Question 1

In Drosophila,assume that the gene for scute bristles (s)is located at map position 0.0 and that the gene for ruby eyes (r)is at position 15.0.Both genes are located on the X chromosome and are recessive to their wild-type alleles.A cross is made between scute-bristled females and ruby-eyed males.Phenotypically wild-type F₁ females were then mated to homozygous double mutant males,and 1000 offspring were produced.Give the phenotypes and frequencies expected.

Accepted Answer

The answer of In Drosophila,assume that the gene for scute...

Question 2

When two genes fail to assort independently,the term normally applied is ________.

Accepted Answer

A) discontinuous inheritance 
B) Mendelian inheritance 
C) linkage 
D) tetrad analysis 
E) dominance and/or recessiveness

Question 3

Describe a convenient method for determining gene order from three-point cross results.

Accepted Answer

The answer of Describe a convenient method for determining gene...

Question 4

(a)In a three-point mapping experiment,which three general classes of offspring are expected (assuming crossovers occur)? (b)How many different genotypic classes are expected?

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The answer of (a)In a three-point mapping experiment,which three general...

Question 5

What is the expected evolutionary significance of genetic recombination?

Accepted Answer

The answer of What is the expected evolutionary significance of...

Question 6

Phenotypically wild-type F₁ female Drosophila,whose mothers had light eyes (lt)and fathers had straw (stw)bristles,produced the following offspring when crossed to homozygous light-straw males: $\begin{array}{lc} \text { Phenotype } & \text { Number } \ \hline \text { light-straw } & 22 \ \text { wild-type } & 18 \ \text { light } & 990 \ \text { straw } & \underline{970} \ & \text { Total: } \underline{2000} \end{array}$ Compute the map distance between the light and straw loci.

Accepted Answer

The answer of Phenotypically wild-type F₁ female Drosophila,whose mothers had...

Question 7

Two lines of work indicated that crossing over actually involves breakage and reunion of chromatid material.What organisms were involved,and who did the work?

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The answer of Two lines of work indicated that crossing...

Question 8

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that the recombinant progeny are gE/ge and Ge/ge.

Accepted Answer

A) True 
 B)False

Question 9

What advantage does BrdU (bromodeoxyuridine)have in the study of chromosome structure and recombination?

Accepted Answer

The answer of What advantage does BrdU (bromodeoxyuridine)have in the...

Question 10

Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb,48 Aabb,52 aaBb,94 aabb.These results are consistent with ________.

Accepted Answer

A) sex-linked inheritance with 30% crossing over 
B) linkage with 50% crossing over 
C) linkage with approximately 33 map units between the two gene loci 
D) independent assortment 
E) 100% recombination

Question 11

Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism.If you examined 200 primary oocytes,in how many would you expect to see a chiasma between the two loci?

Accepted Answer

The answer of Assume that there are 12 map units...

Question 12

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that there are 20 map units between the G and E loci.

Accepted Answer

A) True 
 B)False

Question 13

The genes for mahogany eyes and ebony body are approximately 25 map units apart on chromosome III in Drosophila.Assume that a mahogany-eyed female was mated to an ebony-bodied male and that the resulting F₁phenotypically wild-type females were mated to mahogany,ebony males.Of 1000 offspring,what would be the expected phenotypes,and in what numbers would they be expected?

Accepted Answer

The answer of The genes for mahogany eyes and ebony...

Question 14

What are two commonly used DNA landmarks for mapping human genes?

Accepted Answer

The answer of What are two commonly used DNA landmarks...

Question 15

Sister chromatid exchanges increase in frequency in the presence of X rays,certain viruses,ultraviolet light,and certain chemical mutagens.In what autosomal recessive disorder is there known to be an increase in sister chromatid exchanges?

Accepted Answer

The answer of Sister chromatid exchanges increase in frequency in...

Question 16

Provide a brief definition for positive interference.

Accepted Answer

The answer of Provide a brief definition for positive interference....

Question 17

Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb,Aabb,aaBb,aabb.These results are consistent with ________.

Accepted Answer

A) independent assortment 
B) alternation of generations 
C) complete linkage 
D) incomplete dominance 
E) hemizygosity

Question 18

Positive interference occurs when a crossover in one region of a chromosome reduces crossovers in nearby regions.

Accepted Answer

A) True 
 B)False

Question 19

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that the G and E loci assort independently.

Accepted Answer

A) True 
 B)False

Exam 7: Linkage and Chromosome Mapping in Eukaryotes

When two genes fail to assort independently,the term normally applied is ________.

Describe a convenient method for determining gene order from three-point cross results.

(a)In a three-point mapping experiment,which three general classes of offspring are expected (assuming crossovers occur)? (b)How many different genotypic classes are expected?

What is the expected evolutionary significance of genetic recombination?

Two lines of work indicated that crossing over actually involves breakage and reunion of chromatid material.What organisms were involved,and who did the work?

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that the recombinant progeny are gE/ge and Ge/ge.

What advantage does BrdU (bromodeoxyuridine)have in the study of chromosome structure and recombination?

Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb,48 Aabb,52 aaBb,94 aabb.These results are consistent with ________.

Assume that there are 12 map units between two loci in the mouse and that you are able to microscopically observe meiotic chromosomes in this organism.If you examined 200 primary oocytes,in how many would you expect to see a chiasma between the two loci?

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that there are 20 map units between the G and E loci.

What are two commonly used DNA landmarks for mapping human genes?

Sister chromatid exchanges increase in frequency in the presence of X rays,certain viruses,ultraviolet light,and certain chemical mutagens.In what autosomal recessive disorder is there known to be an increase in sister chromatid exchanges?

Provide a brief definition for positive interference.

Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb,Aabb,aaBb,aabb.These results are consistent with ________.

Positive interference occurs when a crossover in one region of a chromosome reduces crossovers in nearby regions.

The cross GE/ge X ge/ge produces the following progeny: GE/ge 404,ge/ge 396,gE/ge 97,Ge/ge 103.From these data,one can conclude that the G and E loci assort independently.