Exam 2: Extensions to Mendels Laws

Suppose you discovered a new mutation in mice that causes a curved spine.You noticed that this mutation is seen only in females.When curved-spine females are crossed with normal males,the progeny are always recovered in the ratio: 1/3 curved-spine females,1/3 normal females,1/3 normal males.Explain the genetic basis for this ratio.

In humans,XO individuals are females with Turner syndrome and XXY individuals are males with Klinefelter syndrome.Red-green colour blindness is caused by an X-linked recessive allele.Suppose a colour-blind man and a normal woman with no family history of colour blindness married and had a daughter who was colour-blind and had Turner syndrome.Which event could have given rise to this offspring?

Which of the following observations was made in the mid-1800s and implied that the nucleus contains the genetic material?

In fruit flies,brown eyes can be caused by the recessive mutations pn (prune),bw (brown),or ry (rosy),which are on the X chromosome,second chromosome,and third chromosome,respectively.Wild-type alleles for all three genes must be present for eyes to be red.Suppose that two brown-eyed flies are crossed and their progeny consist of brown-eyed sons and red-eyed daughters.Which mutation is responsible for the brown eyes in the parental female?

Which sex chromosomes are limited to only one sex?