Question 1

Chiasmata can be seen through a light microscope and are sites of recombination.

Accepted Answer

A) True 
 B)False  True

Question 2

A female mouse from a true-breeding wild-type strain was crossed to a male mouse with apricot eyes (ap)and grey body (gy).The F1 mice were wild-type for both traits.When the F1 were interbred,the F2 were distributed as follows (200 total):$$\begin{array} { | l | l | r | } 
\hline \text { Females: } & \text { all wild type } & \
\hline \text { Males: } & \text { wild type } & 91 \
\hline & \text { apricot } & 11 \
\hline & \text { grey } & 9 \
\hline & \text { apricot, grey } & 89 \
\hline
\end{array}$$ 
Explain these results.

Accepted Answer

ap and gy are X-linked and 10 map units apart.

Question 3

Suppose a three-point testcross was conducted involving the genes X,Y,and Z.If the most abundant classes are XYz and xyZ and the rarest classes are xYZ and Xyz,which gene is in the middle?

Accepted Answer

A)  X 
B)  Y 
C)  Z 
D)  cannot be determined 
E)  either Z or Y 
A)  X 
B)  Y 
C)  Z 
D)  cannot be determined 
E)  either Z or Y B

Question 4

Females heterozygous for the recessive second chromosome mutations pn,px,and sp are mated to a male homozygous for all three mutations.The offspring are as follows:$$\begin{array} { | l | r | } 
\hline p x s p c n & 1,461 \
\hline p x s p + & 3,497 \
\hline p x + c n & 1 \
\hline p x + + & 11 \
\hline + s p c n & 9 \
\hline + s p + & 0 \
\hline + + c n & 3,482 \
\hline + + + & \underline { 1,539 } \
\hline & 10,000 \
\hline
\end{array}$$ 
Which method provides more confidence as to the correct order of the genes?

Accepted Answer

The three-point method gives an unambig

Question 5

Three-point crosses are more tedious and less accurate than two-point crosses.

Accepted Answer

A) True 
 B)False

Question 6

Two genes are considered linked when F2 progeny more commonly show the recombinant genotype.

Accepted Answer

A) True 
 B)False

Question 7

Map distances between each pair of three linked genes L,M,and N are measured by two-point test crosses and determined to be: L-M = 20 cM,M-N = 25 cM,and L-N = 38 cM.Explain why the measured distance between the two farthest apart genes is not equal to the sum of the two shorter distances.

Accepted Answer

The two-point cross between L

Question 8

Suppose an individual is heterozygous for a pair of alleles (e.g. ,A/a).Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells homozygous for a? (Pick the most precise answer. )

Accepted Answer

A)  The crossover would have to occur between the A locus and the centromere and involve two homologous (non-sister)chromatids. 
B)  The crossover would have to occur between the A locus and the end of the chromosome and involve two homologous (non-sister)chromatids. 
C)  The crossover would have to occur on the same chromosome arm as the A locus and involve two homologous (non-sister)chromatids. 
D)  The crossover would have to occur on the same chromosome as the A locus and involve two homologous (non-sister)chromatids. 
E)  The crossover would have to occur between the A locus and the centromere and involve two sister chromatids (not homologous)chromatids. 
A)  The crossover would have to occur between the A locus and the centromere and involve two homologous (non-sister)chromatids. 
B)  The crossover would have to occur between the A locus and the end of the chromosome and involve two homologous (non-sister)chromatids. 
C)  The crossover would have to occur on the same chromosome arm as the A locus and involve two homologous (non-sister)chromatids. 
D)  The crossover would have to occur on the same chromosome as the A locus and involve two homologous (non-sister)chromatids. 
E)  The crossover would have to occur between the A locus and the centromere and involve two sister chromatids (not homologous)chromatids.

Question 9

Which of the following is usually true of a chi-square test performed when deciding whether two genes are linked?

Accepted Answer

A)  the p-value is 2 
B)  degrees of freedom (df)= 2 
C)  the minimum sample size is 1000 
D)  the null hypothesis is that the loci are not linked 
E)  degrees of freedom (df)= 4 
A)  the p-value is 2 
B)  degrees of freedom (df)= 2 
C)  the minimum sample size is 1000 
D)  the null hypothesis is that the loci are not linked 
E)  degrees of freedom (df)= 4

Question 10

Genes chained together by linkage relationships are known collectively as a linkage group.

Accepted Answer

A) True 
 B)False

Question 11

In Drosophila,singed bristles (sn)and carnation eyes (car)are both caused by recessive,X-linked alleles.The wild-type alleles (sn+ and car+)are responsible for straight bristles and red eyes,respectively.A sn car female is mated to a sn+ car+ male and the F1 progeny are interbred.The F2 males are distributed as follows.What is the value of ?2 for a test of the hypothesis that the sn and car genes are unlinked? $$\begin{array} { | l | l | } 
\hline s n \text { car } ^ { + } & 55 \
\hline s n \text { car } ^ { + } & 45 \
\hline s n ^ { + } \mathrm { car } ^ { + } & 45 \
\hline \mathrm { sn } ^ { + } \mathrm { car } ^ { + } & 55 \
\hline
\end{array}$$

Accepted Answer

A)  0.5 
B)  1.0 
C)  2.0 
D)  0.4 
E)  20 
A)  0.5 
B)  1.0 
C)  2.0 
D)  0.4 
E)  20

Question 12

In fruit flies,the recessive pr and cn mutations cause brown and bright-red eyes,respectively (wild-type flies have brick-red eyes).The double mutant pr cn combination has orange eyes.A female who has wild-type eyes is crossed to an orange-eyed male.Their progeny have the following distribution of eye colours: $$\begin{array} { | l | r | } 
\hline \text { wild-type } & 8 \
\hline \text { brown } & 241 \
\hline \text { bright-red } & 239 \
\hline \text { orange } & 12 \
\hline & 500 \
\hline
\end{array}$$
What is the genotype of the mother of these progeny?

Accepted Answer

A)  pr cn/pr+ cn+ 
B)  pr+ cn/pr+ cn 
C)  pr+ cn/pr cn+ 
D)  pr cn+/pr cn+ 
E)  pr cn/pr cn 
A)  pr cn/pr+ cn+ 
B)  pr+ cn/pr+ cn 
C)  pr+ cn/pr cn+ 
D)  pr cn+/pr cn+ 
E)  pr cn/pr cn

Question 13

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances.
In a man heterozygous for all six genes,what fraction of his sperm would be recombinant in the a-f interval?

Accepted Answer

The answer of Suppose the map for a particular human...

Question 14

Females heterozygous for the recessive second chromosome mutations pn,px,and sp are mated to a male homozygous for all three mutations.The offspring are as follows:$$\begin{array} { | l | r | } 
\hline p x s p c n & 1,461 \
\hline p x s p + & 3,497 \
\hline p x + c n & 1 \
\hline p x + + & 11 \
\hline + s p c n & 9 \
\hline + s p + & 0 \
\hline + + c n & 3,482 \
\hline + + + & \underline { 1,539 } \
\hline & 10,000 \
\hline
\end{array}$$ 
Using the two-point cross method,what are the distances between these three genes?

Accepted Answer

px-sp = 0.2 m.u. ,p

Question 15

Consider a pair of homologous chromosomes heterozygous for three genes (e.g.ABC/abc)during prophase I of meiosis.Let the sister chromatids of one homolog be numbered 1 and 2;and the sister chromatids of the other homolog be numbered 3 and 4.A crossover that would result in genetic recombination (e.g. ,Abc or aBC)could involve which chromatids?

Accepted Answer

A)  1 & 2 or 3 & 4 
B)  1 & 3 or 2 & 4 
C)  1 & 4 or 2 & 3 
D)  1 & 3 or 1 & 4 or 2 & 3 or 2 & 4 
E)  any two of the four chromatids 
A)  1 & 2 or 3 & 4 
B)  1 & 3 or 2 & 4 
C)  1 & 4 or 2 & 3 
D)  1 & 3 or 1 & 4 or 2 & 3 or 2 & 4 
E)  any two of the four chromatids

Question 16

Recombination frequencies near 50 percent suggest that

Accepted Answer

A)  two genes are on different chromosomes. 
B)  two genes lie very close together on the same chromosome. 
C)  two genes are on the same chromosome but lie very far apart. 
D)  two genes are on different chromosomes,or two genes are on the same chromosome but lie very far apart. 
E)  none of the choices are correct. 
A)  two genes are on different chromosomes. 
B)  two genes lie very close together on the same chromosome. 
C)  two genes are on the same chromosome but lie very far apart. 
D)  two genes are on different chromosomes,or two genes are on the same chromosome but lie very far apart. 
E)  none of the choices are correct.

Question 17

Sturtevant's detailed mapping studies of the X chromosome of Drosophila established what genetic principle?

Accepted Answer

A)  That genes are arranged in a linear order on the chromosomes. 
B)  That genes are carried on chromosomes. 
C)  That sex determination is controlled by the X and Y chromosomes. 
D)  That segregation of an allelic gene pair is accompanied by disjunction of homologous chromosomes. 
E)  That different pairs of chromosomes assort independently. 
A)  That genes are arranged in a linear order on the chromosomes. 
B)  That genes are carried on chromosomes. 
C)  That sex determination is controlled by the X and Y chromosomes. 
D)  That segregation of an allelic gene pair is accompanied by disjunction of homologous chromosomes. 
E)  That different pairs of chromosomes assort independently.

Question 18

Syntenic genes are

Accepted Answer

A)  always recombinant 
B)  always unlinked 
C)  assort independently 
D)  always linked 
E)  located on the same chromosome 
A)  always recombinant 
B)  always unlinked 
C)  assort independently 
D)  always linked 
E)  located on the same chromosome

Question 19

A dihybrid test cross is made between genes H and I.You wish to use the χ2 test to test the hypothesis that the H and I genes are unlinked.How many degrees of freedom would there be in this test?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  0 
A)  1 
B)  2 
C)  3 
D)  4 
E)  0

Question 20

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances.
In a man of the genotype ABCDEF/abcdef,what event would give rise to a sperm with the genotype abcdeF?

Accepted Answer

A crossover between

Chiasmata can be seen through a light microscope and are sites of recombination.

Suppose a three-point testcross was conducted involving the genes X,Y,and Z.If the most abundant classes are XYz and xyZ and the rarest classes are xYZ and Xyz,which gene is in the middle?

Three-point crosses are more tedious and less accurate than two-point crosses.

Two genes are considered linked when F₂ progeny more commonly show the recombinant genotype.

Map distances between each pair of three linked genes L,M,and N are measured by two-point test crosses and determined to be: L-M = 20 cM,M-N = 25 cM,and L-N = 38 cM.Explain why the measured distance between the two farthest apart genes is not equal to the sum of the two shorter distances.

Suppose an individual is heterozygous for a pair of alleles (e.g. ,A/a).Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells homozygous for a? (Pick the most precise answer. )

Which of the following is usually true of a chi-square test performed when deciding whether two genes are linked?

Genes chained together by linkage relationships are known collectively as a linkage group.

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances. In a man heterozygous for all six genes,what fraction of his sperm would be recombinant in the a-f interval?

Recombination frequencies near 50 percent suggest that

Sturtevant's detailed mapping studies of the X chromosome of Drosophila established what genetic principle?

Syntenic genes are

A dihybrid test cross is made between genes H and I.You wish to use the χ² test to test the hypothesis that the H and I genes are unlinked.How many degrees of freedom would there be in this test?

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances. In a man of the genotype ABCDEF/abcdef,what event would give rise to a sperm with the genotype abcdeF?

Mendels Principles of Heredity

Extensions to Mendels Laws

Linkage, Recombination, and the Mapping of Genes on Chromosomes

Dna Structure, Replication, and Recombination

Anatomy and Function of a Gene: Dissection Through Mutation

Gene Expression: the Flow of Information From Dna to Rna to Protein

Digital Analysis of Genomes

Genome Annotation

Analyzing Genomic Variation

The Eukaryotic Chromosome

Chromosomal Rearrangements and Changes in Chromosome Number

Bacterial Genetics

Organellar Inheritance

Gene Regulation in Prokaryotes

Gene Regulation in Eukaryotes

Manipulating the Genomes of Eukaryotes

The Genetic Analysis of Development

The Genetics of Cancer

Variation and Selection in Populations

Genetics of Complex Traits

Exploring Synthetic Biology: Concepts, Techniques, and Applications

Filters

Exam 3: The Chromosome Theory of Inheritance

Chiasmata can be seen through a light microscope and are sites of recombination.

Suppose a three-point testcross was conducted involving the genes X,Y,and Z.If the most abundant classes are XYz and xyZ and the rarest classes are xYZ and Xyz,which gene is in the middle?

Three-point crosses are more tedious and less accurate than two-point crosses.

Two genes are considered linked when F2 progeny more commonly show the recombinant genotype.

Map distances between each pair of three linked genes L,M,and N are measured by two-point test crosses and determined to be: L-M = 20 cM,M-N = 25 cM,and L-N = 38 cM.Explain why the measured distance between the two farthest apart genes is not equal to the sum of the two shorter distances.

Suppose an individual is heterozygous for a pair of alleles (e.g. ,A/a).Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells homozygous for a? (Pick the most precise answer. )

Which of the following is usually true of a chi-square test performed when deciding whether two genes are linked?

Genes chained together by linkage relationships are known collectively as a linkage group.

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances. In a man heterozygous for all six genes,what fraction of his sperm would be recombinant in the a-f interval?

Recombination frequencies near 50 percent suggest that

Sturtevant's detailed mapping studies of the X chromosome of Drosophila established what genetic principle?

Syntenic genes are

A dihybrid test cross is made between genes H and I.You wish to use the χ2 test to test the hypothesis that the H and I genes are unlinked.How many degrees of freedom would there be in this test?

Suppose the map for a particular human chromosome interval is: a-1-b-1-c-1-d-1-e-1-f,where the numbers indicate map distances. In a man of the genotype ABCDEF/abcdef,what event would give rise to a sperm with the genotype abcdeF?

Mendels Principles of Heredity

Extensions to Mendels Laws

Linkage, Recombination, and the Mapping of Genes on Chromosomes

Dna Structure, Replication, and Recombination

Anatomy and Function of a Gene: Dissection Through Mutation

Gene Expression: the Flow of Information From Dna to Rna to Protein

Digital Analysis of Genomes

Genome Annotation

Analyzing Genomic Variation

The Eukaryotic Chromosome

Chromosomal Rearrangements and Changes in Chromosome Number

Bacterial Genetics

Organellar Inheritance

Gene Regulation in Prokaryotes

Gene Regulation in Eukaryotes

Manipulating the Genomes of Eukaryotes

The Genetic Analysis of Development

The Genetics of Cancer

Variation and Selection in Populations

Genetics of Complex Traits

Exploring Synthetic Biology: Concepts, Techniques, and Applications

Filters

Two genes are considered linked when F₂ progeny more commonly show the recombinant genotype.

A dihybrid test cross is made between genes H and I.You wish to use the χ² test to test the hypothesis that the H and I genes are unlinked.How many degrees of freedom would there be in this test?