Chapter Five: Linkage, Recombination, and Gene Mapping Flashcards

1
Q

when genes are inherited together

A

genetic linkage

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2
Q

linked genes may become separated by ___ during ___

A

recombination
meiosis

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3
Q

genes located on the same chromosome

A

syntenic genes

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4
Q

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

A

epistasis or linkage

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5
Q

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

A

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

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6
Q

parental and recombinant configurations are ___ from each other

A

different

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7
Q

autosomal linkage can be detected by ___

A

a testcross

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8
Q

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

A

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

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9
Q

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

A

linkage

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10
Q

Frans Janssens observed ___ between chromosomes during prophase one

A

chiasmata

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11
Q

chiasmata is ___

A

the point of attachment between non sister chromatids of homologs

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12
Q

TH Morgan suggested that chiasmata were sites of ___ and ___

A

breakage and exchange

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13
Q

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

A

reciprocal exchange of chromosomes

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14
Q

alleles used as a point of reference for recombination

A

genetic markers

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15
Q

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

A

nondisjunction

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16
Q

___ help homologs pair but disappear during prophase one

A

synaptonemal complexes

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17
Q

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

A

chiasmata and cohesion

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18
Q

cohesion complex functions to ___

A

connect sister chromatids

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19
Q

percentage of total progeny that were recombinant types

A

recombination frequencies (RF)

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20
Q

RF can be used to measure ___

A

physical distance between two linked genes

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21
Q

1% RF = ___ = ___

A

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

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22
Q

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

23
Q

the RF of unlinked genes is 50% due to ___

A

independent assortment

24
Q

the RF of linked genes cannot exceed ___

25
why can't the RF of linked genes exceed 50%
meiosis without crossovers produce only parental chromosomes single and double crossovers produce a 1:1 parental:recombinant chromosomes ratio on average
26
alleles are sufficiently close together on the same chromosome so that their alleles do not assort independently
linked genes
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
unlinked genes
28
in linked genes, parental ___ recombinant and RF ___ 50%
> (greater than) < (less than)
29
in unlinked genes, parental ___ recombinant and RF ___ 50%
equals equals
30
a genes specific location on a chromosome
locus (plural loci)
31
assign a gene to its locus
gene mapping
32
why is gene mapping important
knowing a gene's locus can be used to isolate DNA and understand gene function
33
it is possible to map genes based on ___
recombination frequencies (distance between genes)
34
limitations of two point crosses
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
35
___ provide faster and more accurate mapping than ___
three point crosses two point crosses
36
comparing pairwise RF's of three genes shows which are ___ and which are ___
furthest apart in the middle
37
genes with a ___ RF will be further apart on the gene map
higher
38
RF numbers might not always add up completely accurate because of ___
interference (less double crossovers than expected)
39
occurrence of crossover in one portion of a chromosome interferes with crossover in an adjacent portion of the chromosome
chromosomal interference
40
genes connected by linkage relationships; when many genes per chromosome have been mapped
linkage groups
41
how to determine if a variation from the expected phenotypic ratio is from epistasis or linkage
chi squared
42
in linkage studies, the null hypothesis is that there are ___
no linkages
43
yeast and bread mold have a ___ state and a ___ state
haploid diploid
44
all four haploid produce of yeast and bread mold meiosis are contained within ___
ascus (sac)
45
can germinate and survive as viable haploids that divide by mitosis
ascospores
46
four ascospores in a single ascus are referred to as
tetrad
47
mitotic recombination occurs because of ___ and can produce ___
mutations genetic mosaics
48
patches of somatic tissue in flies with different phenotypes
twin spots
49
mitotic recombinations have major repercussions to ___
human health
50
portions of a yeast colony with different phenotype than the rest of the colony
sectors
51
___ of sector indicates when recombination took place
proportional size
52
if sector is the entire colony, the recombination took place ___. if sector is a small portion of the colony, the recombination took place ___
in or near the original cell later on in the colony
53
crossing over occurs in ___ ONLY
prophase one