Question 1

Calico cats are female because

Accepted Answer

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

Question 2

Three genes at three loci are being mapped in a particular species.Each has two phenotypes,one of which is markedly different from the wild type.The unusual allele of the first gene is inherited with either of the others about 50% of the time.However,the unusual alleles of the other two genes are inherited together 14.4% of the time.Which of the following describes what is happening?

Accepted Answer

A) The genes are showing independent assortment. 
B) The three genes are linked. 
C) The first gene is linked but the other two are not. 
D) The first gene is assorting independently from the other two that are linked. 
E) The first gene is located 14.4 units apart from the other two. 
A) The genes are showing independent assortment. 
B) The three genes are linked. 
C) The first gene is linked but the other two are not. 
D) The first gene is assorting independently from the other two that are linked. 
E) The first gene is located 14.4 units apart from the other two. D

Question 3

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome.What is this alteration called?

Accepted Answer

A) deletion 
B) transversion 
C) inversion 
D) translocation 
E) duplication 
A) deletion 
B) transversion 
C) inversion 
D) translocation 
E) duplication D

Question 4

A recessive allele on the X chromosome is responsible for red-green color blindness in humans.A woman with normal vision whose father is color blind marries a color-blind male.What is the probability that this couple's first son will be color blind?

Accepted Answer

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

Question 5

Refer to the following information to answer the questions below.
A man who is an achondroplastic dwarf with normal vision marries a colour-blind woman of normal height.The man's father was 6 feet tall,and both the woman's parents were of average height.Achondroplastic dwarfism is autosomal dominant,and red-green colour blindness is X-linked recessive.
-They have a daughter who is a dwarf with normal colour vision.What is the probability that she is heterozygous for both genes?

Accepted Answer

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

Question 6

Women (and all female mammals)have one active X chromosome per cell instead of two.What causes this?

Accepted Answer

A) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive 
B) activation of the Barr gene on one of the two X chromosomes that then inactivates 
C) crossover between the XIST gene on one X chromosome and a related gene on an autosome 
D) inactivation of the XIST gene on the X chromosome derived from the male parent 
E) the removal of methyl (CH₃)groups from the X chromosome that will remain active 
A) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive 
B) activation of the Barr gene on one of the two X chromosomes that then inactivates 
C) crossover between the XIST gene on one X chromosome and a related gene on an autosome 
D) inactivation of the XIST gene on the X chromosome derived from the male parent 
E) the removal of methyl (CH₃)groups from the X chromosome that will remain active

Question 7

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 colour in flies. 
E) Other female-specific factors influence eye colour in flies. 
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 colour in flies. 
E) Other female-specific factors influence eye colour in flies.

Question 8

In humans,male-pattern baldness is controlled by an autosomal gene that occurs in two allelic forms.Allele Hn determines nonbaldness,and allele Hb determines pattern baldness.In males,because of the presence of testosterone,allele Hb is dominant over Hn.If a man and woman both with genotype HnHb have a son,what is the chance that he will eventually be bald?

Accepted Answer

A) 0% 
B) 25% 
C) 33% 
D) 50% 
E) 75% 
A) 0% 
B) 25% 
C) 33% 
D) 50% 
E) 75%

Question 9

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 
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 10

In birds,sex is determined by a ZW chromosome scheme.Males are ZZ and females are ZW.A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons.What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?

Accepted Answer

A) 2:1 male to female 
B) 1:2 male to female 
C) 1:1 male to female 
D) 4:3 male to female 
E) 3:1 male to female 
A) 2:1 male to female 
B) 1:2 male to female 
C) 1:1 male to female 
D) 4:3 male to female 
E) 3:1 male to female

Question 11

A man who carries an allele of an X-linked gene will pass it on to whom?

Accepted Answer

A) all of his daughters 
B) half of his daughters 
C) half of his sons 
D) all of his sons 
E) all of his children 
A) all of his daughters 
B) half of his daughters 
C) half of his sons 
D) all of his sons 
E) all of his children

Question 12

What is the source of the extra chromosome 21 in an individual with Down syndrome?

Accepted Answer

A) nondisjunction in the mother only 
B) nondisjunction in the father only 
C) duplication of the chromosome 
D) nondisjunction in either parent 
E) It is impossible to detect with current technology. 
A) nondisjunction in the mother only 
B) nondisjunction in the father only 
C) duplication of the chromosome 
D) nondisjunction in either parent 
E) It is impossible to detect with current technology.

Question 13

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. 
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 14

Males are more often affected by sex-linked traits than females because

Accepted Answer

A) male hormones such as testosterone often alter the effects of mutations on the X chromosome. 
B) female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. 
C) X chromosomes in males generally have more mutations than X chromosomes in females. 
D) males are hemizygous for the X chromosome. 
E) mutations on the Y chromosome often worsen the effects of X-linked mutations. 
A) male hormones such as testosterone often alter the effects of mutations on the X chromosome. 
B) female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. 
C) X chromosomes in males generally have more mutations than X chromosomes in females. 
D) males are hemizygous for the X chromosome. 
E) mutations on the Y chromosome often worsen the effects of X-linked mutations.

Question 15

If nondisjunction occurs in meiosis II during gametogenesis,what will be the result at the completion of meiosis?

Accepted Answer

A) All the gametes will be diploid. 
B) Half of the gametes will be n + 1, and half will be n - 1. 
C) 1/4 of the gametes will be n + 1, 1/4 will be n - 1, and 1/2 will be n. 
D) There will be three extra gametes. 
E) Two of the four gametes will be haploid, and two will be diploid. 
A) All the gametes will be diploid. 
B) Half of the gametes will be n + 1, and half will be n - 1. 
C) 1/4 of the gametes will be n + 1, 1/4 will be n - 1, and 1/2 will be n. 
D) There will be three extra gametes. 
E) Two of the four gametes will be haploid, and two will be diploid.

Question 16

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways?

Accepted Answer

A) There are four major functional classes of genes in Drosophila. 
B) Drosophila genes cluster into four distinct groups of linked genes. 
C) The overall number of genes in Drosophila is a multiple of four. 
D) The entire Drosophila genome has approximately 400 map units. 
E) Drosophila genes have, on average, four different alleles. 
A) There are four major functional classes of genes in Drosophila. 
B) Drosophila genes cluster into four distinct groups of linked genes. 
C) The overall number of genes in Drosophila is a multiple of four. 
D) The entire Drosophila genome has approximately 400 map units. 
E) Drosophila genes have, on average, four different alleles.

Question 17

Chimpanzees,gorillas,and orangutans have DNA sequences that are almost identical to those of humans; however,these genes are found on 24 pairs of chromosomes in apes,while humans have 23 pairs.The C2 chromosome in humans is a large chromosome with similar banding pattern and DNA sequences to two smaller chromosomes in apes (C2 and C4).In addition it appears to have both a vestigial second centromere and telomere sequences in the middle of the strand.
-It is believed that early hominins interbred with each other.Ancient humans may have successfully mated with both Neanderthal and Denisovans.What must be true of these species for this to occur?
They must have

Accepted Answer

A) been triploid. 
B) had 23 pairs of chromosomes. 
C) actually been human. 
D) had 24 chromosomes, so nondisjunction could occur. 
E) had wild type phenotypic traits identical to humans. 
A) been triploid. 
B) had 23 pairs of chromosomes. 
C) actually been human. 
D) had 24 chromosomes, so nondisjunction could occur. 
E) had wild type phenotypic traits identical to humans.

Question 18

Thomas Hunt Morgan's choice of Drosophila melanogaster has been proven to be useful even today.Which of the following has/have continued to make it a most useful species?
I.its four pairs of chromosomes
II.a very large number of visible as well as biochemically mutant phenotypes
III.easy and inexpensive maintenance
IV.short generation time and large number of offspring

Accepted Answer

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

Question 19

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 colour, pod shape, flower colour, 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. 
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 colour, pod shape, flower colour, 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 20

Use the following information to answer the questions below.
A plant-like organism on the planet Pandora has three recessive genetic traits: bluish leaves,due to an allele (a)of gene A; a feathered stem,due to an allele (b)of gene B; and hollow roots due to an allele (c)of gene C.The three genes are linked and,when a geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits,she was able to identify progeny with the following phenotypic distribution (+ = wild type):
  
-In which progeny phenotypes has there been recombination between genes A and B?

Accepted Answer

A) 1, 2, 5, and 6 
B) 1, 3, 6, and 7 
C) 2, 4, 5, and 8 
D) 2, 3, 5, and 7 
E) in all 8 of them 
A) 1, 2, 5, and 6 
B) 1, 3, 6, and 7 
C) 2, 4, 5, and 8 
D) 2, 3, 5, and 7 
E) in all 8 of them

Exam 15: The Chromosomal Basis of Inheritance

Calico cats are female because

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome.What is this alteration called?

A recessive allele on the X chromosome is responsible for red-green color blindness in humans.A woman with normal vision whose father is color blind marries a color-blind male.What is the probability that this couple's first son will be color blind?

Women (and all female mammals)have one active X chromosome per cell instead of two.What causes this?

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?

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

A man who carries an allele of an X-linked gene will pass it on to whom?

What is the source of the extra chromosome 21 in an individual with Down syndrome?

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

Males are more often affected by sex-linked traits than females because

If nondisjunction occurs in meiosis II during gametogenesis,what will be the result at the completion of meiosis?

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways?

Which of the following statements is true of linkage?

Introduction: Evolution and Themes of Biology

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

Membrane Structure and Function

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Molecular Basis of Inheritance

From Gene to Protein

Regulation of Gene Expression

Viruses

DNA Tools and Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonized Land

Plant Diversity II: The Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Plant Structure,Growth,and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons,Synapses,and Signalling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behaviour

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

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