Linkage Questions
Chapter 6
Questions 1
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Genetic recombination occurs during crossing over in
Meiosis I. When two homologous chromosomes form
chiasma genes from a paternal chromosome ay cross
over to the maternal chromosome
This involves physical breaking and recombination of
two chromosomes
Recombination leads to new combinations of genes
that will be included in gametes
The increase in genetic variability insures the ability
of organisms to adjust to the environment and
thereby offers a better possibility of survival of the
species.
Question1 ( con)
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The increase in genetic variability insures the ability
of organisms to adjust to the environment and
thereby offers a better possibility of survival of the
species.
This is reshuffling of the genes resulting in new
combinations
Question 2
The cytological evidence for crossing
over is the presence of synaptinemal
complexes
 These are chromosomes connected by
chiasma undergoing cross overs
 Cross overs involves only two of the
four sister chromatids
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Questions 3
More crossing over occurs between
more distantly related genes
 Two genes that are at a distant have
space for their chromosome arms to
cross and thereby insure the possibility
of genetic exchange between
homologous chromosomes
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Question 5
Double cross overs are expected in
lower frequencies because
 Two genes must be exchanged
simultaneously
 Cross over events on one chromosome
inhibit the cross over events on another
chromosome
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Question 8
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dp---------------------cl--------ap
Question 9
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a + b are on separate chromosomes – random
assortment takes place and the gametes are formed
by independent assortment and segregation
a+ b are linked and far apart so that crossing over
occurs 100% and therefore appears to be like a
a + b are linked so that there is no space for the
exchange to occur
A+ b are on the same chromosome about 10 map units
apart. They have a total of 10 % crossing over
between these two physical points on the chromosome
Question 10
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Colored green
88
Colored yellow
12
Colorless green
8
Colorless yellow 92
Total = 200
Cross overs = 20
20/200 = 10% or 10 map units between the coat color
gene and the plant color gene
Question 13
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Order of the genes
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d---b---pr---vg---c---adp
31
48
54
67
75
83
Question 15
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Order of the genes
sc---------v----s
33
10