Question

Problems –

A. George has come to see you as a genetic counselor for advice. George has rare autosomal dominant trait that causes purple-pigmented hair. He has suffered ridicule during school and into adulthood, that George wants to understand the risk of having a child with purple hair.

You are an expert in this rare trait that produces purple hair. While the gene that encodes the enzyme to produce the purple hair has not been identified, you have identified a DNA marker that is 20 map units away from the purple hair dominant allele. The DNA marker is called P2.

You also know that the allele that encodes the enzyme to produce brown hair (recessive allele) is 20 map units away from another DNA marker called B1.

In your genetic lab, you can test for the DNA markers, P2 and B1, which is the genetic test that George wants. You also test George’s Dad who has purple hair and his mom who has brown hair.

George’s Dad has only the P2 DNA marker and purple hair. George’s mom has only the B1 marker and brown hair.

(10 points).George has both the P2 and B1 marker and also has purple hair. What are the parental chromosomes that George inherited from his Dad? From his Mom? Which DNA markers are linked to which alleles for the hair color? Diagram the parental chromosomes below including alleles for hair color and DNA markers

(15 points) George asks you if he has his sperm tested and selects sperm for artificial insemination that have only B1 DNA marker then he cannot pass autosomal dominant purple hair gene onto his children. Is he correct? Why or why not? George is a visual learner so feel free to diagram the chromosomes that include the DNA markers and alleles for purple or brown hair color and their percentage to better explain your answer to George.

Answer 1

The P2 marker is found at 20 m.u. from purple allele.

The B1 marker is found at 20 m.u. from brown allele.

Please look in image:

Dad Purple Mother Brown BL Pa 1 4 tai tt р - George e pa À BI • * George inherited f f from Dad * " þ BI Mother - * Pe linked to purple color * B, linked to brown color. P P2 George Dada * Parental - 1 P P2 Mother & p Bo p Bi

No, the George is not correct. Becausw the gamete formation is an independent event. Because there are found both kind of gametes. Each bearing P allele and p alelle.

The genetic distance between marker and allele is 20 . This suggests that recombinant gametes are 20 and parental are80%.

. ..! P P2 N L t L P P2 purple 40 7 . I Parentar to B, Brown 40 l p Bi Purple 10 Recombina to P2 Brown 10 gamete - ť B, ant That's why 50% chances that Sperm bears purple allele.