BIO 235 Exam 2 Questions and
Answers 100% Pass
Independent assortment - ✔✔Genes assort independently of each other
when they are on opposite chromosomes
Linkage - ✔✔Two genes on a single pair of homologs; exchange occurs
between two non-sister chromatids
Chiasmata - ✔✔Location of exchange of information between chromatids
when does crossing over occur? - ✔✔prophase I of meiosis
How often does recombination occur? - ✔✔Very frequently
What determines how often genes will cross over? - ✔✔Their distance from
one another. The closer they are, the less likely they are to cross over.
1
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,What does it mean when genes are linked? - ✔✔they are on the same
chromosome; assort independently
Describe how geneticists detect linkage of a gene - ✔✔1. Select true-
breeding lines that are homozygous dominant for one trait & homozygous
recessive for the other trait (ygr ANL / ygr ANL & YGR anl / YGR anl).
Parents produce dihybrid F1 population (ygr ANL / YGR anl)
2. Cross the F1 dihybrid with a homozygous recessive (ygr anl / ygr anl).
This will result in an F2 pop. where the dihybrid traits segregate.
3. Cross each F2 individual with a homozygous recessive
How do you determine if the genes are linked or not after performing a test
cross? - ✔✔If the ratio is 1:1:1:1, they assort independently and are
unlinked
If the ratio for the recombinant class is less than the parental class, you
know they do not assort independently and are linked
Parental class - ✔✔original arrangement of alleles on the two chromosomes
(no recombination); came from meiosis unchanged
2
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, Recombinant class - ✔✔does not have chromosomes passed from parents
How is distance between genes found? - ✔✔The farther apart two genes
are located on a chromosome, the higher the probability that a recombinant
event takes place between them
Recombinant frequency (RF) - ✔✔percentage of the total progeny that are
recombinant type
6% RF = ___________ - ✔✔6 map units OR 6 centimorgans
From a test cross, you observe that there are 350 offspring for each parental
genotype and 150 for each recombinant genotype. What is the distance of
the recombinant genes? - ✔✔30 map units
What is one problem with relying on RF in linkage mapping? - ✔✔Genetic
distance is massively underestimated when genes are father apart
Genetic distances are not additive - RF will never be >50%
The farther apart they are, the less reliable the numbers are
Double-crossover is more likely the further they are from each other
3
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Answers 100% Pass
Independent assortment - ✔✔Genes assort independently of each other
when they are on opposite chromosomes
Linkage - ✔✔Two genes on a single pair of homologs; exchange occurs
between two non-sister chromatids
Chiasmata - ✔✔Location of exchange of information between chromatids
when does crossing over occur? - ✔✔prophase I of meiosis
How often does recombination occur? - ✔✔Very frequently
What determines how often genes will cross over? - ✔✔Their distance from
one another. The closer they are, the less likely they are to cross over.
1
100% Pass Guarantee Katelyn Whitman, All Rights
,What does it mean when genes are linked? - ✔✔they are on the same
chromosome; assort independently
Describe how geneticists detect linkage of a gene - ✔✔1. Select true-
breeding lines that are homozygous dominant for one trait & homozygous
recessive for the other trait (ygr ANL / ygr ANL & YGR anl / YGR anl).
Parents produce dihybrid F1 population (ygr ANL / YGR anl)
2. Cross the F1 dihybrid with a homozygous recessive (ygr anl / ygr anl).
This will result in an F2 pop. where the dihybrid traits segregate.
3. Cross each F2 individual with a homozygous recessive
How do you determine if the genes are linked or not after performing a test
cross? - ✔✔If the ratio is 1:1:1:1, they assort independently and are
unlinked
If the ratio for the recombinant class is less than the parental class, you
know they do not assort independently and are linked
Parental class - ✔✔original arrangement of alleles on the two chromosomes
(no recombination); came from meiosis unchanged
2
100% Pass Guarantee Katelyn Whitman, All Rights
, Recombinant class - ✔✔does not have chromosomes passed from parents
How is distance between genes found? - ✔✔The farther apart two genes
are located on a chromosome, the higher the probability that a recombinant
event takes place between them
Recombinant frequency (RF) - ✔✔percentage of the total progeny that are
recombinant type
6% RF = ___________ - ✔✔6 map units OR 6 centimorgans
From a test cross, you observe that there are 350 offspring for each parental
genotype and 150 for each recombinant genotype. What is the distance of
the recombinant genes? - ✔✔30 map units
What is one problem with relying on RF in linkage mapping? - ✔✔Genetic
distance is massively underestimated when genes are father apart
Genetic distances are not additive - RF will never be >50%
The farther apart they are, the less reliable the numbers are
Double-crossover is more likely the further they are from each other
3
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