Question 1

Testcrosses may be used by geneticists to determine if two genes are linked.

Accepted Answer

A) True 
 B)False  True

Question 2

What are the forms of crossovers that may occur between two genes that are far apart on the same chromosome?

Accepted Answer

A single crossover may occur; or two-strand, three-strand, and four-strand double crossovers may occur.

Question 3

Why does the recombination frequency often lead to an underestimation of the true map distance between linked genes?

Accepted Answer

Because map units between linked genes are defined in terms of the crossover frequency, but distances are estimated from the frequency of recombinant phenotypes in genetic crosses. These frequencies are not identical; only odd numbers of double crossover events will show up as recombinant phenotypes.

Question 4

Genes that are linked

Accepted Answer

A)  do not assort independently during meiosis. 
B)  segregate independently during meiosis. 
C)  are always on the X chromosome. 
D)  are on nonhomologous chromosomes. 
E)  segregate to opposite poles during meiosis. 
A)  do not assort independently during meiosis. 
B)  segregate independently during meiosis. 
C)  are always on the X chromosome. 
D)  are on nonhomologous chromosomes. 
E)  segregate to opposite poles during meiosis.

Question 5

A DNA mutation that gives a distinguishable phenotype for a chromosome or gene is a

Accepted Answer

A)  recessive allele. 
B)  genetic marker. 
C)  linkage group. 
D)  lethal mutation. 
E)  parental type. 
A)  recessive allele. 
B)  genetic marker. 
C)  linkage group. 
D)  lethal mutation. 
E)  parental type.

Question 6

Alfred Sturtevant discovered that recombination frequencies could be used as a quantitative measure of the genetic distance between two genes on a genetic map.

Accepted Answer

A) True 
 B)False

Question 7

Is it possible for crossing over to occur between two linked genes and yet all of the resulting offspring have parental genotypes?

Accepted Answer

Yes, if a double cro

Question 8

Interference is a phenomenon in which

Accepted Answer

A)  no double crossovers occur among nearby genes. 
B)  the number of observed double crossovers is greater than the number of expected double crossovers. 
C)  the number of observed double crossovers is less than the number of expected double crossovers. 
D)  the occurrence of one crossover interferes with the formation of another crossover nearby. 
E)  Both C and D 
A)  no double crossovers occur among nearby genes. 
B)  the number of observed double crossovers is greater than the number of expected double crossovers. 
C)  the number of observed double crossovers is less than the number of expected double crossovers. 
D)  the occurrence of one crossover interferes with the formation of another crossover nearby. 
E)  Both C and D

Question 9

A two-point testcross is a cross between

Accepted Answer

A)  a heterozygote for one of two linked genes and a double recessive genotype. 
B)  a heterozygote for one gene and a homozygote for another. 
C)  a double heterozygote for two linked genes and a double recessive genotype. 
D)  individuals with two different genetic markers. 
E)  a double heterozygote for two linked genes and a homozygous dominant genotype. 
A)  a heterozygote for one of two linked genes and a double recessive genotype. 
B)  a heterozygote for one gene and a homozygote for another. 
C)  a double heterozygote for two linked genes and a double recessive genotype. 
D)  individuals with two different genetic markers. 
E)  a double heterozygote for two linked genes and a homozygous dominant genotype.

Question 10

Explain how Creighton and McClintock showed, using evidence from corn, that genetic recombination is associated with the physical exchange of parts between homologous chromosomes.

Accepted Answer

In genetic crosses, they observed two vi

Question 11

One would correct for the effects of multiple crossovers in calculating map distances by applying a linear mapping function.

Accepted Answer

A) True 
 B)False

Question 12

How many phenotypic classes may be generated from a three-point testcross?

Accepted Answer

A)  (3)2 = 9 
B)  (3)3 = 27 
C)  (2)2 = 4 
D)  (2)3 = 8 
E)  It cannot be predicted. 
A)  (3)2 = 9 
B)  (3)3 = 27 
C)  (2)2 = 4 
D)  (2)3 = 8 
E)  It cannot be predicted.

Question 13

The closer two genes are together on a chromosome,

Accepted Answer

A)  the less likely there will be a recombination event between them. 
B)  the less likely they are to be good genetic markers. 
C)  the more likely they are to be epistatic. 
D)  the greater the chance that a double crossover will occur between them. 
E)  the more likely there will be a recombination event between them. 
A)  the less likely there will be a recombination event between them. 
B)  the less likely they are to be good genetic markers. 
C)  the more likely they are to be epistatic. 
D)  the greater the chance that a double crossover will occur between them. 
E)  the more likely there will be a recombination event between them.

Question 14

What does the chi-square test tell us about the linkage of two genes?

Accepted Answer

We can use the chi-square test to test t

Question 15

Why is the probability of a double crossover in two different regions of a chromosome NOT equal to the product of the probabilities of the two events occurring separately?

Accepted Answer

The probability of crossing ov

Question 16

If alleles of different genes always maintain their parental association rather than assorting independently into offspring, this is because

Accepted Answer

A)  they are really alleles of a single gene. 
B)  there was a meiotic error. 
C)  they are on the same chromosome but far apart. 
D)  they are very close together on the same chromosome. 
E)  Mendel's experiments were flawed. 
A)  they are really alleles of a single gene. 
B)  there was a meiotic error. 
C)  they are on the same chromosome but far apart. 
D)  they are very close together on the same chromosome. 
E)  Mendel's experiments were flawed.

Question 17

Describe experimental evidence that proves that crossing over occurs at the 4-chromatid stage of meiosis rather than prior to meiosis.

Accepted Answer

In a haploid organism where all the prod

Question 18

Constructing a linkage map illustrates the exact physical locations of genes on a chromosome.

Accepted Answer

A) True 
 B)False

Question 19

In F2s resulting from a testcross, what percent of recombinant phenotypes is expected if the genes under study are independently assorting?

Accepted Answer

A)  2 
B)  35 
C)  90 
D)  50 
E)  There is no predictable percentage. 
A)  2 
B)  35 
C)  90 
D)  50 
E)  There is no predictable percentage.

Question 20

During a dihybrid cross involving two linked genes, 18 percent of the resulting gametes showed a recombinant genotype. These two linked genes are ________ map units apart.

Accepted Answer

A)  0.18 
B)  180 
C)  32 
D)  18 
E)  1.8 
A)  0.18 
B)  180 
C)  32 
D)  18 
E)  1.8

Exam 6: Extensions of Mendelian Genetic Principles

Testcrosses may be used by geneticists to determine if two genes are linked.

What are the forms of crossovers that may occur between two genes that are far apart on the same chromosome?

Why does the recombination frequency often lead to an underestimation of the true map distance between linked genes?

Genes that are linked

A DNA mutation that gives a distinguishable phenotype for a chromosome or gene is a

Alfred Sturtevant discovered that recombination frequencies could be used as a quantitative measure of the genetic distance between two genes on a genetic map.

Is it possible for crossing over to occur between two linked genes and yet all of the resulting offspring have parental genotypes?

Interference is a phenomenon in which

A two-point testcross is a cross between

Explain how Creighton and McClintock showed, using evidence from corn, that genetic recombination is associated with the physical exchange of parts between homologous chromosomes.

One would correct for the effects of multiple crossovers in calculating map distances by applying a linear mapping function.

How many phenotypic classes may be generated from a three-point testcross?

The closer two genes are together on a chromosome,

What does the chi-square test tell us about the linkage of two genes?

Why is the probability of a double crossover in two different regions of a chromosome NOT equal to the product of the probabilities of the two events occurring separately?

If alleles of different genes always maintain their parental association rather than assorting independently into offspring, this is because

Describe experimental evidence that proves that crossing over occurs at the 4-chromatid stage of meiosis rather than prior to meiosis.

Constructing a linkage map illustrates the exact physical locations of genes on a chromosome.

In F2s resulting from a testcross, what percent of recombinant phenotypes is expected if the genes under study are independently assorting?

During a dihybrid cross involving two linked genes, 18 percent of the resulting gametes showed a recombinant genotype. These two linked genes are ________ map units apart.

Genetics of Bacteria and Bacteriophages

Variations in Chromosome Structure and Number

Advanced Gene Mapping in Eukaryotes

Gene Mapping in Eukaryotes

Quantitative Genetics

Chromosomal Basis of Inheritance

Molecular Evolution

Population Genetics

Non-Mendelian Inheritance

Genetics of Cancer

Genetic Analysis of Development

Regulation of Gene Expression in Eukaryotes

Mendelian Genetics

Regulation of Gene Expression in Bacteria and Bacteriophages

Genomics

Applications of Recombinant DNA Technology

Recombinant DNA Technology

DNA Mutation, DNA Repair, and Transposable Elements

Gene Expression: Translation

Gene Expression: Transcription

Gene Control of Proteins

DNA Replication

DNA: The Genetic Material

Genetics: an Introduction

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