Ch. 7 Linkage and Recombination

Question 1

What is the sorting of alleles into new combinations?

Answer 1

recombination

Question 2

What are genes that are close together on the same chromosome?

Answer 2

linked

Question 3

If crossing over occurs between two genes 100% of the time, what is recombination frequency?

Answer 3

50%

Question 4

The allele combination in the offspring is the same combination as in the parent

Answer 4

nonrecombinant

Question 5

The allele combination in the offspring is different than the combinations in the parent

Answer 5

recombinant

Question 6

In a heterozygote testcross, the offspring of the type of gene results in 4 phenotypes in equal proportions

Answer 6

unlinked

Question 7

In a heterozygote testcross, the offspring of this type of gene results in 4 phenotypes where the nonrecom. > recomb

Answer 7

incompletely linked

Question 8

In a heterozygote testcross, the offspring of this type of gene results in 2 phenotypes in the offspring (both nonrecom.)

Answer 8

completely linked

Question 9

In a heterozygote, the dominant alleles are the same chromosome

Answer 9

coupling
cis

Question 9

What is the maximum recombination frequency?

Answer 9

50%

Question 10

In a heterozygote, the dominant alleles are in the opposite chromosomes

Answer 10

repulsion
trans

Question 11

If the phenotype of the nonrecombinant offspring matches the phenotype of the parents, the alleles are in

Answer 11

coupling

Question 12

If the phenotype of the non recombinant offspring does not match the phenotype of the parents, the alleles are in

Answer 12

repulsion

Question 13

True or False: in incompletely linked genes, there will always be more non recombinants then recombinants

Answer 13

True

Question 14

Which of the following would result in the lowest offspring numbers?

Answer 14

2 crossovers

Question 15

What is the first step in a three-point test cross?

Answer 15

determine gene order

Question 16

How do you determine the middle gene?

Answer 16

compare the non recombinants to double crossovers

Question 17

How do you calculate recombination frequencies?

Answer 17

number of recombinants/total

Question 18

How many numbers do you add together when doing recombination frequency in three-point test cross?

Answer 18

4

Question 19

How do you calculate the expected probability of double crossovers?

Answer 19

multiply the two recombination frequencies

Question 20

How do you find the expected number of offspring with a double crossover?

Answer 20

total offspring x probability

Question 21

How do you calculate coefficient of coincidence?

Answer 21

observed double crossovers/expected double crossovers

Question 22

How do you calculate interference?

Answer 22

1 - coefficient of coincidence

Question 23

My interference is 0.23. What does this mean

Answer 23

I am observing 77% of double crossovers
I am not observing 23% of double crossovers

Question 24

True or False: if two genes are 51 map units apart on the same chromosome, they are linked

Answer 24

False