Select the TWO correct statements 1 If the trait is autosoma

Select the TWO correct statements:

1. If the trait is autosomal recessive, 1-1 is hetero and 1-2 is homo.

2. If the trait is sex linked and recessive, then 1-1 and 1-2 are heterozygous.

3. If the trait is sex linked and dominant, then 1-1 and 1-2 are heterozygous.

4. If the trait is sex linked and dominant, then 1-1 hetero. and 1-2 homo.

5. If the trait is autosomal dominant, 1-1 is homo. and 1-2 is hetero.

6. If the trait is sex linked and dominant, then 1-1 is hetero. and 1-2 is homo.

A little confused about the fact that the pedigrees are not connected, what does this imply?

Thanks in advance for the chance to learn,

Max

550 -O-T -o

Solution

Based on the pedigree picture above one can say the trait can be autosomal recessive.A gene present on both of the non-sex chromosomes set should be in recessive condition for the trait to be expressed.If one examine closely only the females are affected but not the males.And in the next generation in the second picture both females and males are equally affected proving that its not sex-linked.This is possible only when the males are in heterozygous condition for the gene and females have two copies resulting in upto 50% affected progeny. It could also be autosomal dominant, which means only a single copy of the gene responsible for the disease is enough to bring put the expression of the trait.In that case the parents since males are unaffected they will be in homozygous condition for the proper allelic form of gene and females if when homozygous all the progeny will be affected.But if they are heterozygous for the gene they only 50% of the progeny are affected. Hence statements 1 & 5 hold true based on the second picture. Yes pedigrees mentioned in the question are not connected as the first one is not showing any affected individuals which should have been 50% .Based on first pedigree one can only say that the gene is autosomal recessive and the females have only copy of gene thus none of the progeny are affected.But according to the second one either the female is homo with two copies or both are hetero with the 50% of progeny affected.