Question

Question 1 1 pts Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype? O a person with an extra X chromosome Turner syndrome, 45, X O Down syndrome, 46, XX O a person with one normal and one shortened (deleted) X O translocation of SRY to an autosome of a 46, XX individual Question 2 1 pts What does a frequency of recombination of 50% indicate? O Independent assortment is hindered O The two genes are likely to be located on different chromosomes. O Abnormal meiosis has occurred O All of the offspring have combinations of traits that match one of the two parents. O The genes are located on sex chromosomes.

Answer 1

1) SRY gene on the X chromosome is responsible for the development of male reproductive organs, the genotype of normal males is XY and genotype of normal females is XX, that is females do not have Y chromosome, if the SRY gene is translocated to another chromosome, and if the female progeny gets that chromosome with the SRY region, then female develops male reproductive organs so the answer is translocation of SRY to the autosome of a 46,XX

2) the maximum possible recombination frequency is 50%,

let's consider 2 genes A and B located on a different chromosome

the dihybrid was obtained by the cross between AABB and aabb

so in the dihybrid the alleles A and B are on one chromosome and alleles a and b are on another chromosome, so AB and ab are parental type gametes and aB and Ab are recombinant type gametes

the dihybrid AaBb is crossed to aabb

AaBb* aabb

	AB	aB	Ab	ab
ab	AaBb (parental type)	aaBb (recombinant)	Aabb(recombinant)	aabb(parental type)

if the genes are on the different chromosome ( or the genes are not linked that is far apart in a chromosome ) then we expect each class of progeny in equal proportions so

the number of recombinant progenies = number of parental type progenies

recombination frequency= (number of recombinant progenies/total number of progenies )$\times$100

=(2/4)$\times$100

that is if the recombination frequency between 2 genes is 50% then the genes are not linked

so the answer is the two genes are likely to be located on different chromosomes.