Question

One in 20 people has restless leg syndrome, in which the legs feel tingly or aching nearly all the time, causing great daytime fatigue from interrupted sleep. A gene that confers susceptibility for the condition is on chromosome 12. Another fairly common inherited condition causes extremely red hair and an inability to tan. The person has an unusual variant of the pigment molecule melanin, called “red” melanin. Both restless leg syndrome and red melanin are recessive, and their genes are on different chromosomes.

Suzanne and Michael met at the original Woodstock rock festival in the summer of 1969, drawn to each other because of their striking red hair and very pale skin. Neither has a family history of restless leg syndrome. A few years later they married, and in 1975 they had Marvin and Gary, monozygotic red-headed twins who do not tan.

Jackie and David were at Woodstock too. They each have dark brown hair, and David suffers from restless leg syndrome. Their daughter, Eileen, has dark brown hair and legs that aren’t restless.

Gary and Eileen get together, and they have a son, Todd. He has red hair, doesn’t tan, and has restless leg syndrome.

HINT: the two characters that are discussed in this case study are

1) leg movement, and

2) melanin type

8.   What are the two different traits possible (phenotypes) for each of the characters? (2 pts)

            a. leg movement:        trait 1 is _______________________

                                                trait 2 is _______________________

            b. melanin type:           trait 1 is _______________________

                                                trait 2 is _______________________

9. What are the GENOTYPES possible for each trait? To answer this question, you should list the 4 different traits from question 8, and all of the genotypes that are possible to encode that trait/phenotype. (4 pts)

10. Draw a pedigree including all of the individuals that are a part of this case study. Use the proper symbols, and write out the genotypes of all of the individuals under their symbol (this should be one of the genotypes that you listed for question 9) (16 pts)

11. If two individuals who are dihybrid (di- means two traits; hybrid means heterozygous) for restless leg syndrome and red melanin have children, what is the probability that they would have a child with normal legs and red melanin? For complete points, you must draw out the correct Punnett squares, considering both traits. Use Figures 4.10 and 4.12 to help you answer this. (3 pts)

Answer 1

8) leg movenent : trait 1 is restless leg syndrome

Trait 2 is non restless or normal leg

Melanin type: trait 1 is red hair and pale skin

Trait 2 is dark brown hair and normal skin

Answer 9) genotypes possible for each trait.

For restless leg syndrome ll

For normal leg LL or Ll

For red hair and tan skin - mm

For brown hair and non tan skin - MM/Mm

(I have used L symbol to denote the leg movement and M to denote the melanin type)

Answer 10

Answer 11)