Short Answer TypeWhat are 'true breeding lines' that are used to study inheritance pattern of traits in plants?
How does the gene 'I' control ABO blood groups in humans? Write the effect the gene has on the structure of red blood cells.
In humans, the ABO blood groups are controlled by a gene called gene I. It has three alleles, namely IA, IB and i. Two of the three alleles IA and I B dominate over i. But IA and I B express themselves in each other’s presence and hence are co-dominant.
Showing the Genetic Basis of Blood Groups in Human Population is given as follows:
|
Allele from Parent 1 |
Allele from Parent 2 |
Genotype of offspring |
Blood type of offspring |
|
I A |
I A |
I A I A |
A |
|
I A |
I B |
I A I B |
AB |
|
I A |
i |
I A i |
A |
|
I B |
I A |
I A I B |
AB |
|
I B |
I B |
I B I B |
B |
|
I B |
i |
I B i |
B |
|
i |
i |
i i |
O |
These alleles help to determine the structure of the red blood cells. The plasma membrane of red blood cells has sugar polymers that protrude out from its surface and the kind of sugar is regulated by the gene 'I' of ABO blood group. The alleles IA and IB produce A and B types of sugar, while allele i does not produce any sugar. Thus when allele ‘IA and IA’ and ‘I A and i‘ are present together then the red blood cells have sugar A on the surface. When IB and I B or IA and i are present then sugar B is found on the surface. When IA and I B are present both A and B sugar are found on the cell surface. While blood group O does not bear any sugar.
Write the types of sex-determination mechanisms the following crosses show. Give an example of each type
(i) Female XX with Male XO
Write the types of sex-determination mechanisms the following crosses show. Give an example of each type
(ii) Female ZW with Male ZZ
A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child.
Mendel published his work on inheritance of characters in 1865, but it remained unrecognized till 1900. Give three reasons for the delay in accepting his work.
A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms for experiments with shorter life cycle. Provide a reason.
A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible.
Long Answer TypeShort Answer TypeIn a cross between two tall pea plants some of the off-springs produced were dwarf. Show with the help of Punnett square how this is possible.
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