ch 6 genetic linkage & mapping in eukaryotes

Question 1

genetic map

Answer 1

(also called chromosome map, genetic linkage map) a diagram that shows the relative locations of genes or other DNA segments on a chromosome

Question 2

synteny

Answer 2

the situation in which two or more genes are located on the same chromosome

Question 3

genetic linkage

Answer 3

the phenomenon in which genes that are close together on the same chromosome tend to be transmitted as a unit

Question 4

linkage groups

Answer 4

a single chromosome, or all of the genes found on a single chromosome, which are linked together; also called a synteny group

Question 5

two-factor cross

Answer 5

a cross in which an experimenter follows the outcome of two different characters

Question 6

three-factor cross

Answer 6

a cross in which the experimenter follows the outcome of three different characters

Question 7

recombinant

Answer 7

1. refers to a cell or offspring that carries a new combination of alleles or traits due to crossing over or due to the independent assortment of chromosomes (also called nonparental)
2. describes DNA molecules that are produced by molecular techniques in which segments of DNA are joined to each other in ways that differ from their original arrangements in their native chromosomal sites (the cloning of DNA into vectors is an example)

Question 8

nonrecombinant

Answer 8

refers to a cell or offspring that carries the same combinations of alleles found in the chromosome of their parents or in the chromosomes of the parental generation in linkage experiments

Question 9

genetic recombination

Answer 9

1. the process in which chromosomes are broken and then rejoined to form a novel genetic recombination
2. the process in which alleles are assorted and passed to offspring in combinations that are different from those found in the parents

Question 10

recombinant offspring

Answer 10

an offspring that has inherited a combination of alleles or a combination of traits that is different from either of their parents. for unlinked genes, recomb offspring are produced via independent assortment for linked genes, recomb offspring are produced by crossing over

Question 11

genetic mapping

Answer 11

any method used to determine the linear order and distance of separation among genes that are linked to each other along the same chromosome; also used to determine the use of genetic crosses to determine the order of linked genes

Question 12

map distance

Answer 12

the relative distance between sites along a simple chromosome; in a testcross, it is defined as the number of recomb offspring divided by the total number of offspring, multiplied by 100

Question 13

map unit (mu)

Answer 13

a unit of map distance obtained from genetic crosses; one map unit is equivalent to 1% recomb offspring in a testcross (the same as a centiMorgan (cM))

Question 14

positive interference

Answer 14

the phenomenon in which a crossover that occurs in one region of a chromosome decreases that probability that another crossover will occur nearby

Question 15

spores

Answer 15

haploid cells that are produced by certain species such as fungi

Question 16

ascus (asci)

Answer 16

a sac that contains haploid spores of fungi

Question 17

parental ditype (PD)

Answer 17

an ascus that contains four spores with the parental combos of alleles

Question 18

tetratype (T)

Answer 18

an ascus that has two spores with the parental combos of alleles and two spores with nonparental combos

Question 19

nonparental ditype (NPD)

Answer 19

an ascus that contains four spores that all have a nonparental combo of alleles

Question 20

mitotic recombination

Answer 20

crossing over that occurs during mitosis and produces a pair of recombinant chromosomes