Ch. 5 Linkage, Recombination, and Eukaryotic Gene Mapping

Question 1

What are linked genes

Answer 1

Genes located to close together on the same chromosome

Question 2

What would be the ratio of a dihybrid cross without linked genes

Answer 2

9:3:3:1

Question 3

How are crosses with linkage notated

Answer 3

A. B. a. b. A. B
—————. X. —————. =. ————
A. B a. b a. b
Correct form

Never
A. a. A. B
————. ————-
B. b. b. a

First never
Two alleles are always located on on different homologous chromosome

Second never
Keep same other of alleles on both sides or it implies they are allelic

Question 4

What kind of progeny are expected with complete linkage

Answer 4

Non-recombinant

Question 5

What is nonrecombinant gametes

Answer 5

Gametes that contain only original combinations of alleles present on the parents

Question 6

What is recombinant gametes

Answer 6

Gametes with new combinations of alleles

Question 7

What phase does crossing over take place

Answer 7

Late prophase 1

Question 8

For one crossover event, why is the frequency of recombinant 50%

Answer 8

Crossover takes place between only two of the four chromatids of a homologous pair

Question 9

What is the equation for recombination frequency

Answer 9

Number of recombinant progeny
——————————————— x100%
Total number of progeny

Question 10

What does the different notations look like for coupling and repulsion of the gametes p+b+ p b

Answer 10

Coupling

p+ b+
—————
p. b

Repulsion

p+. b
—————
p. b+

Question 11

What is a genetic map

Answer 11

Chromosome map calculated by using the genetic phenomenon of recommendation

Question 12

What is a physical map

Answer 12

Chromosome map calculated by using physical distances along the chromosome

Question 13

Map units

Answer 13

Distances measured on a map (m.u)

1 map distance= 1% recombination

Also called centiMorgans (cM)

Question 14

When making a genetic map what does a 50% recommendation frequency mean

Answer 14

That the alleles are except with independent assortment. Therefore they are either on differ t chromosome or very far apart on the same chromosome

Question 15

The degree to which one crossover interferes with additional crossover in the same region is called

Answer 15

Interference

Question 16

How does you calcite interference

Answer 16

First coefficient of coincidence

#of observed double crossovers
———————————————
# of excepted double crossovers 

Second interference

1-coefficient of coincidence