7. The following pedigree shows inheritance of the inability to smell Pseudomona

Question

7. The following pedigree shows inheritance of the inability to smell Pseudomonas bacteria and the inability to roll the tongue into a U-shape Inability to roll the tongue is an autosomal recessive trait. Use A/a for smelling/non-smelling and R/r for rolling/non-rolling inability to roll tongue 10 Consider the inability to smell Pseudomonas and complete the following conclusions (ignoree X-inactivation) (0) The data are consistent/inconsistent with an autosomal dominant mode of inheritance because (ii) The data are consistent/inconsistent with an X-linked recessive mode of inheritance because (ii) The data are consistent/inconsistent with an X-linked dominant mode of inheritance because [4 pts] (b) If the two genes are assorting independently, what is the probability that the first child born to III-4 and III-5 will be a non-smeller, non-roller?

Explanation / Answer

i) and iii) The data is inconsistent with an autosomal dominant mode and X-linked dominant mode because of the following reason

a) any genetic disorder who follow dominant mode ( either autosomal or x-linked) does not skip the generation.

b) if it were the case of autosomal dominant then either one of the parents of III3 should have suffered from the inability of smelling pseudomonas bacteria. similarly, if it were the case of X-linked dominant mode then the mother of both child III3 and III9 should have the trait.

ii) the data is inconsistent with an X- linked recessive mode because if it were the case then the father of child denoted II5 should have the suffer from the inability to smell Pseudomonas bacteria.

iv) both the trait follow the autosomal recessive mode of inheritance

the first child of III4 and III5 will be non-smeller if the child is homozygous for smelling gene as one of the parents have this trait so it depending on the other parent to have that recessive allele to pass on to their first child

therefore probability of being non-smeller = child having recessive gene = (1/2) x (3/4) = 3/8

in case of tongue rolling, the same condition persists as above, so, the probability will be same =3/8

therefore child having both the trait = (3/8) x (3/8) = 9/64 = 14.06%

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