Linkage, Recombination And Eukaryotic Mapping

Question 1

What happens during recombination?

Answer 1

Alleles sort into new combinations.

Question 2

What is the principle of segrgation?

Answer 2

Alleles separate during meiosis.

Question 3

What is the principle of independent assortment?

Answer 3

Alleles at one locus sort independently from alleles at another locus.

Question 4

Linked genes segregate together and crossing over produces ___ between them.

Answer 4

Linked genes segregate together and crossing over produces RECOMBINATION between them.

Question 5

What does complete linkage lead to?

Answer 5

Nonrecombinant gametes and nonrecombinant progeny.

Question 6

What does crossing over with linked genes lead to?

Answer 6

Recombinant gametes and recombinant progeny.

Question 7

Becaue genes are carried on chromosomes, this creates a physical connection between genes that are close together on a chromosome. What is the term for this phenomenon?

Answer 7

Linkage.

It can be used to create a genetic map of gene position on chromosomes.

Question 8

What is linkage disequilibirum?

Answer 8

The non-random association of alleles at different loci, which can be the result of close location of genes on a chromosome.

Question 9

What is linkage disequilibrium influenced by?

Answer 9

Selection

The rate the recombination

The rate of mutation

Genetic drift

System of mating

Population structure

Genetic linkage.

Question 10

For single crossovers, the frequency of recombinant gametes is half the frequency of crossing over because:

Answer 10

Each crossover takes place between only two of the four chromatids of a homologous pair.

Question 11

How is recombination frequency calculated?

Answer 11

Recombination frequency = (# recombinant progeny/total # of progeny) x 100%

Question 12

What occurs during coupling?

Answer 12

Wild type alleles are found on one chromosome; mutant alleles are found on the other chromosome.

Question 13

True or false: linked genes segregate together.

Answer 13

True

Question 14

What occurs during coupling?

Answer 14

One chromosome contains both wild-type alleles, one chromosome contains both mutant alleles.

Question 15

What occurs during repulsion?

Answer 15

Wild type alleles and mutant alleles are found on the same chromosome.

Question 16

What does recombination frequency allow us to do?

Answer 16

Recombination frequency allows us to predict expected offspring for a cross with linked genes.

Question 17

The following testcross produces the progeny shown: AaBb x aabb -> 10 AaBb, 40 aaBb, 40 aaBb, 10 aabb. What is the percent recombination betwen the A and B loci? Were the genes in AaBb parent in coupleing or repulsion?

Answer 17

Percent recombination 20%; genes in AaBb parent is in repulsion.

Question 18

What are genetics maps determined by?

Answer 18

Recombinant frequency.

Question 19

A two-strand double crossover between two linked genes produces only what?

Answer 19

Nonrecombinant gametes.

Question 20

How does a single crossover affect chromosomes?

Answer 20

It switches the alleles on homologous chromosomes.

A second crossover will reverse the effects of the first, restoring the original parental combination of alleles and producing only nonrecombinant genotypes in the gametes, althought parts on the chromosomes have recombined.

Question 21

Recombinant chromosomes resulting from the double crossover have only the ___ gene altered.

Answer 21

Middle

Question 22

A three-point testcross is carried out between three linked genes. The resulting nonrecombinant progeny are s+r+c+ and src, and the double cross over progen are s r c+ and s+r+c. Which is the middle locus?

Answer 22

C

Question 23

What is the coefficient of coincidence?

Answer 23

The number of observed double cross/number of expected double crossovers.

Question 24

What is interference?

Answer 24

1n - coefficient of coincidence.

Question 25

What is a restriction enzyme?

Answer 25

An enzyme produced chiefly by certain bacteria, having the property of cleaving DNA molecules at or near a specific sequence of bases.

Question 26

What is RFLP mapping?

Answer 26

A technique in which DNA restriction fragment length polymorphisms are used as reference markers for mappin in relation to known genes or other RFLP loci.

Question 27

What is the genome-wide association study?

Answer 27

A comparison of DNA markers across the genome in people with a disease or trait to people without the disease or trait.

These studies help to identify loci that may be contributing to the trait.

Question 28

True or false: linked genes do not assort independently.

Answer 28

True