Linkage, chromosome exchange, and mapping

Question 1

Genetic Linkage

Answer 1

Alleles of genes close together on the same chromosome travel together more often than not

Question 2

Genetic Linkage

Are there more parental or recombinant?

Answer 2

Parental combinations > recombinant combinations

Question 3

Linkage is defined as —- recombination

Answer 3

<50% recombination

Question 4

Independent assortment

Answer 4

50% recombination

Question 5

Syntenic genes

Answer 5

Genes that lie on the same chromosome

Question 6

What is the max recombination for syntenic genes?

Answer 6

50%

Question 7

What are recombinant frequencies used for?

Answer 7

To map the position of genes relative to one another on chromosomes in two and three factor crosses

Question 8

What is more rapid and accurate than two-point mapping?

Answer 8

Three factor crosses

Question 9

What occurs when fewer double cross-overs occur than would be expected by chance

Answer 9

Interference

Question 10

The greater the physical distance between linked genes…

Answer 10

the higher the recombination frequency

Question 11

The _____ the distance between gene pairs, the more accurate/useful the map is to predict ________

Answer 11

closer, inheritance

Question 12

Chi-square test

Answer 12

Determines whether deviations from independent assortment ratios are due to chance

Question 13

P-value

Answer 13

measures the likelihood that a set of data support a null hypothesis of no linkage

Question 14

How can genetic markers refine how well we can estimate the probability of inheriting a disease allele

Answer 14

The closer the distance between gene pairs, the more accurate

Question 15

How do alleles on the same chromosome become separated?

Answer 15

Recombination

Question 16

Extend Mendel’s Observations

Genes had one dominant and one recessive allele

Answer 16

Multiple alleles and many kinds of dominant alleles and dominance relationships are possible

Question 17

Extend Mendel’s Observations

Genes control one trait

Answer 17

Genes can affect many traits (pleiotropy)

Question 18

Pleiotropy

Answer 18

One gene influences many traits

Question 19

Multifactorial (polygenic)

Answer 19

a single component of the phenotype can be controlled by several independent gene loci.

Question 20

Epistasis

Answer 20

the expression of one gene is affected by the expression of one or more independently inherited genes.

Question 21

Complementary action

Answer 21

when two different genes work together to contribute to one single trait

Question 22

Redundancy

Answer 22

two or more genes are performing the same function and that inactivation of one of these genes has little or no effect on the biological phenotype

Question 23

Penetrance

Answer 23

the proportion of individuals in a population who carry a specific gene and express the related trait.

Question 24

Gene symbols for linkage:
Linked
Unlinked
Unsure

Answer 24

Linked = /

Unlinked = ;

Unsure = dot

Question 25

Linkage phase

Answer 25

the arrangement of alleles on the two chromosomes

Question 26

How to test for linkage between two genes in a diploid organism?

Answer 26

F1 must be heterozygous
F1 will be either parental or recombinant
Use test cross to determine genotypes of F1 gametes

Question 27

RF%

Answer 27

RF%=recombinants/total

Question 28

What provides a gene better chance of crossover in meiosis?

Answer 28

Greater distance b/w linked genes

Question 29

RF is equal to

Answer 29

a genetic map unit (m.u.) centimorgan (cM)

Question 30

Gene locus

Answer 30

place on the map where the gene is located

Question 31

Who discovered mapping?

Answer 31

Alfred Sturtevant

Question 32

Two-point cross

Answer 32

Testing the RF b/w two genes

Question 33

Do double crossovers increase the frequency of recombinants between distant genes?

Answer 33

NO

Still never greater than 50%

Question 34

Three-point cross

Answer 34

Testing the RF b/w three genes

Question 35

What two things does a three-point testcross reveal?

Answer 35

1. Gene order

2. Relative distance of all three genes

Question 36

Why do the smaller distances not add up to the larger distance?

Answer 36

Double cross overs are often less frequent than expected due to chromosomal interference

Question 37

Chiasmata

Answer 37

Point of contact b/w two homologous chromosomes