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 color. 
C)  the Y chromosome has a gene blocking orange coloration. 
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 color. 
C)  the Y chromosome has a gene blocking orange coloration. 
D)  only females can have Barr bodies. 
E)  multiple crossovers on the Y chromosome prevent orange pigment production.

Question 2

How would one explain a testcross involving F₁ dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

Accepted Answer

A)  The two genes are closely linked on the same chromosome. 
B)  The two genes are linked but on different chromosomes. 
C)  Recombination did not occur in the cell during meiosis. 
D)  The testcross was improperly performed. 
E)  Both of the characters are controlled by more than one gene. 
A)  The two genes are closely linked on the same chromosome. 
B)  The two genes are linked but on different chromosomes. 
C)  Recombination did not occur in the cell during meiosis. 
D)  The testcross was improperly performed. 
E)  Both of the characters are controlled by more than one gene.

Question 3

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F₁ males will have cinnabar eyes?

Accepted Answer

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

Question 4

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 
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 5

Why does recombination between linked genes continue to occur?

Accepted Answer

A)  Recombination is a requirement for independent assortment. 
B)  Recombination must occur or genes will not assort independently. 
C)  New allele combinations are acted upon by natural selection. 
D)  The forces on the cell during meiosis II always result in recombination. 
E)  Without recombination there would be an insufficient number of gametes. 
A)  Recombination is a requirement for independent assortment. 
B)  Recombination must occur or genes will not assort independently. 
C)  New allele combinations are acted upon by natural selection. 
D)  The forces on the cell during meiosis II always result in recombination. 
E)  Without recombination there would be an insufficient number of gametes.

Question 6

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. 
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 7

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 
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

Question 8

Refer to the following information to answer the questions below.
A man who is an achondroplastic dwarf with normal vision marries a color-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 color blindness is X-linked recessive.
-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% 
A)  0% 
B)  25% 
C)  50% 
D)  75% 
E)  100%

Question 9

Refer to the following information to answer the questions below.
A man who is an achondroplastic dwarf with normal vision marries a color-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 color blindness is X-linked recessive.
-How many of their daughters might be expected to be color-blind dwarfs?

Accepted Answer

A)  all 
B)  none 
C)  half 
D)  one out of four 
E)  three out of four 
A)  all 
B)  none 
C)  half 
D)  one out of four 
E)  three out of four

Question 10

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?

Accepted Answer

A)  masculine characteristics such as facial hair 
B)  enlarged genital structures 
C)  excessive emotional instability 
D)  normal female 
E)  sterile female 
A)  masculine characteristics such as facial hair 
B)  enlarged genital structures 
C)  excessive emotional instability 
D)  normal female 
E)  sterile female

Question 11

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 12

Correns described that the inheritance of variegated color on the leaves of certain plants was determined by the maternal parent only. What phenomenon does this describe?

Accepted Answer

A)  mitochondrial inheritance 
B)  chloroplast inheritance 
C)  genomic imprinting 
D)  infectious inheritance 
E)  sex-linkage 
A)  mitochondrial inheritance 
B)  chloroplast inheritance 
C)  genomic imprinting 
D)  infectious inheritance 
E)  sex-linkage

Question 13

Which of the following two genes are closest on a genetic map of Drosophila?

Accepted Answer

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

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. 
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

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. 
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 16

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

Accepted Answer

A)  47, +21 
B)  47, XXY 
C)  47, XXX 
D)  47, XYY 
E)  45, X 
A)  47, +21 
B)  47, XXY 
C)  47, XXX 
D)  47, XYY 
E)  45, X

Question 17

Suppose that a gene on human chromosome 18 can be imprinted in a given pattern in a female parent but not in a male parent. A couple in whom each maternal meiosis is followed by imprinting of this gene have children. What can we expect as a likely outcome?

Accepted Answer

A)  All sons but no daughters will bear their mother's imprinting pattern. 
B)  All daughters but no sons will bear their mother's imprinting pattern. 
C)  All sons and daughters will have a 50% chance of receiving the mother's imprinting pattern. 
D)  All the children will bear their mother's imprinting pattern but only daughters will then pass it down. 
E)  Each of the children will imprint a different chromosome. 
A)  All sons but no daughters will bear their mother's imprinting pattern. 
B)  All daughters but no sons will bear their mother's imprinting pattern. 
C)  All sons and daughters will have a 50% chance of receiving the mother's imprinting pattern. 
D)  All the children will bear their mother's imprinting pattern but only daughters will then pass it down. 
E)  Each of the children will imprint a different chromosome.

Question 18

What is a syndrome?

Accepted Answer

A)  a characteristic facial appearance 
B)  a group of traits, all of which must be present if an aneuploidy is to be diagnosed 
C)  a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation 
D)  a characteristic trait usually given the discoverer's name 
E)  a characteristic that only appears in conjunction with one specific aneuploidy 
A)  a characteristic facial appearance 
B)  a group of traits, all of which must be present if an aneuploidy is to be diagnosed 
C)  a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation 
D)  a characteristic trait usually given the discoverer's name 
E)  a characteristic that only appears in conjunction with one specific aneuploidy

Question 19

Use the following information to answer the questions below.
A plantlike organism on the planet Pandora can have 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 recombine as follows:
A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type):
  
-Which of the following are the phenotypes of the parents in this cross?

Accepted Answer

A)  2 and 5 
B)  1 and 6 
C)  4 and 8 
D)  3 and 7 
E)  1 and 2 
A)  2 and 5 
B)  1 and 6 
C)  4 and 8 
D)  3 and 7 
E)  1 and 2

Question 20

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

Accepted Answer

A)  XcXc and XcY 
B)  XcXc and XCY 
C)  XCXC and XcY 
D)  XCXC and XCY 
E)  XCXc and XCY 
A)  XcXc and XcY 
B)  XcXc and XCY 
C)  XCXC and XcY 
D)  XCXC and XCY 
E)  XCXc and XCY

Exam 15: The Chromosomal Basis of Inheritance

Calico cats are female because

How would one explain a testcross involving F₁ dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F₁ males will have cinnabar eyes?

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?

Why does recombination between linked genes continue to occur?

Recombination between linked genes comes about for what reason?

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?

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?

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

Correns described that the inheritance of variegated color on the leaves of certain plants was determined by the maternal parent only. What phenomenon does this describe?

Which of the following two genes are closest on a genetic map of Drosophila?

Which of the following is true of aneuploidies in general?

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?

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

Suppose that a gene on human chromosome 18 can be imprinted in a given pattern in a female parent but not in a male parent. A couple in whom each maternal meiosis is followed by imprinting of this gene have children. What can we expect as a likely outcome?

What is a syndrome?

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

Introduction: Themes in the Study of Life

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

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 Signaling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behavior

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

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