Deck 11: Chromosomes and Human Genetics

Question 1

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 may genes and environmental factors.
D) the result of multiple mutations caused by crossing over.

Answer 1

A

Question 2

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.

Answer 2

B

Question 3

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.

Answer 3

B

Question 4

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 5

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

A) At least one of the members of Generation 1 is a carrier of cystic fibrosis.
B) None of the members of Generation 2 is a carrier of cystic fibrosis.
C) Individual 2 in Generation 2 has cystic fibrosis.
D) The cystic fibrosis gene is found on a sex chromosome.

Question 6

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.

Question 7

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 8

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 9

Which of the following genotypes represents a human female?

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

Question 10

Chromosomes that are not involved in determining gender are known as

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

Question 11

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 12

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 13

The "actual results" in the experiment depicted in the figure below differ significantly from the "expected results" predicted by Mendel's laws.
This variation from the expected results probably occurs 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 14

Most inherited human genetic disorders are caused by

A) crossing-over.
B) autosomal sex chromosomes.
C) mutations of single genes.
D) environmental effects.

Question 15

The gender of a human child is determined by the

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

Question 16

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 17

Chromosomes are composed of DNA and

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

Question 18

Which of the following processes creates new alleles?

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

Question 19

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 20

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.

Question 21

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 22

If a female carrier of a recessive X-linked gene (genotype XᴬXᵃ) that causes a disorder mates with a normal male (genotype XᴬY),

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 23

During cell division a piece of a chromosome breaks away and becomes part of its homologue. This is an example of

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

Question 24

Examine the figure below of a pedigree that diagrams an X-linked gene.
The genotype of the individual next to the question mark is

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

Question 25

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 26

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

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

Question 27

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 28

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 don't 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 29

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 30

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 31

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 32

Among children with parents who are both carriers of a 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-Sach's allele.
D) 50 percent will be carriers.

Question 33

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 34

Both members of a couple are carriers for a recessive disease allele. If the couple has four children, which of the following 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 35

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 36

Since 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 37

The allele responsible for causing Huntington's disease is

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

Question 38

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

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

Question 39

Examine the figure below, which shows a pedigree.
The gene diagrammed here is

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

Question 40

This figure shows a pattern of inheritance.
The disorder shown in the figure

A) is autosomal.
B) is sex-linked.
C) displays incomplete dominance.
D) results from the linkage of A and

Question 41

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

Question 42

Each chromosome is made up of several molecules of DNA.

Question 43

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

Question 44

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 45

Mutations that cause genetic disorders have been found on all human chromosomes except the _ chromosome.

Question 46

All organisms determine sex with X and Y chromosomes.

Question 47

Mary's mother is diagnosed with Huntington's disease while Mary is in the first trimester of her first pregnancy. Mary is tested and finds that she carries the Huntington's allele. Mary decides to have amniocentesis because amniocentesis

A) will cure Huntington's disease if it is done early enough in pregnancy.
B) will allow Mary to determine if her child also carries the Huntington's allele.
C) will let Mary know which of her eggs carry the Huntington's allele.
D) is the only way to determine if Mary's husband also has the Huntington's allele.

Question 48

A parent that is a carrier for the recessive autosomal disorder B has the genotype __________.

Question 49

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

Question 50

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

Question 51

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

Question 52

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

Question 53

The physical location of a gene on a chromosome is its _______.

Question 54

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

Question 55

The two classes of chromosomes are sex chromosomes and ____________.

Question 56

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 57

Newborns are required by all 50 states to get 29 different genetic tests. What is the benefit of these tests?

A) The test results help insurance companies to determine whether a child is eligible for coverage.
B) Knowing about a condition before its symptoms arise allows doctors to take preventative measures.
C) Genetic tests can clearly demonstrate whether or not a mother used drugs during pregnancy.
D) These genetic tests determine the true paternity (father) of every child born.

Question 58

During ______ _______ diagnosis, cells are removed from the early embryo and tested for genetic disorders before being implanted in the uterus.

Question 59

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

Question 60

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

Question 61

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

Question 62

All genes on the same chromosome are linked.

Question 63

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

Question 64

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

Question 65

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

Question 66

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

Question 67

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

Question 68

All diseases are the result of inherited traits.

Question 69

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

Question 70

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. What is the sex of the child? Explain your answer.