Short Answer TypeMention any two contrasting traits with respect to seeds in pea plant that were studied by Mendel.
In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a)The appearance of pink flowers is not known as blending. Why?(b)What is the phenomenon known as?
Linkage or crossing-over of genes are alternatives of each other. Justify with the help of an example.
Linkage is the tendency for two or more non-allelic genes to be inherited together, because they are located more or less closely on the same chromosome.
Crossing over is the process by which two homologous chromosomes pair up and exchange sections of the coiled DNA.
If linkage is high the crossing over will be low.
If linkage is less the crossing over will be more.
In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male, F1 progeny produced and intercrossed the F2 phenotypic ratio of Drosophila deviated significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located on the ‘X’ chromosome showing high linkage & therefore inherited together, recombinants were formed due to crossing over but at low percentage.
Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.
Identify ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in the table given below :
|
No. |
Syndrome |
Cause |
Characteristic of affected individuals |
Sex Male/Female/ both |
|
1 |
Down’s |
Trisomy of 21 chromosome |
‘a’ (i) (ii) |
‘b’ |
|
2 |
‘c’ |
XXY |
Overall masculine development |
‘d’ |
|
3 |
Turner |
45 with XO |
‘e’ (i) (ii) |
‘f’ |
Name the respective pattern of inheritance where F1 phenotype
(a) does not resemble either of the two parents and is in between the two.
(b) resembles only one of the two parents.
(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.
(b) What is the phenotype of the following:(i) IAi
(ii) i i
Long Answer Type(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?
(a) Why is fertilization in an angiosperm referred to as double fertilisation? Mention the ploidy of the cells involved.
(b) Draw a neat labeled sketch of L.S. of an endospermous monocot seed.
Short Answer TypeA male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.
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