven autosomes.
- In male 8th chromosome is Y – Smaller than the autosomes.
- In sporophyte – contain XY – combinations produces two types of meiospores
- Meiospore with X – produce – female gemetophyte
Genotypes of the parents are Ad/ Ad x aD x aD – If genes are so tightly linked, the only possible types of gametes produced by parents are
Ad and aD respectively (parental or nonrecombinant gametes)
FI will be all Ad / aD
only types of gametes from each FI can be Ad (50%)oraD(50%)
F2 frequencies can be calculated from these F2 will be Ad/ Ad (1/4i) Ad/ aD (1/2) aD / aD (1/4)
Genotypes of the parents are Ad/ Ad x aD x aD – If genes are so tightly linked, the only possible types of gametes produced by parents are
Ad and aD respectively (parental or nonrecombinant gametes)
FI will be all Ad / aD
only types of gametes from each FI can be Ad (50%)oraD(50%)
F2 frequencies can be calculated from these F2 will be Ad/ Ad (1/4i) Ad/ aD (1/2) aD / aD (1/4)
Definition:
Mutation affecting single base or base pair of DNA
Types:
* Indel mutation: (Base pair insertions or. addition. Addition or deletions of nucleotide
pairs.
* Substitution: one base pair is replaced by another
Types – (Two)
* (Purine replaced by Purine)
* Pyrimidine replaced by Pyrimidine
* Transversion purine replaced by pyrimidin or pyridine replaced
Synonymous or silent mutations:
Here change in one codon for an amino acid into another codon for that same amino acid
Missense or Non synonymous mutations
Here the codon for one amino acid is changed in to -a termination or stop codon.
Frameshift mutations.
Additions or deletions of a single base pair of DNA, – changed the reading frame for translation – so there is complete loss of normal protein structure & function.
Definition:
Mutation affecting single base or base pair of DNA
Types:
* Indel mutation: (Base pair insertions or. addition. Addition or deletions of nucleotide
pairs.
* Substitution: one base pair is replaced by another
Types – (Two)
* (Purine replaced by Purine)
* Pyrimidine replaced by Pyrimidine
* Transversion purine replaced by pyrimidin or pyridine replaced
Synonymous or silent mutations:
Here change in one codon for an amino acid into another codon for that same amino acid
Missense or Non synonymous mutations
Here the codon for one amino acid is changed in to -a termination or stop codon.
Frameshift mutations.
Additions or deletions of a single base pair of DNA, – changed the reading frame for translation – so there is complete loss of normal protein structure & function.
crossing over
Translocation
It is an exchange of genetic material between homologous chromosomes that occurs during Prophase I of meiosis during gametes formation
It is a genetic abnormality involving the exchange of fragments of genes between
non-homologous chromosomes
It is a normal event occurring in almost all sexually reproducting organisms.
It is a chromosomal aberration.
It often produces recombinations which play important role in evolution.
It rarely produces recominations.
crossing over
Translocation
It is an exchange of genetic material between homologous chromosomes that occurs during Prophase I of meiosis during gametes formation
It is a genetic abnormality involving the exchange of fragments of genes between
non-homologous chromosomes
It is a normal event occurring in almost all sexually reproducting organisms.
It is a chromosomal aberration.
It often produces recombinations which play important role in evolution.
It rarely produces recominations.
* There are 2 types
* Deletion
* Duplication
Deletion or Deficiency:
* (loss of a portion of chromosome)
* 2 types
* Terminal deletion (break in any one end
* Intercalary deletion (two breaks & reunion of terminal parts leaving the middle.
* > Unpaired loops some times formed known as deficiency loops (during meiotic prophase)
* > Larger deletions may have lethal effect Duplication or Repeat
* > Same order of genes repeated more than once in the same chromosome.
Eg. Drosophila
Duplication
3 types
* Tandem duplication
* Reverse tandem
* Displaced duplication
i) Tandem duplication
Duplicated segment is located immediately after the normal segment in the same order.
ii) Reverse tandem
Duplicated segment, immediately after the normal segment but gene sequence order will be reversed.
ii) Reverse tandem
Duplicated segment away from the normal segment.
Duplication play a maj or role in evolution.
* There are 2 types
* Deletion
* Duplication
Deletion or Deficiency:
* (loss of a portion of chromosome)
* 2 types
* Terminal deletion (break in any one end
* Intercalary deletion (two breaks & reunion of terminal parts leaving the middle.
* > Unpaired loops some times formed known as deficiency loops (during meiotic prophase)
* > Larger deletions may have lethal effect Duplication or Repeat
* > Same order of genes repeated more than once in the same chromosome.
Eg. Drosophila
Duplication
3 types
* Tandem duplication
* Reverse tandem
* Displaced duplication
i) Tandem duplication
Duplicated segment is located immediately after the normal segment in the same order.
ii) Reverse tandem
Duplicated segment, immediately after the normal segment but gene sequence order will be reversed.
ii) Reverse tandem
Duplicated segment away from the normal segment.
Duplication play a maj or role in evolution.
a) The problem involves an understanding of linkage, crossing over & independent assortment.
F 2 geno & phenotypic ratio =
b) When crossing over occurs the result in same as the question (a)
F 2 geno & phenotypic ratio =
c) When a & b linked with out crossing on the heterozygolic parent can be AB / ab – (cis) or Ab / ab – (tr ans)
However there won’t be any recombinant gametes because no. crossing over occur.
It will produce Ab & aB (50 % of each)
The progeny of test cross will be Ab/ ab&aB/ab
a) The problem involves an understanding of linkage, crossing over & independent assortment.
F 2 geno & phenotypic ratio =
b) When crossing over occurs the result in same as the question (a)
F 2 geno & phenotypic ratio =
c) When a & b linked with out crossing on the heterozygolic parent can be AB / ab – (cis) or Ab / ab – (tr ans)
However there won’t be any recombinant gametes because no. crossing over occur.
It will produce Ab & aB (50 % of each)
The progeny of test cross will be Ab/ ab&aB/ab