Question 1

What is the reason that closely linked genes are typically inherited together?

Accepted Answer

A)   The likelihood of a crossover event between these two genes is low.
B)   The number of genes in a cell is greater than the number of chromosomes.
C)   Chromosomes are unbreakable.
D)   Alleles are paired together during meiosis.
E)   Genes align that way during metaphase I of meiosis.

Question 2

Recombination between linked genes comes about for what reason?

Accepted Answer

A)   Mutation on one homolog is different from that on the other homolog.
B)   Independent assortment sometimes fails because Mendel had not calculated appropriately.
C)   When genes are linked they always "travel" together at anaphase.
D)   Crossovers between these genes result in chromosomal exchange.
E)   Nonrecombinant chromosomes break and then re-join with one another.

Question 3

Figure 12.2
-In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in Figure 12.2. What is the order of these genes on a chromosome map?

Accepted Answer

A)   rb-cn-vg-b
B)   vg-b-rb-cn
C)   cn-rb-b-vg
D)   b-rb-cn-vg
E)   vg-cn-b-rb

Question 4

The greatest distance among the three genes is between a and c. What does this mean?

Accepted Answer

A)   Gene c is between a and b.
B)   Genes are in the order: a-b-c.
C)   Gene a is not recombining with c.
D)   Gene a is between b and c.
E)   Distance a-b is equal to distance a-c.

Question 5

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Accepted Answer

A)   The woman inherited this tendency from her parents.
B)   One member of the couple carried a translocation.
C)   One member of the couple underwent nondisjunction in somatic cell production.
D)   One member of the couple underwent nondisjunction in gamete production.
E)   The mother had a chromosomal duplication.

Question 6

Figure 12.1 shows a map of four genes on a chromosome.
  Figure 12.1
-Between which two genes would you expect the highest frequency of recombination?

Accepted Answer

A)   A and W
B)   W and E
C)   E and G
D)   A and E
E)   A and G

Question 7

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?

Accepted Answer

A)   Turner syndrome, 45, X
B)   translocation of SRY to an autosome of a 46, XX individual
C)   a person with an extra X chromosome
D)   a person with one normal and one shortened (deleted)  X
E)   Down syndrome, 46, XX

Question 8

At what point in cell division is a chromosome lost so that, after fertilization with a normal gamete, the result is an embryo with 45, X? I. an error in anaphase I
II)  an error in anaphase II
III)  an error of the first postfertilization mitosis
IV)  an error in pairing

Accepted Answer

A)   I or II only
B)   II or IV only
C)   III or IV only
D)   I, II, or III only
E)   I, II, III, or IV

Question 9

What does a frequency of recombination of 50% indicate?

Accepted Answer

A)   The two genes are likely to be located on different chromosomes.
B)   All of the offspring have combinations of traits that match one of the two parents.
C)   The genes are located on sex chromosomes.
D)   Abnormal meiosis has occurred.
E)   Independent assortment is hindered.

Question 10

Which of the following statements is true of linkage?

Accepted Answer

A)   The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
B)   The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.
C)   All of the traits that Mendel studied-seed color, pod shape, flower color, and others-are due to genes linked on the same chromosome.
D)   Linked genes are found on different chromosomes.
E)   Crossing over occurs during prophase II of meiosis.

Question 11

A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4 that has been exchanged with a portion of his chromosome 12. Although he is normal because his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?

Accepted Answer

A)   One-fourth will be normal, 1/4 will have the translocation, and 1/2 will have duplications and deletions.
B)   All will carry the same translocation as the father.
C)   None will carry the translocation because abnormal sperm will die.
D)   His sperm will be sterile and the couple might consider adoption.
E)   One-half will be normal and the rest will have the father's translocation.

Question 12

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

Accepted Answer

A)   tortoiseshell females; tortoiseshell males
B)   black females; orange males
C)   orange females; orange males
D)   tortoiseshell females; black males
E)   orange females; black males

Question 13

If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

Accepted Answer

A)   1.5 map units
B)   3 map units
C)   6 map units
D)   15 map units
E)   30 map units

Question 14

Which of the following is true of aneuploidies in general?

Accepted Answer

A)   A monosomy is more frequent than a trisomy.
B)   45, X is the only known human live-born monosomy.
C)   Some human aneuploidies have selective advantage in some environments.
D)   Of all human aneuploidies, only Down syndrome is associated with mental retardation.
E)   An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

Question 15

They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?

Accepted Answer

A)   0%
B)   25%
C)   50%
D)   75%
E)   100%

Question 16

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?

Accepted Answer

A)   The frequency of crossing over varies along the length of the chromosome.
B)   The relationship between recombination frequency and map units is different in every individual.
C)   Physical distances between genes change during the course of the cell cycle.
D)   The gene order on the chromosomes is slightly different in every individual.
E)   Linkage map distances are identical between males and females.

Question 17

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

Accepted Answer

A)   The gene involved is on the Y chromosome.
B)   The gene involved is on the X chromosome.
C)   The gene involved is on an autosome, but only in males.
D)   Other male-specific factors influence eye color in flies.
E)   Other female-specific factors influence eye color in flies.

Question 18

What is the greatest benefit of having used a testcross for this experiment?

Accepted Answer

A)   The homozygous recessive parents are obvious to the naked eye.
B)   The homozygous parents are the only ones whose crossovers make a difference.
C)   Progeny can be scored by their phenotypes alone.
D)   All of the progeny will be heterozygous.
E)   The homozygous recessive parents will be unable to cross over.

Question 19

Normally, only female cats have the tortoiseshell phenotype because

Accepted Answer

A)   the males die during embryonic development.
B)   a male inherits only one allele of the X-linked gene controlling hair color.
C)   the Y chromosome has a gene blocking orange coloration.
D)   only males can have Barr bodies.
E)   multiple crossovers on the Y chromosome prevent orange pigment production.

Question 20

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

Accepted Answer

A)   an increase in nondisjunction
B)   expression of inappropriate gene products
C)   a decrease in mitotic frequency
D)   death of the cancer cells in the tumor
E)   sensitivity of the immune system

Exam 12: The Chromosomal Basis of Inheritance

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

Correct Answer
verified

At what point in cell division is a chromosome lost so that, after fertilization with a normal gamete, the result is an embryo with 45, X? I. an error in anaphase I II) an error in anaphase II III) an error of the first postfertilization mitosis IV) an error in pairing

Correct Answer
verified

Normally, only female cats have the tortoiseshell phenotype because

Correct Answer
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Recombination between linked genes comes about for what reason?

Correct Answer
verified

Figure 12.2 -In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in Figure 12.2. What is the order of these genes on a chromosome map?

Correct Answer
verified

Figure 12.1 shows a map of four genes on a chromosome. Figure 12.1 -Between which two genes would you expect the highest frequency of recombination?

Correct Answer
verified

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?

Correct Answer
verified

What is the greatest benefit of having used a testcross for this experiment?

Correct Answer
verified

Correct Answer
verified

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?

Correct Answer
verified

What is the reason that closely linked genes are typically inherited together?

Correct Answer
verified

The greatest distance among the three genes is between a and c. What does this mean?

Correct Answer
verified

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

Correct Answer
verified

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

Correct Answer
verified

What does a frequency of recombination of 50% indicate?

Correct Answer
verified

They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?

Correct Answer
verified

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Correct Answer
verified

Which of the following statements is true of linkage?

Correct Answer
verified

Which of the following is true of aneuploidies in general?

Correct Answer
verified

If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

Correct Answer
verified

Exam 12: The Chromosomal Basis of Inheritance

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

Correct AnswerverifiedShow Answer

At what point in cell division is a chromosome lost so that, after fertilization with a normal gamete, the result is an embryo with 45, X? I. an error in anaphase I II) an error in anaphase II III) an error of the first postfertilization mitosis IV) an error in pairing

Correct AnswerverifiedShow Answer

Normally, only female cats have the tortoiseshell phenotype because

Correct AnswerverifiedShow Answer

Recombination between linked genes comes about for what reason?

Correct AnswerverifiedShow Answer

Figure 12.2 -In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in Figure 12.2. What is the order of these genes on a chromosome map?

Correct AnswerverifiedShow Answer

Figure 12.1 shows a map of four genes on a chromosome. Figure 12.1 -Between which two genes would you expect the highest frequency of recombination?

Correct AnswerverifiedShow Answer

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?

Correct AnswerverifiedShow Answer

What is the greatest benefit of having used a testcross for this experiment?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?

Correct AnswerverifiedShow Answer

What is the reason that closely linked genes are typically inherited together?

Correct AnswerverifiedShow Answer

The greatest distance among the three genes is between a and c. What does this mean?

Correct AnswerverifiedShow Answer

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

Correct AnswerverifiedShow Answer

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

Correct AnswerverifiedShow Answer

What does a frequency of recombination of 50% indicate?

Correct AnswerverifiedShow Answer

They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?

Correct AnswerverifiedShow Answer

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Correct AnswerverifiedShow Answer

Which of the following statements is true of linkage?

Correct AnswerverifiedShow Answer

Which of the following is true of aneuploidies in general?

Correct AnswerverifiedShow Answer

If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

Correct AnswerverifiedShow Answer

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