Chapter Five: Linkage, Recombination, and Gene Mapping

Question 1

when genes are inherited together

Answer 1

genetic linkage

Question 2

linked genes may become separated by ___ during ___

Answer 2

recombination
meiosis

Question 3

genes located on the same chromosome

Answer 3

syntenic genes

Question 4

deviation from a typical phenotypic ratio can indicate either ___ or ___

Answer 4

epistasis or linkage

Question 5

when looking at gene linkage in a cross involving X-linked genes, only ___ are considered

Answer 5

male progeny (because they only have one X copy from their mother)

Question 6

parental and recombinant configurations are ___ from each other

Answer 6

different

Question 7

autosomal linkage can be detected by ___

Answer 7

a testcross

Question 8

when looking at gene linkage for an autosomal gene, only ___ are considered

Answer 8

the heterozygote parent (the homozygous parent will give the same alleles whether crossing over occurs or not)

Question 9

the 9:3:3:1 ratio expected for dihybrids is altered with ___

Answer 9

linkage

Question 10

Frans Janssens observed ___ between chromosomes during prophase one

Answer 10

chiasmata

Question 11

chiasmata is ___

Answer 11

the point of attachment between non sister chromatids of homologs

Question 12

TH Morgan suggested that chiasmata were sites of ___ and ___

Answer 12

breakage and exchange

Question 13

H. Creighton and B. McClintock and C. Stern showed direct evidence that genetic recombination depends on the ___

Answer 13

reciprocal exchange of chromosomes

Question 14

alleles used as a point of reference for recombination

Answer 14

genetic markers

Question 15

if recombination did not occur, ___ during meiosis one would happen frequently

Answer 15

nondisjunction

Question 16

___ help homologs pair but disappear during prophase one

Answer 16

synaptonemal complexes

Question 17

during prophase one, chromosomes are still attached with ___ and ___

Answer 17

chiasmata and cohesion

Question 18

cohesion complex functions to ___

Answer 18

connect sister chromatids

Question 19

percentage of total progeny that were recombinant types

Answer 19

recombination frequencies (RF)

Question 20

RF can be used to measure ___

Answer 20

physical distance between two linked genes

Question 21

1% RF = ___ = ___

Answer 21

1 map unit (m.u.)
1 centiMorgan (cM)

Question 22

recombinant gametes are ___ frequent than parental gametes when genes are linked

Answer 22

less

Question 23

the RF of unlinked genes is 50% due to ___

Answer 23

independent assortment

Question 24

the RF of linked genes cannot exceed ___

Answer 24

50%

Question 25

why can’t the RF of linked genes exceed 50%

Answer 25

meiosis without crossovers produce only parental chromosomes
single and double crossovers produce a 1:1 parental:recombinant chromosomes ratio on average

Question 26

alleles are sufficiently close together on the same chromosome so that their alleles do not assort independently

Answer 26

linked genes

Question 27

genes are either on two different chromosomes or are sufficiently far apart on the same chromosome that at least one crossover occurs between them in every meiosis

Answer 27

unlinked genes

Question 28

in linked genes, parental ___ recombinant and RF ___ 50%

Answer 28

> (greater than)
< (less than)

Question 29

in unlinked genes, parental ___ recombinant and RF ___ 50%

Answer 29

equals
equals

Question 30

a genes specific location on a chromosome

Answer 30

locus (plural loci)

Question 31

assign a gene to its locus

Answer 31

gene mapping

Question 32

why is gene mapping important

Answer 32

knowing a gene’s locus can be used to isolate DNA and understand gene function

Question 33

it is possible to map genes based on ___

Answer 33

recombination frequencies (distance between genes)

Question 34

limitations of two point crosses

Answer 34

difficult to determine gene order if two genes are close together
actual distances between genes don’t always add up
pairwise crosses are time and labor consuming

Question 35

___ provide faster and more accurate mapping than ___

Answer 35

three point crosses
two point crosses

Question 36

comparing pairwise RF’s of three genes shows which are ___ and which are ___

Answer 36

furthest apart
in the middle

Question 37

genes with a ___ RF will be further apart on the gene map

Answer 37

higher

Question 38

RF numbers might not always add up completely accurate because of ___

Answer 38

interference (less double crossovers than expected)

Question 39

occurrence of crossover in one portion of a chromosome interferes with crossover in an adjacent portion of the chromosome

Answer 39

chromosomal interference

Question 40

genes connected by linkage relationships; when many genes per chromosome have been mapped

Answer 40

linkage groups

Question 41

how to determine if a variation from the expected phenotypic ratio is from epistasis or linkage

Answer 41

chi squared

Question 42

in linkage studies, the null hypothesis is that there are ___

Answer 42

no linkages

Question 43

yeast and bread mold have a ___ state and a ___ state

Answer 43

haploid
diploid

Question 44

all four haploid produce of yeast and bread mold meiosis are contained within ___

Answer 44

ascus (sac)

Question 45

can germinate and survive as viable haploids that divide by mitosis

Answer 45

ascospores

Question 46

four ascospores in a single ascus are referred to as

Answer 46

tetrad

Question 47

mitotic recombination occurs because of ___ and can produce ___

Answer 47

mutations
genetic mosaics

Question 48

patches of somatic tissue in flies with different phenotypes

Answer 48

twin spots

Question 49

mitotic recombinations have major repercussions to ___

Answer 49

human health

Question 50

portions of a yeast colony with different phenotype than the rest of the colony

Answer 50

sectors

Question 51

___ of sector indicates when recombination took place

Answer 51

proportional size

Question 52

if sector is the entire colony, the recombination took place ___. if sector is a small portion of the colony, the recombination took place ___

Answer 52

in or near the original cell
later on in the colony

Question 53

crossing over occurs in ___ ONLY

Answer 53

prophase one