Question 1

What is the result of the activation of the XIST gene in mammals?

Accepted Answer

A) the inactivation of one of the X chromosomes,which then becomes a Barr body in females 
B) activation of the SRY gene that results in the development of male sexual characteristics 
C) the activation of genes on both X chromosomes in females 
D) the expression of sex-linked traits in males 
A) the inactivation of one of the X chromosomes,which then becomes a Barr body in females 
B) activation of the SRY gene that results in the development of male sexual characteristics 
C) the activation of genes on both X chromosomes in females 
D) the expression of sex-linked traits in males

Question 2

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) healthy female of slightly above-average height 
D) sterile female 
A) masculine characteristics such as facial hair 
B) enlarged genital structures 
C) healthy female of slightly above-average height 
D) sterile female

Question 3

How does the recombination of linked genes contribute to natural selection?

Accepted Answer

A) It reduces genetic variability in a sexually reproducing species. 
B) It eliminates specific alleles in a population. 
C) It maintains genetic variability in a species. 
D) It increases the number of alleles associated with a specific gene. 
A) It reduces genetic variability in a sexually reproducing species. 
B) It eliminates specific alleles in a population. 
C) It maintains genetic variability in a species. 
D) It increases the number of alleles associated with a specific gene.

Question 4

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.
A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below.  
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 
A) 1.5 map units 
B) 3 map units 
C) 6 map units 
D) 15 map units

Question 5

Which of the following events causes recombination between linked genes to occur?

Accepted Answer

A) Mutation that causes one homolog to be different from the other homolog. 
B) Independent assortment of the genes. 
C) Crossovers between the genes results in chromosomal exchange. 
D) Nonrecombinant chromosomes break and then re-join with one another. 
A) Mutation that causes one homolog to be different from the other homolog. 
B) Independent assortment of the genes. 
C) Crossovers between the genes results in chromosomal exchange. 
D) Nonrecombinant chromosomes break and then re-join with one another.

Question 6

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) Nondisjunction occurred in one member of the couple during somatic cell production. 
D) Nondisjunction occurred in one member of the couple during gamete production. 
A) The woman inherited this tendency from her parents. 
B) One member of the couple carried a translocation. 
C) Nondisjunction occurred in one member of the couple during somatic cell production. 
D) Nondisjunction occurred in one member of the couple during gamete production.

Question 7

Which of the following types of diseases is associated with the Philadelphia chromosome?

Accepted Answer

A) chronic myelogenous leukemia 
B) Down syndrome 
C) Klinefetler syndrome 
D) heart disease 
A) chronic myelogenous leukemia 
B) Down syndrome 
C) Klinefetler syndrome 
D) heart disease

Question 8

Which of the following statements best describes the SRY gene?

Accepted Answer

A) It is a gene present on the X chromosome that triggers female development. 
B) It is an autosomal gene that is required for the expression of genes on the Y chromosome. 
C) It is a gene region present on the Y chromosome that triggers male development. 
D) It is an autosomal gene that is required for the expression of genes on the X chromosome. 
A) It is a gene present on the X chromosome that triggers female development. 
B) It is an autosomal gene that is required for the expression of genes on the Y chromosome. 
C) It is a gene region present on the Y chromosome that triggers male development. 
D) It is an autosomal gene that is required for the expression of genes on the X chromosome.

Question 9

A man who is a dwarf due to achondroplasia and has 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.Achondroplasia 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) 100% 
A) 0% 
B) 25% 
C) 50% 
D) 100%

Question 10

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. 
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.

Question 11

What does a frequency of recombination of 50% between two genes 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) Independent assortment of the two genes will not occur. 
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) Independent assortment of the two genes will not occur.

Question 12

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome.The patients have muscles that weaken over time because they have absent or decreased dystrophin,a muscle protein.They rarely live past their 20s.How likely is it for a woman to have this condition?

Accepted Answer

A) Women can never have this condition. 
B) One-half of the daughters of an affected man would have this condition. 
C) One-fourth of the daughters of an affected father and a carrier mother could have this condition. 
D) Very rarely: it is rare that an affected male would mate with a carrier female. 
A) Women can never have this condition. 
B) One-half of the daughters of an affected man would have this condition. 
C) One-fourth of the daughters of an affected father and a carrier mother could have this condition. 
D) Very rarely: it is rare that an affected male would mate with a carrier female.

Question 13

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 alteration or gene mutation 
D) a characteristic trait usually given the discoverer's name 
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 alteration or gene mutation 
D) a characteristic trait usually given the discoverer's name

Question 14

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. 
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.

Question 15

Two autosomal genes have a recombination frequency of 16%.Which of the following conclusions can be drawn regarding these genes?

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 between these two genes cannot occur in the cell during meiosis. 
D) The genes are located on the X chromosome. 
A) The two genes are closely linked on the same chromosome. 
B) The two genes are linked but on different chromosomes. 
C) Recombination between these two genes cannot occur in the cell during meiosis. 
D) The genes are located on the X chromosome.

Question 16

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies in which the eyes of the individual are lighter in color than the normal wild-type red color.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) 100% 
A) 0% 
B) 25% 
C) 50% 
D) 100%

Question 17

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

Accepted Answer

A) sex-linked traits are located on autosomes that affect males more severely than females. 
B) the presence of a Y chromosome often worsens the effects of X-linked mutations. 
C) X chromosomes in males generally have more mutations than X chromosomes in females. 
D) males are hemizygous for the X chromosome. 
A) sex-linked traits are located on autosomes that affect males more severely than females. 
B) the presence of a Y chromosome often worsens the effects of X-linked mutations. 
C) X chromosomes in males generally have more mutations than X chromosomes in females. 
D) males are hemizygous for the X chromosome.

Question 18

A man who is a dwarf due to achondroplasia and has 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.Achondroplasia is autosomal dominant,and red-green color blindness is X-linked recessive.
What proportion of their sons would be color-blind and of normal height?

Accepted Answer

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

Question 19

In humans,clear sex differentiation occurs not at fertilization but after the second month of gestation.What is the first event of this differentiation?

Accepted Answer

A) formation of testosterone in male embryos 
B) formation of estrogens in female embryos 
C) anatomical differentiation of a penis in male embryos 
D) activation of the SRY gene in male embryos and development of testes 
A) formation of testosterone in male embryos 
B) formation of estrogens in female embryos 
C) anatomical differentiation of a penis in male embryos 
D) activation of the SRY gene in male embryos and development of testes

Question 20

Abnormal chromosomes are frequently found in cancerous malignant tumors.Errors such as translocations may place a gene in close proximity to different control regions of the DNA,which can make cells cancerous.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 
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

Exam 12: The Chromosomal Basis of Inheritance

What is the result of the activation of the XIST gene in mammals?

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

How does the recombination of linked genes contribute to natural selection?

Which of the following events causes recombination between linked genes to occur?

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?

Which of the following types of diseases is associated with the Philadelphia chromosome?

Which of the following statements best describes the SRY gene?

Normally,only female cats have the tortoiseshell phenotype because

What does a frequency of recombination of 50% between two genes indicate?

What is a syndrome?

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

Two autosomal genes have a recombination frequency of 16%.Which of the following conclusions can be drawn regarding these genes?

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

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

In humans,clear sex differentiation occurs not at fertilization but after the second month of gestation.What is the first event of this differentiation?

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

Introduction: Evolution and the Foundations of Biology

The Chemical Context of Life

Carbon and the Molecular Diversity of Life

A Tour of the Cell

Membrane Transport and Cell Signaling

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Development,stem Cells,and Cancer

Viruses

Genomes and Their Evolution

Descent With Modification

Phylogeny

The Evolution of Populations

The Origin of Species

Broad Patterns of Evolution

Early Life and the Diversification of Prokaryotes

The Origin and Diversification of Eukaryotes

The Colonization of Land by Plants and Fungi

The Rise of Animal Diversity

Plant Structure and Growth

Resource Acquisition,nutrition,and Transport in Vascular Plants

Reproduction and Domestication of Flowering Plants

Plant Responses to Internal and External Signals

Homeostasis and Endocrine Signaling

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Reproduction and Development

Neurons,synapses,and Signaling

Nervous and Sensory Systems

Motor Mechanisms and Behavior

Population Ecology and the Distribution of Organisms

Ecological Communities

Ecosystems and Energy

Conservation Biology and Global Change

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