Linkage and Linked Genes

Question 1

T or F: Genes that are located on the same chromosome are said to be linked.

Answer 1

True

Question 2

T or F: Linkage violates Mendel’s Law of Independent Assortment

Answer 2

True

Question 3

T or F: The further apart two genes are, the more likely it is that a crossover will occur between the genes

Answer 3

True

Question 4

T or F: The closer two genes are, the more likely it is that a crossover will occur between the genes

Answer 4

False

Question 5

Be able to distinguish between parental and recombinant gamete types from diagrams of chromosomes.

Answer 5

o Parental type gametes are those formed without a crossover

o Recombinant types are those formed when a crossover occurs

Question 6

What is a crossover? (Define Crossing Over)

Answer 6

Exchange of genes between nonsister chromatids of homologous chromosomes.
Allows new combinations of genes along the length of a chromosome.
Not as common.
Called recombinant.
More likely if the genes are farther apart.

Question 7

At which stage of meiosis does crossing over occur?

Answer 7

Prophase I of Meiosis I

Question 8

Crossing over is defined as an exchange of arms between (sister or nonsister) chromatids of (homologous or nonhomologous) chromosomes. (pick 1 word in each set of parentheses)

Answer 8

nonsister

homologous

Question 9

What are the units of map distance?

Answer 9

centi-morgans (cM)

Question 10

If an individual of genotype AaBb has one chromosome containing Ab and the other chromosome containing aB and the two genes are 16 cM apart, what proportion of the gametes will be AB?

Answer 10

Mapping distance is 16 cM, so the relative frequencies are 84% parental and 16% recombinant.
Parental gametes: Each is 42% of the total, so
Recombinant gametes are each 8%.