Lecture 13 Gene Mapping

Question 1

What does the gene map show

Answer 1

• Shows the relative order of genes on the chromosomes

- Shows the distancce between the genes

Question 2

What does a physical gene map show

Answer 2

The actual distances between genes or DNA markers based on direct measurement of the DNA

Question 3

What are cytogenetic maps

Answer 3

Indicate gene positions with respect to cytogenetic markers.

Question 4

What is a linkage map

Answer 4

Shows the relative positions of genes or markers on a chromosome based on meiotic recombination frequencies. Recombination frequency is used to calculate genetic distance

Question 5

What are the uses of Gene maps

Answer 5

1) Identifies genes responsible for diseases or traits (positional cloning)
2) helps you to compare genome organization between organisms
3) effectively combine traits of economic importance in plant or animal breeding.
4) helps the design or analysis of experiments aied at studying gene function.

Question 6

What do the recombination frequencies tell you

Answer 6

50% recombination frequency means that the genes are on different chromosomes or that the genes are far apart on the same chromosome.

Question 7

50 percent recombination tells you what…

Answer 7

The genes are either on two different chromosomes or far apart on the same chromosomes.

Question 8

Less than 50 percent recombination tells you

Answer 8

Genes are linked on the same chromosome.

The smaller the recombination frequency, the closer the two gene loci lie on the chromosome.

Question 9

How do we calculate the genetic distance

Answer 9

The recombination frequency indicates how close two genes lie. The smaller the recombination of frequency, the closer the two gene loci lie on the chromosome.

Question 10

Give the equation used to calculate genetic distance

Answer 10

Recombination frequency = Number of recombinant progeny / Total number of progeny x 100

Question 11

State the units for genetic distance

Answer 11

CM (Centimorgans)

Question 12

10 percent recombination frequency is equal to…

Answer 12

10 Centimorgans of genetic distance

Question 13

Explain what is meant by the term Genetic linkage

Answer 13

Genes that typically stay together during recombination are said to be linked. Two genes that are close together are less likely to become separated than two genes far apart

Question 14

Define linked genes

Answer 14

Two genes that tend to be inherited together and do not separate during crossing over in prophase I of meiosis.
Linked genes are not free to undergo independent assortment.

Question 15

The following statement is True or False… Linked genes are not free to undergo independent assortment

Answer 15

True. The chomosome not the gene is the unit of transmission during meiosis. Linked genes occur on the same chromosome. Chromosomes assort, not genes.

Question 16

What is Giesma

Answer 16

This is a stain used to stain chromosomes.

Question 17

What is G banding

Answer 17

This is the pattern observed when human chromosomes are died with a stain known as Giesma. The Giesma die distinguishes one chromosome region from another.

Question 18

Define cytogenetic map

Answer 18

A cytogenetic map is the visual appearance of a chromosome when stained and viewed under the microscope.

Question 19

What is the p arm

Answer 19

The smaller petit arm/shorter chromosome arm

Question 20

What is the q arm

Answer 20

The longer arm of the chromosome

Question 21

Decode this naming system with respect to a human karyotype 7q31.2

Answer 21

7 = human chromosome number 7 
q = longer q arm
3 = region 3
1 = band 1 
2 = sub band 2

Question 22

Define Haplotype

Answer 22

Set of DNA variations or polymorphisms that tend to be inherited together. A haplotype can refer to a combination of alleles, or to a set of SNPs.