Deck 13: Chromosomes and Human Genetics

Question 1

The chromosome theory of inheritance states that

A)chromosomes are made of DNA.
B)genes are located on chromosomes.
C)genes are inherited.
D)patterns of inheritance are based on probability.

Answer 1

B

Question 2

Which of the following processes creates new alleles?

A)crossing-over
B)independent assortment
C)mutation
D)random fertilization

Answer 2

C

Question 3

Inheritance is said to be both stable and variable because

A)chromosome structure ensures that the DNA sequence of a chromosome never changes, but allows offspring to inherit individual chromosomes randomly.
B)the process of gamete formation never changes, but the number of chromosomes in a gamete differs in different offspring.
C)most of the time, genetic material is transferred with complete accuracy to the next generation while still creating unique individuals.
D)each new individual is a mixture of different chromosomes, but the same genes are found on every chromosome in that individual.

Answer 3

C

Question 4

Chromosomes are composed of DNA and

A)RNA.
B)alleles.
C)lipids.
D)proteins.

Question 5

Which of the following statements would be true if the linkage between two traits were complete?

A)Only the parental combinations of phenotypes could appear in the progeny.
B)The rules of independent assortment would hold true.
C)Combinations of phenotypes different from those seen in the parents would be produced.
D)The exchange of genetic material between chromosomes would be frequent.

Question 6

What effect does gene linkage have on the overall variety of individuals produced?

A)It increases the probable variation between individuals.
B)It does not affect the probable variation between individuals.
C)It decreases the probable variation between individuals.
D)It causes excessive crossing-over within the genome.

Question 7

The gender of a human child is determined by the

A)loci.
B)autosome.
C)egg.
D)sperm.

Question 8

The "actual results" in the experiment depicted in the figure below differ significantly from the "expected results" predicted by Mendel's laws because the gene for body color and the gene for wing length

A)are both recessive.
B)are close together on a single chromosome.
C)undergo independent assortment.
D)are located on completely opposite ends of the same chromosome.

Question 9

The figure below contains a pedigree for cystic fibrosis, an autosomal recessive disorder. Which of the following is true?

A)At least two of the members of Generation I are carriers of cystic fibrosis.
B)None of the members of Generation II is a carrier of cystic fibrosis.
C)Individual 2 in Generation II has cystic fibrosis.
D)The cystic fibrosis gene is found on a sex chromosome.

Question 10

Chromosomes that are not involved in determining gender are known as

A)autosomes.
B)sex chromosomes.
C)homologous.
D)linked.

Question 11

Which of the following statements about crossing-over is true?

A)It lowers the likelihood of genetic recombination.
B)It disrupts the linkage between genes.
C)It results in the production of extra chromosomes.
D)It is usually fatal.

Question 12

Which of the following processes is not a method of generating new combinations of alleles in the offspring of two individuals?

A)crossing-over between chromosomes
B)fertilization of an egg by a sperm
C)independent assortment of chromosomes
D)linkage of genes

Question 13

What is the effect of the independent assortment of chromosomes on the overall variety of individuals produced?

A)It increases the probable variation between individuals.
B)It does not affect the probable variation between individuals.
C)It decreases the probable variation between individuals.
D)It causes excessive crossing-over within the genome.

Question 14

Which of the following genotypes represents a human female?

A)XY
B)XX
C)YY
D)Zz

Question 15

In humans, the "master switch" that determines whether an embryo will become a male is

A)the X chromosome.
B)the SRY gene.
C)found on chromosome 6.
D)the AB+ gene.

Question 16

We now know that the gene for flower color and the gene for seed color are both on chromosome 1 of the pea plants once studied by Mendel. According to Mendel's results, flower color and seed color undergo independent assortment. Which of the following explanations is most likely?

A)Nonhomologous chromosomes containing the two genes underwent crossing-over to create a new "hybrid" chromosome containing both genes.
B)During a round of meiosis, the female part of a flower failed to separate a homologous pair, forcing the seed-color gene to pair up with the flower-color gene.
C)Between the time that Mendel studied peas and modern times, one of the genes was translocated onto chromosome 1 so that in modern times two genes that were once on separate chromosomes are now linked.
D)These genes are so far apart on chromosome 1 that they undergo independent assortment.

Question 17

Which of the following genetic changes would not be heritable?

A)a mutation in a skin cell
B)the loss of a chromosome in a sperm cell
C)the addition of a chromosome in an egg cell
D)a mutation in a gene in a gamete

Question 18

Because an individual with an XX genotype is a female, is an individual with an XO (no second sex chromosome)a male?

A)No, because the X always overrides the Y and makes that embryo female.
B)No, because the Y chromosome contains the gene that makes an embryo male.
C)Yes, because if there is only one X, the embryo cannot become female.
D)Yes, because all embryos start off as males.

Question 19

Genes that are located on opposite ends of the same chromosome are

A)not affected by crossing-over.
B)affected by crossing-over at the same frequency as genes that are located next to each other on the same chromosome.
C)only affected by cross-over events that occur between two nonhomologous chromosomes.
D)affected by crossing-over so frequently that they may appear to undergo independent assortment.

Question 20

In humans, which of the following chromosomes would probably carry the fewest genes?

A)the Y chromosome
B)chromosome 4
C)the X chromosome
D)chromosome 14

Question 21

The gene for a certain sex-linked trait is found only on the Y chromosome. If the male parent carries this gene, which of the following statements about the inheritance of that trait is true?

A)The trait will be expressed in 100 percent of the female offspring.
B)The trait will be expressed in 50 percent of the female offspring.
C)The trait will be expressed in 100 percent of the male offspring.
D)The trait will be expressed in 50 percent of the male offspring.

Question 22

Even though it is deadly, the Huntington's disease allele can remain in the population, because

A)the dominant allele sometimes reverts to a recessive form.
B)it is sex-linked to the male gamete, and females do not carry the allele.
C)people with the disorder often live long enough to reproduce.
D)it is autosomal and can be masked by a codominant harmless allele.

Question 23

If a genetic disorder is caused by a dominant allele, individuals with which of the following genotypes would be affected by the disorder?

A)AA and aa
B)aa and Aa
C)AA and Aa
D)AA, Aa, and aa

Question 24

An allele that appears to "skip generations" is most likely

A)dominant.
B)recessive.
C)sex-linked.
D)autosomal.

Question 25

If a recessive allele causes a fatal disease that kills the affected individual before he or she can reproduce, why doesn't that allele quickly become extinct in the population?

A)Alleles are never lost from a population.
B)The homozygous dominant individuals protect the recessive allele in their genomes.
C)The recessive allele is carried in the genome of heterozygotes, who do not suffer from the disease.
D)The homozygous recessive individuals give their alleles to other individuals before they die from the disease.

Question 26

Most inherited human disorders are the result of

A)recessive mutations of genes located on autosomes.
B)recessive mutations of genes located on the X chromosome.
C)recessive mutations of genes located on the Y chromosome.
D)simultaneous mutations of the same gene on homologous chromosomes.

Question 27

Both members of a couple are carriers for a recessive disease allele. If the couple has four children, which of the following statements must be true?

A)One of the children has the disease.
B)Two of the children have the disease.
C)All of the male children have the disease.
D)Fifty percent of the children could be carriers of the disease.

Question 28

This chromosomal disorder known as Cri du chat syndrome is the result of missing a part of chromosome 5, an example of chromosome

A)inversion.
B)deletion.
C)translocation.
D)duplication.

Question 29

During translocation,

A)pieces of DNA are exchanged between the non-sister chromatids of a homologous pair.
B)a segment of DNA is broken off of a chromosome and reattached to the same chromosome, but backward in orientation.
C)segments of DNA involved in crossing-over undergo somatic mutations.
D)a segment of DNA breaks off one chromosome and is attached to a nonhomologous chromosome.

Question 30

Down syndrome results from trisomy of chromosome 21. Which of the following is not an example of how this may have happened?

A)translocation of chromosome 21
B)failure of the homologous pair for chromosome 21 to separate in meiosis I
C)inversion of a portion of chromosome 21 during S phase
D)failure of the sister chromatids in a duplicated chromosome 21 to separate in meiosis II

Question 31

The parents in the figure below are carriers of a genetic disorder. Based on the Punnett square, the allele that causes the disorder must
A)

A)be autosomal.
B)be sex-linked.
C)be incompletely dominant.
D)result from the linkage of A and

Question 32

This pedigree diagrams an X-linked gene. The individual indicated by the question mark is _____ for the gene.

A)heterozygous
B)homozygous
C)autosomal
D)There is not enough information to determine the answer.

Question 33

The genetic disorder followed through this pedigree is

A)recessive and X-linked.
B)recessive and not X-linked.
C)dominant and X-linked.
D)dominant and not X-linked.

Question 34

During cell division a piece of a chromosome breaks away and is added to the end of its homologue. This is an example of

A)duplication.
B)inversion.
C)translocation.
D)deletion.

Question 35

Why are X-linked recessive genetic disorders more commonly seen in males?

A)For an X-linked disorder to occur, an individual must receive one allele only found on the X chromosome and a second allele found only on the Y chromosome, which females do not have.
B)Females must receive two copies of the recessive allele to exhibit the disorder, but males need only one copy.
C)The alleles of sex-linked genes are carried only on the Y chromosome, which females do not have.
D)Females only have X chromosomes and genes on the X chromosome are not expressed.

Question 36

The allele responsible for causing Huntington's disease is

A)dominant.
B)recessive.
C)sex-linked.
D)not heritable.

Question 37

Most inherited human genetic disorders are inherited as _____ alleles.

A)dominant
B)autosomal
C)recessive
D)environmental

Question 38

Among children with parents who are both carriers of Tay-Sachs, an autosomal recessive disorder, chances are that

A)75 percent will be carriers.
B)50 percent will die in a few years.
C)75 percent will not carry the recessive Tay-Sachs's allele.
D)50 percent will be carriers.

Question 39

One chromosomal abnormality that is usually fatal is

A)a mutation in a gene on the chromosome.
B)the exchange of material between homologous chromosomes.
C)a change in the number of sex chromosomes.
D)the addition of an extra autosomal chromosome.

Question 40

Which of the following is true of the cross shown in the figure below?

A)All of their daughters will be carriers.
B)Their sons have a 50 percent chance of being carriers.
C)Their sons have a 50 percent chance of having the disorder.
D)Their daughters have a 50 percent chance of having the disorder.

Question 41

The ____________________ gene is responsible for activating many genes involved in "maleness" during embryonic development.

Question 42

An XX individual develops as a male. Which of the following statements offers the most likely explanation?

A)This is the usual situation for an XX individual.
B)This occurs when the sperm does not contribute any genetic material.
C)A piece of a Y chromosome has become attached to one of the X chromosomes.
D)This occurs when the egg does not contribute any genetic material.

Question 43

Which of the following combinations of sex chromosomes would most probably have the most serious effects?

A)XXXX
B)XXY
C)X
D)XX

Question 44

A parent who is a carrier for the recessive autosomal disorder B has the genotype ____________________.

Question 45

Human males have one chromosome that females do not, known as the ____________________ chromosome.

Question 46

The farther apart on the same chromosome that two genes are located, the more likely they are to undergo ____________________.

Question 47

Scientists are able to determine what alleles are present in your DNA because every gene in a human occupies a specific position or ____________________ in your chromosomes.

Question 48

A female who is a carrier of the sex-linked gene A has the genotype ____________________.

Question 49

The tendency to develop diseases, such as cancer and heart disease, is

A)usually the result of a mutation in one gene.
B)the result of new combinations of alleles formed during meiosis.
C)the result of the interaction of multiple genes and environmental factors.
D)the result of multiple mutations caused by crossing-over.

Question 50

A ____________________ is a chart that shows genetic relationships within a family over several generations.

Question 51

All sex-linked genes are either X-linked or _-linked.

Question 52

Except for the circled pair, all the chromosomes in this figure are called ____________________.

Question 53

Two chromosomes that have the same set of genes, but perhaps different versions of those genes, are called ____________________ chromosomes.

Question 54

The diagrams below show the same cell, but the homologous pairs are arranged differently in each diagram. The different arrangements of the homologous pairs in version A as compared with version B provide an example of the concept of ____________________.

Question 55

Which of the following statements is not true with regard to Huntington's disease?

A)The discovery of the gene has led to a test that can identify people who will have the disease before they show symptoms.
B)The disease can be traced using pedigrees.
C)Now that the gene is known, a cure has been found.
D)The gene for Huntington's disease is located on chromosome 4.

Question 56

"New" chromosomes are generated when homologous chromosomes exchange genetic material during ____________________.

Question 57

Which of the following is true with regard to understanding the results of genetic testing?

A)If the test shows that you have the allele for a genetic disorder, you will, eventually, show symptoms of that disorder.
B)If the test shows that you have the allele for a genetic disorder, you may be able to reduce your risk of developing that disorder with lifestyle changes.
C)If the test shows that you do not carry the allele for a particular disorder, there is no chance that you will get that disorder.
D)Because we know the functions of all the genes in the human genome, genetic tests can give you complete and accurate information regarding your medical health.

Question 58

A ____________________ is an individual with a heterozygous genotype who does not express the recessive trait but can pass it along to offspring.

Question 59

Spontaneous abortions are often due to the addition or deletion of whole ____________________ in the gametes that fused to form the zygote.

Question 60

Lethal ____________________ mutations are not eliminated from a population because they can be "hidden" in symptom-free individuals also carrying dominant alleles.

Question 61

Males with a recessive X-linked allele that causes a disorder do not always show symptoms because they can also carry a dominant allele on their Y chromosome.

Question 62

Recessive genetic disorders are quickly eliminated from human populations because people who have them die before they can reproduce.

Question 63

Sex-linked genes are found on either the X chromosome or the Y chromosome but not both.

Question 64

Genes become linked when crossing-over occurs between nonhomologous chromosomes.

Question 65

All genes on the same chromosome are linked.

Question 66

The known human genetic diseases are due to abnormalities located on just a few chromosomes.

Question 67

All diseases are the result of inherited traits.

Question 68

Some of the F₂ gametes involved in the cross below formed as a result of crossing-over.

Question 69

The diagram below depicts the process of translocation.

Question 70

The chance that any two siblings will be genetically identical is astronomically small.

Question 71

Because chromosomal alterations like duplications often affect several genes, they tend to have serious impacts including slowed growth and mental retardation.

Question 72

If DNA testing reveals that you carry alleles for a particular genetic disorder, you will definitely get that disorder at some point in the future.

Question 73

A specific gene can be found in several possible places on a given chromosome.

Question 74

The diagram below demonstrates what happens during a change in chromosomal structure known as a deletion.

Question 75

Ichthyosis is a recessive sex-linked disorder that causes a person's skin to flake off like fish scales. A normal man and a normal woman produce a child with ichthyosis. This child cannot be female.