Question

If the pedigree shown is for an autosomal recessive trait, what are the genotypes of individuals II-1, II-6 and II-9, where A- is not kooky and aa is kooky.

| 11 2 3 Ooh 14 5 6

Answer 1

In case of first pedigree

Affected offspring has phenotypically normal parent , hence the parents are heterozygous for that trait ( as the trait is recessive ) . I. e the parents are of A//a genotype and

ii-1 offspring could be either A//A or A//a ( probability of two genotype)

First pedigree Alla lla Total generation - 2 Total individual - 5 Total male - 3 Total female - 2 se Pea - Alla or AllA l la ala affected male-i As the trait I affected female-ol is autosomal recessive (said) and one offspring is affected and the affected of spring has phenotypically normal parent then it is clear that both of the parent are heterozygous for the trait. - Affected offspring is 'aa (as recessive) then one à comes from his father and other ' comes from his mother - therefore the genotype of the parents are 'Aa for both (as both are phenotypically normal & and it is dominant over à :) Aa x Aa. AA (Normal) Aaaa (Phenotypically affected) normal) be genotype of il-l or Aa [AllA on could Alla] Therefore either AA Phe eit

In case of second pedigree

Affected offspring has phenotypically normal parent hence the parents must be heterozygous for the trait i. e A//a therefore

ii-6 has A//a or A//A genotype (probability of two genotype )

- 5 Second Pedigree w Alla oro Alla allad o b (said Total generation 2 Total individual - 5 Total male - 2 Total female - 3 affected male-o affected female - I Alla ALLA fected nt or AllA Alla nt are recessive and are the trait is Autosomal one offspring (11-4) (said) is affected and affected the female has phenotypically normal parent. Hence it is clear that, both Parent are ueterozygous for the trait. Affected offspring's genotype - alla (as it is necessive, only aa Condition make the offspring affected) one 'al of the offspring comes from her mother and another la comes from her father. i.e. both parent campy at least one 'a'. and as they are phenotypically normal, and K is dominant over a then it is clear that the genotype of parents are Alla. there other two offspring (11-5, 11-6) are Phenotypically normal hence they could be either Alla on Alla (11-6 genotype) Aa x Aa AK Aa aa

In case of 3rd pedigree father is affected i.e homozygous for recessive allele a//a and one offspring is affected (a//a) therefore mother must be heterozygous i.e A//a hence

ii-9 has A//a heterozygous genotype (probability of only one genotype )

3rd pedigree Alla OZ alla As the alla trait is Alla Alla autosomal Total generation - 2 Total individual - 5 Total male – 2 Total female - 3 07 08 h 9 affected male - I affected female-1 recessive (said) one Father is affected. Hence genotype of father would be alla (as it is recessive hence only alla condition can affect anyleody) one offspring (11-7) is affected hence the offspring's genotype is alla (as only alla Condition can affect any body) 11-7 Caffected offspring) beceives one à from nes affected father and the other á Games from her mother. i.e her mother is heterozygous - Alla Therefore 1-8 and 11-9 offspring to have Alla genotype. Aa x aa Aa aa (Phenotypically affected) normal) 11-9's genotype - Alla on Aa :