Question 1

Recombination frequency differs between males and females. Which sex has a higher rate of recombination, heterogametic (males) or homogametic (females)?

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Question 2

The pedigrees below are for a dominant disease where individuals with the dominant disease allele (D) are affec Individuals that were alive were also screened for a polymorphic DNA marker that has six alleles identified as P P4, P5, and P6.
a) In Family B, explain why the P1 marker cannot be assumed to be transmitted with the dominant allele given there is no haplotype data for the first generation.
b) In Family A, how does the information regarding the haplotype of individuals in the first generation allow y determine the allelic phase of the disease?
"Use Figure 5.15 in Chapter 5, page 169 from main title."

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Question 3

What is the Lod score?

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Question 4

A chromosome with a different combination of alleles than parental that is created by crossing over between homologous chromosomes is termed _______.

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Question 5

What would a Lod score of 3.2 tell you about genetic linkage? What information does the 0 value tell you?

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Question 6

In most tests of genetic linkage, the number of double crossovers is LESS than the number expected due to what effect, which limits the number of crossovers that can occur in a short length of chromosome?

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Question 7

A geneticist is mapping the chromosomes of a new fish species. These fish have genes for the dominant traits non- bioluminescent (B), ventral eyes (D), and short spikes (L) with corresponding recessive traits bioluminescent (b), dorsal eyes (d), and long spikes (l). He test- crosses one of these fish who is dominant at all th loci to determine if the three genes are linked resulting in the data shown below: $\frac{(345-125)^{2}}{125}+\frac{(355-215)^{2}}{125}+\frac{(42-125)^{2}}{125}+\frac{(38-125)^{2}}{125}+\frac{(105-125)^{2}}{125}$
$+\frac{(95-125)^{2}}{125}+\frac{(9-125)^{2}}{125}+\frac{(11-125)^{2}}{125}=1148$
 a) Why are these data consistent with genetic linkage among the three genes?
b) Perform a chi- square test to determine if these data show significant deviation from the expected phenotype distribution.
c) Determine the recombination frequencies between each pair of genes.
d) Determine the coefficient of coincidence (COC) and interference (I) values for this data set.

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Question 8

The specific array of alleles making up a set of linked genes on a single chromosome is called a_______ .

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Question 9

Alleles of linked genes usually segregate together during meiosis. When they don't, it is because__________ has occurred between them.

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Question 10

What is the relationship between linked genes and syntenic genes? Are syntenic genes always linked?Are linked genes always syntenic? Describe what is meant by each term.

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Question 11

If there is a maximum Lod score of 4.2 at 0 = 0.31, what can you say about the linkage and the distance between two genes?

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Question 12

Instead of creating a gene map along a chromosome,________ is a method of analysis that detects and locates the genes that, as a group, influence form or appearance.

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Question 13

A geneticist is mapping the chromosomes of the newly captured gremlin. Stripe is heterozy for three linked genes with alleles Ee, Hh, and Bb, that determine if gremlins are evil (E), ha (H), and biting teeth (B). In order to determine if the three genes are linked, a standard testc was done, and the 1000 offspring had the following genotypes: $\begin{array}{ll}
48 & \text { ee Hh bb } \
36 & \text { eehh Bb } \
400 & \text { ee Hh Bb } \
4 & \text { Ee Hh Bb } \
426 & \text { Eehh bb } \
46 & \text { Eehh Bb } \
38 & \text { Ee Hh bb } \
2 & \text { eehh bb }
\end{array}$ Diagram the alleles on the homologous chromosomes of the heterozygous individuals with correct gene order.

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Question 14

5% recombination is equal to ______map unit(s) (m.u.) or centimorgan(s) (cM) of distance between linked genes.

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Question 15

If too little time has passed for crossing over to randomize haplotypes or if natural selection favors certain haplotypes, what would you expect to see?

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Question 16

When constructing a genetic map of Zea mays, Creighton and McClintock used genetic markers as well as structural differences in the homologous copies of chromosome 9 that can be seen under the microscope. What are these structural differences called?

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Question 17

How is Newton Morton's statistical method (Lod score analysis) helpful for calculating the overall probability of genetic linkage when allelic phase is unknown?

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Question 18

Compare and contrast the following three DNA genetic markers: variable number tandem repeats (VNTRs), single nucleotide polymorphisms (SNPs), and restriction fragment length polymorphisms (RFLPs).

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Question 19

Genes A, B, and C lie at map positions 2.5, 7.5, and 17.5, respectively. In a three- point test cross, you observed 2 double crossovers in a total of 1000 progeny. What is the interference in this region?

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Question 20

Refer to this map to answer the questions:
  a) What is the distance between gene E and gene F?
b) Assuming I = 0, what is the probability of no crossovers between gene D and gene E?
c) Assuming I = 0, what is the probability of no crossovers between gene E and gene F?
d) Considering both gene pairs, what is the proportion of nonrecombinant gametes?
e) What is the predicted frequency of each parental gamete (DEF/def )?
f) What is the recombination frequency between gene D and gene E?
g) What is the recombination frequency between gene E and gene F?
h) What is the frequency of two single recombinant gametes between genes D and E?
i) What is the frequency of two single recombinant gametes between genes E and F?
j) What is the frequency of each of the double- recombinant gametes, DeF and dEf?
k) Fill in the blanks below to prove that the sum of the frequencies of the eight predicted gamete genotypes is e 1.0:
 $$\overline { D E F } ^ { + } + \frac { } { d e f } + \frac { } { D e f } +\frac { } { d E F } +\frac { } { D E f } + \frac { }{ d e F } +\frac { } { D e F } + \frac { } { d E f } = 1$$

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Quiz 5: Genetic Linkage and Mapping in Eukaryotes