Linkage and Recombination I (Lec 9)

Question 1

In regards to pattern baldness, males castrated at an early age rarely become bald, indicating that the trait is clearly stimulated by what?

Answer 1

androgens

Question 2

Early studies suggested that pattern baldness was what type of trait in males and females?

Answer 2

males - autosomal dominant

females - recessive

Question 3

It is suspected that the gene responsible for pattern baldness might be located on the X or Y chromosome?

Answer 3

X

Question 4

The pattern baldness gene is located at position p12-22; this region also includes what?

Answer 4

the androgen-receptor gene which encodes a protein that binds androgens

Question 5

Are linked genes located close together on the same chromosome?

Answer 5

yes

Question 6

True or false?

Linked genes assort independently

Answer 6

false, do not assort independently

Question 7

Compared to linkage, which keeps genes together, crossing over does what?

Answer 7

mixes up genes

Question 8

When does crossing over take place and what is it responsible for?

Answer 8

during meiosis, responsible for recombination

Question 9

MD/md x md/md -> 1/2 MD/md and 1/2 md/md

Are the genes in this test cross linked?

Answer 9

yes; gametes that contain only original combinations of alleles presents in the parents are non recombinant gametes (MD and md)

Question 10

MMDD x mmdd -> MmDd
Mm/Dd x md/md -> 1/4 MmDd, 1/4 MmDd, 1/4 mmdd, 1/4 Mmdd and 1/4 mm/Dd
Are the genes in this test cross linked?

Answer 10

no; MD and md are non recombinant gametes; Md and mD are recombinant gametes; MmDd and mmdd are non recombinant progeny; Mmdd and mmDd are recombinant progeny

Question 11

After a single crossover has taken place, gametes that receive two chromatids that did not participate are called what?

Answer 11

nonrecombinants

Question 12

After a single crossover has taken place, gametes that receive two chromatids that participated in the crossing over are called what?

Answer 12

recombinants

Question 13

If there is no crossing over, what type of gametes are produced?

Answer 13

only non recombinant gametes

Question 14

True or False?

The frequency of recombinant gametes is always half the frequency of crossing over.

Answer 14

true

Question 15

What is the maximum proportion of recombinant gametes?

Answer 15

50%

Question 16

A single crossover produces how many non recombinant gametes and how many recombinant gametes?

Answer 16

half and half

Question 17

of recombinant progeny/total # of progeny x 100% = ?

Answer 17

recombination frequency

Question 18

When wild-type alleles are found on one chromosome and mutant alleles are found on the other chromosome (p+b+/pb), this is called what?

Answer 18

coupling

Question 19

When one chromosome carries a wild type allele and a mutant allele and the other carries the other wild type allele and the other mutant allele (p+b/pb+), this is called what?

Answer 19

repulsion

Question 20

Thomas Hunt Morgan was a key player in the study of what?

Answer 20

sex linked inheritance

Question 21

Sturtevant had the idea that variation in the strength of linkage might indicate what?

Answer 21

how genes are positioned along a chromosome

Question 22

Calvin Bridges demonstrated that nondisjunciton of X chromosomes was related to what?

Answer 22

inheritance of eye color in drosophila