Question 1

A physical map often measures _____, whereas a genetic map measures _____.

Accepted Answer

A)  distances between chromosomes; distances between genes 
B)  map units between genes; physical distances along the chromosome 
C)  centiMorgans; base pairs 
D)  distances in base pairs along the chromosome; centiMorgans 
E)  map units between genes; centiMorgans 
A)  distances between chromosomes; distances between genes 
B)  map units between genes; physical distances along the chromosome 
C)  centiMorgans; base pairs 
D)  distances in base pairs along the chromosome; centiMorgans 
E)  map units between genes; centiMorgans D

Question 2

A situation in which the coefficient of coincidence is greater than 1.0 would indicate that:

Accepted Answer

A)  the interference is high and one crossover suppresses the occurrence of a second one. 
B)  no double crossovers were found in the progeny of a testcross, even though some were expected based on probability. 
C)  double crossovers were found in the progeny of a testcross, but there were fewer of them than would be expected based on probability. 
D)  there were more double crossovers in the progeny than would be expected based on probability. 
E)  the genes involved were actually assorting independently. 
A)  the interference is high and one crossover suppresses the occurrence of a second one. 
B)  no double crossovers were found in the progeny of a testcross, even though some were expected based on probability. 
C)  double crossovers were found in the progeny of a testcross, but there were fewer of them than would be expected based on probability. 
D)  there were more double crossovers in the progeny than would be expected based on probability. 
E)  the genes involved were actually assorting independently. D

Question 3

Assume that you are able to examine a total of 100 separate meiotic events in an animal species. You note that within 10 of these meiotic events, there was a crossover event occurring between genes A and B. In the remaining 90 events there was no crossover event between these two genes. What would be the expected map distance between genes A and B?

Accepted Answer

A)  10 m.u. 
B)  5 m.u. 
C)  20 m.u. 
D)  45 m.u. 
E)  50 m.u. 
A)  10 m.u. 
B)  5 m.u. 
C)  20 m.u. 
D)  45 m.u. 
E)  50 m.u. B

Question 4

Why are the progeny of a testcross generally used to map loci? Why not the F2 progeny from an F1 × F1 cross?

Accepted Answer

A)  Only recombinant offspring would be found in the progeny of an F1 × F1 cross. 
B)  The progeny of an F1 × F1 cross would be found in a 9:3:3:1 ratio when two genes are involved, whereas the progeny of a testcross would result in a 1:1:1:1 ratio. 
C)  It is easier to classify recombinant and parental offspring of a testcross than with the progeny of an F1 × F1 cross. 
D)  In a testcross more of the progeny would be expected to display the dominant phenotype than in the progeny of an F1 × F1 cross. 
E)  A testcross is more useful for mapping genes that are located near each other but, when genes are quite far apart on the same chromosome, an F1 × F1 cross actually is more useful. 
A)  Only recombinant offspring would be found in the progeny of an F1 × F1 cross. 
B)  The progeny of an F1 × F1 cross would be found in a 9:3:3:1 ratio when two genes are involved, whereas the progeny of a testcross would result in a 1:1:1:1 ratio. 
C)  It is easier to classify recombinant and parental offspring of a testcross than with the progeny of an F1 × F1 cross. 
D)  In a testcross more of the progeny would be expected to display the dominant phenotype than in the progeny of an F1 × F1 cross. 
E)  A testcross is more useful for mapping genes that are located near each other but, when genes are quite far apart on the same chromosome, an F1 × F1 cross actually is more useful.

Question 5

Use the following to answer questions :
You just bought two black guinea pigs, one male and one female, of the same genotype from the pet store that are known to be heterozygous (Bb). You also know that black fur (BB) is dominant over white fur (bb) and that a lethal recessive allele is located only 1 m.u. away from the recessive b allele, and your animals are both heterozygous for this gene also.
-What is the probability of finding a white individual among the progeny if you cross these two animals?

Accepted Answer

A)  0.25 
B)  0.0025 
C)  0.000025 
D)  0.005 
E)  0.495 
A)  0.25 
B)  0.0025 
C)  0.000025 
D)  0.005 
E)  0.495

Question 6

A series of two-point crosses among fruit flies is carried out between genes for brown eyes (bw), arc wings (a), vestigial wings (vg), ebony body color (e), and curved wings (cv). The following number of nonrecombinant and recombinant progeny were obtained from each cross: $$\begin{array} { | l l | l | } 
\hline \text { Genes in cross } & \text { Progeny (NR) } & \text { Progeny (R) } \
\hline a , b w & 2224 & 117 \
\hline a , c v & 2609 & 823 \
\hline a , e & 3200 & 3200 \
\hline a , v g & 5172 & 2379 \
\hline b w , c v & 4614 & 1706 \
\hline b w , e & 4150 & 4150 \
b w , v g & 2796 & 1434 \
c v , e & 3116 & 3116 \
c v , v g & 2102 & 305 \
v g ~ e & 4559 & 4559 \
\hline
\end{array}$$ Using these data from two-point crosses, what it the best genetic map (in m.u.) that can be developed?

Accepted Answer

A)  cv 5 bw 13 a 34 vg with e assorting independently 
B)  bw 5 cv 24 vg 32 a with e assorting independently 
C)  a 5 bw 13 vg 24 e with vg assorting independently 
D)  cv 13 bw 5 a 27 vg with e assorting independently 
E)  bw 5 a 24 cv 13 vg with e assorting independently 
A)  cv 5 bw 13 a 34 vg with e assorting independently 
B)  bw 5 cv 24 vg 32 a with e assorting independently 
C)  a 5 bw 13 vg 24 e with vg assorting independently 
D)  cv 13 bw 5 a 27 vg with e assorting independently 
E)  bw 5 a 24 cv 13 vg with e assorting independently

Question 7

Two linked genes, (A) and (B), are separated by 18 m.u. A man with genotype Aa Bb marries a woman who is aa bb. The man's father was AA BB. What is the probability that their first child will be Aa bb?

Accepted Answer

A)  0.18 
B)  0.41 
C)  0.09 
D)  0.25 
E)  0.50 
A)  0.18 
B)  0.41 
C)  0.09 
D)  0.25 
E)  0.50

Question 8

If a three-strand double crossover occurs between two genes during meiosis, what is the expected outcome with respect to these two genes?

Accepted Answer

A)  Two chromatids are parental and two chromatids are recombinant. 
B)  All four chromatid are parental. 
C)  All four chromatids are recombinant. 
D)  Three chromatids are recombinant and one is parental. 
E)  Three chromatids are parental and one is recombinant. 
A)  Two chromatids are parental and two chromatids are recombinant. 
B)  All four chromatid are parental. 
C)  All four chromatids are recombinant. 
D)  Three chromatids are recombinant and one is parental. 
E)  Three chromatids are parental and one is recombinant.

Question 9

Is it possible for two different genes located on the same chromosome to assort independently?

Accepted Answer

A)  No, if two genes are on the same chromosome, they will be linked and the recombination frequency will be less than 50%. 
B)  Yes, if the two genes are close enough to each other, there will be a limited number of crossover events between them. 
C)  No, there will be very high crossover interference such that the recombination frequency will be reduced significantly. 
D)  Yes, if the genes are far enough apart on the same chromosome, a crossover will occur between them in just about every meiotic event. 
E)  Yes, but only if the two genes are both homozygous. 
A)  No, if two genes are on the same chromosome, they will be linked and the recombination frequency will be less than 50%. 
B)  Yes, if the two genes are close enough to each other, there will be a limited number of crossover events between them. 
C)  No, there will be very high crossover interference such that the recombination frequency will be reduced significantly. 
D)  Yes, if the genes are far enough apart on the same chromosome, a crossover will occur between them in just about every meiotic event. 
E)  Yes, but only if the two genes are both homozygous.

Question 10

Linked genes are:

Accepted Answer

A)  allelic. 
B)  dominant. 
C)  on different chromosomes. 
D)  on the same chromosome. 
E)  recessive lethal. 
A)  allelic. 
B)  dominant. 
C)  on different chromosomes. 
D)  on the same chromosome. 
E)  recessive lethal.

Question 11

In flower beetles, pygmy (py) is recessive to normal size (pyS1U1P1+S1S1P0), and red color (r) is recessive to brown (rS1U1P1+S1S1P0). A beetle heterozygous for these characteristics was test-crossed to a beetle homozygous for pygmy and red. The following are progeny phenotypes from this testcross. $$\begin{array} { l l r } 
p y ^ { + } & r ^ { + } & 180 \
p y ^ { + } & r & 22 \
p y & r ^ { + } & 19 \
p y & r & 191 \
\text { Total } && 412
\end{array}$$ Carry out a series of chi-square tests to determine if there is equal segregation of alleles at the py locus.
- What is the correct chi-square value and how many degree(s) of freedom should be used in its interpretation?

Accepted Answer

A)  0.16 with one degree of freedom 
B)  0.16 with three degrees of freedom 
C)  0.48 with one degree of freedom 
D)  0.48 with two degrees of freedom 
E)  4.56 with one degree of freedom 
A)  0.16 with one degree of freedom 
B)  0.16 with three degrees of freedom 
C)  0.48 with one degree of freedom 
D)  0.48 with two degrees of freedom 
E)  4.56 with one degree of freedom

Question 12

Lod scores measure:

Accepted Answer

A)  the relatedness of two individuals. 
B)  the number of crossover events that occur along an entire chromosome. 
C)  how often double crossovers occur. 
D)  the length of a linkage group. 
E)  the likelihood of linkage between genes. 
A)  the relatedness of two individuals. 
B)  the number of crossover events that occur along an entire chromosome. 
C)  how often double crossovers occur. 
D)  the length of a linkage group. 
E)  the likelihood of linkage between genes.

Question 13

Assume that an individual of AB/ab genotype is involved in a testcross and four classes of testcross progeny are found in equal frequencies. Which of the following statements is TRUE?

Accepted Answer

A)  The genes A and B are on the same chromosome and closely linked. 
B)  The genes A and B are on the same chromosome and very far apart. 
C)  The genes A and B are probably between 10 and 20 map units apart on the same chromosome. 
D)  The genes A and B are likely located on different chromosomes. 
E)  The genes A and B could be located on different chromosomes or on the same chromosome and very far apart. 
A)  The genes A and B are on the same chromosome and closely linked. 
B)  The genes A and B are on the same chromosome and very far apart. 
C)  The genes A and B are probably between 10 and 20 map units apart on the same chromosome. 
D)  The genes A and B are likely located on different chromosomes. 
E)  The genes A and B could be located on different chromosomes or on the same chromosome and very far apart.

Question 14

Use the following to answer questions 
You are doing lab work with a new species of beetle. You have isolated lines that breed true for either blue shells and long antenna or green shells and short antenna. Crossing these lines yields FS1U1B11S1U1B0 progeny with blue shells and long antenna. Crossing FS1U1B11S1U1B0 progeny with beetles that have green shells and short antenna yields the following progeny:
Blue shell, long antenna82
Green shell, short antenna78
Blue shell, short antenna37
Green shell, long antenna43
Total240
-A chi-square test is done to test for independent assortment. What is the resulting chi-square value and how many degree(s) of freedom should be used in its interpretation?

Accepted Answer

A)  27.1 and one degree of freedom 
B)  14.9 and three degrees of freedom 
C)  14.9 and two degrees of freedom 
D)  27.1 and three degrees of freedom 
E)  0.42 and two degrees of freedom 
A)  27.1 and one degree of freedom 
B)  14.9 and three degrees of freedom 
C)  14.9 and two degrees of freedom 
D)  27.1 and three degrees of freedom 
E)  0.42 and two degrees of freedom

Question 15

Use the following to answer questions 
You are doing lab work with a new species of beetle. You have isolated lines that breed true for either blue shells and long antenna or green shells and short antenna. Crossing these lines yields FS1U1B11S1U1B0 progeny with blue shells and long antenna. Crossing FS1U1B11S1U1B0 progeny with beetles that have green shells and short antenna yields the following progeny:
Blue shell, long antenna82
Green shell, short antenna78
Blue shell, short antenna37
Green shell, long antenna43
Total240
-Assuming that the genes are linked, what is the map distance between them in m.u.?

Accepted Answer

A)  33.3 m.u. 
B)  25.0 m.u. 
C)  49.5 m.u. 
D)  8.0 m.u. 
E)  The genes are assorting independently. 
A)  33.3 m.u. 
B)  25.0 m.u. 
C)  49.5 m.u. 
D)  8.0 m.u. 
E)  The genes are assorting independently.

Question 16

In addition to determining genotypes, two- and three-factor testcrosses can be used to:

Accepted Answer

A)  map gene loci. 
B)  screen recessive mutants. 
C)  measure heritability. 
D)  determine parental origin. 
E)  determine the physical location of genes. 
A)  map gene loci. 
B)  screen recessive mutants. 
C)  measure heritability. 
D)  determine parental origin. 
E)  determine the physical location of genes.

Question 17

GGHH and ccdd individuals are crossed to each other and the F1 backcrossed to the gghh parent. The 4000 progeny included 1806 GgHh, 1794 gghh, 196 Gghh, and 204 ggHh individuals. GGhh and ggHH individuals are next crossed to each other and the F1 test-crossed to a gghh individual. A total of 1600 offspring appeared in the progeny. How many do you expect to be of GgHh genotype?

Accepted Answer

A)  40 
B)  160 
C)  320 
D)  80 
E)  1600 
A)  40 
B)  160 
C)  320 
D)  80 
E)  1600

Question 18

Recombination frequencies can be calculated by:

Accepted Answer

A)  counting the number of recombinant and parental offspring when an individual who is heterozygous for two genes is involved in a testcross. 
B)  performing a chi-square test on the F2 progeny when an individual who is homozygous for two genes is initially crossed to an individual who is homozygous recessive for these two genes. 
C)  counting the number of offspring who are expressing the dominant phenotype when a heterozygous individual for two genes is involved in a testcross. 
D)  performing a chi-square test of the progeny of a cross between parents who are both heterozygous for the same two genes. 
E)  counting the number of offspring that are found in the cross of an individual who is heterozygous for two genes with another parent who is homozygous dominant for one of these genes and homozygous recessive for the other gene. 
A)  counting the number of recombinant and parental offspring when an individual who is heterozygous for two genes is involved in a testcross. 
B)  performing a chi-square test on the F2 progeny when an individual who is homozygous for two genes is initially crossed to an individual who is homozygous recessive for these two genes. 
C)  counting the number of offspring who are expressing the dominant phenotype when a heterozygous individual for two genes is involved in a testcross. 
D)  performing a chi-square test of the progeny of a cross between parents who are both heterozygous for the same two genes. 
E)  counting the number of offspring that are found in the cross of an individual who is heterozygous for two genes with another parent who is homozygous dominant for one of these genes and homozygous recessive for the other gene.

Question 19

The map distances for genes that are close to each other are more accurate than map distances for genes that are quite far apart because:

Accepted Answer

A)  with genes that are far apart, double crossovers and other multiple-crossover events often lead to lethal recombinants that reduce the number of recombinant progeny. 
B)  with genes that are far apart, double crossovers and other multiple-crossover events often lead to nonrecombinant or parental offspring and thus reduce the true map distance. 
C)  crossover interference will cause more double crossovers and other multiple-crossover events to occur than would be expected and thus result in a higher number of recombinant progeny than expected to occur with genes that are far apart. 
D)  double crossovers and other multiple-crossover events occur more often when genes are close to each other and can be readily detected, so these map distances are more accurate than those for genes that are far apart. 
E)  when genes are far apart, single-crossover recombinant classes are more difficult to detect than when genes are close together. 
A)  with genes that are far apart, double crossovers and other multiple-crossover events often lead to lethal recombinants that reduce the number of recombinant progeny. 
B)  with genes that are far apart, double crossovers and other multiple-crossover events often lead to nonrecombinant or parental offspring and thus reduce the true map distance. 
C)  crossover interference will cause more double crossovers and other multiple-crossover events to occur than would be expected and thus result in a higher number of recombinant progeny than expected to occur with genes that are far apart. 
D)  double crossovers and other multiple-crossover events occur more often when genes are close to each other and can be readily detected, so these map distances are more accurate than those for genes that are far apart. 
E)  when genes are far apart, single-crossover recombinant classes are more difficult to detect than when genes are close together.

Question 20

A testcross is performed on an individual to examine three linked genes. The most frequent phenotypes of the progeny were Abc and aBC, and the least frequent phenotypes were abc and ABC. What was the genotype of the heterozygous individual that is test-crossed with the correct order of the three genes?

Accepted Answer

A)  Abc aBC 
B)  BAC/bac 
C)  bcA/BCa 
D)  aBc/AbC 
E)  bAc/BaC 
A)  Abc aBC 
B)  BAC/bac 
C)  bcA/BCa 
D)  aBc/AbC 
E)  bAc/BaC

A physical map often measures _, whereas a genetic map measures _.

A situation in which the coefficient of coincidence is greater than 1.0 would indicate that:

Why are the progeny of a testcross generally used to map loci? Why not the F₂ progeny from an F₁ × F₁ cross?

Two linked genes, (A) and (B), are separated by 18 m.u. A man with genotype Aa Bb marries a woman who is aa bb. The man's father was AA BB. What is the probability that their first child will be Aa bb?

If a three-strand double crossover occurs between two genes during meiosis, what is the expected outcome with respect to these two genes?

Is it possible for two different genes located on the same chromosome to assort independently?

Linked genes are:

Lod scores measure:

Assume that an individual of AB/ab genotype is involved in a testcross and four classes of testcross progeny are found in equal frequencies. Which of the following statements is TRUE?

In addition to determining genotypes, two- and three-factor testcrosses can be used to:

Recombination frequencies can be calculated by:

The map distances for genes that are close to each other are more accurate than map distances for genes that are quite far apart because:

Introduction to Genetics

Chromosomes and Cellular Reproduction

Basic Principles of Heredity

Sex Determination and Sex-Linked Characteristics

Extensions and Modifications of Basic Principles

Pedigree Analysis, Applications, and Genetic Testing

Chromosome Variation

Bacterial and Viral Genetic Systems

DNA: the Chemical Nature of the Gene

Chromosome Structure and Organelle Dna

DNA Replication and Recombination

Transcription

Rna Molecules and Rna Processing

The Genetic Code and Translation

Control of Gene Expression in Prokaryotes

Control of Gene Expression in Eukaryotes

Gene Mutations and Dna Repair

Molecular Genetic Analysis and Biotechnology

Genomics and Proteomics

Epigenetics

Developmental Genetics and Immunogenetics

Cancer Genetics

Quantitative Genetics

Population Genetics

Evolutionary Genetics

Filters

Exam 7: Linkage, Recombination, and Eukaryotic Gene Mapping

A physical map often measures _____, whereas a genetic map measures _____.

A situation in which the coefficient of coincidence is greater than 1.0 would indicate that:

Why are the progeny of a testcross generally used to map loci? Why not the F2 progeny from an F1 × F1 cross?

Two linked genes, (A) and (B), are separated by 18 m.u. A man with genotype Aa Bb marries a woman who is aa bb. The man's father was AA BB. What is the probability that their first child will be Aa bb?

If a three-strand double crossover occurs between two genes during meiosis, what is the expected outcome with respect to these two genes?

Is it possible for two different genes located on the same chromosome to assort independently?

Linked genes are:

Lod scores measure:

Assume that an individual of AB/ab genotype is involved in a testcross and four classes of testcross progeny are found in equal frequencies. Which of the following statements is TRUE?

In addition to determining genotypes, two- and three-factor testcrosses can be used to:

Recombination frequencies can be calculated by:

The map distances for genes that are close to each other are more accurate than map distances for genes that are quite far apart because:

Introduction to Genetics

Chromosomes and Cellular Reproduction

Basic Principles of Heredity

Sex Determination and Sex-Linked Characteristics

Extensions and Modifications of Basic Principles

Pedigree Analysis, Applications, and Genetic Testing

Chromosome Variation

Bacterial and Viral Genetic Systems

DNA: the Chemical Nature of the Gene

Chromosome Structure and Organelle Dna

DNA Replication and Recombination

Transcription

Rna Molecules and Rna Processing

The Genetic Code and Translation

Control of Gene Expression in Prokaryotes

Control of Gene Expression in Eukaryotes

Gene Mutations and Dna Repair

Molecular Genetic Analysis and Biotechnology

Genomics and Proteomics

Epigenetics

Developmental Genetics and Immunogenetics

Cancer Genetics

Quantitative Genetics

Population Genetics

Evolutionary Genetics

Filters

A physical map often measures _, whereas a genetic map measures _.

Why are the progeny of a testcross generally used to map loci? Why not the F₂ progeny from an F₁ × F₁ cross?