Ch 18 - The Human Genome

Name:

Multiple Choice
Identify the choice that best completes the statement or answers the question.

Which of the following are shown in a karyotype?

a.	homologous chromosomes	c.	autosomes
b.	sex chromosomes	d.	all of the above

Which of the following can be observed in a karyotype?

a.	a change in a DNA base	c.	genes
b.	an extra chromosome	d.	alleles

Human females produce egg cells that have

a.	one X chromosome.	c.	one X or one Y chromosome.
b.	two X chromosomes.	d.	one X and one Y chromosome.

What is the approximate probability that a human offspring will be female?

a.	10%	c.	50%
b.	25%	d.	75%

A human female inherits

a.	two copies of every gene located on the X chromosome.
b.	twice as many sex chromosomes as a human male inherits.
c.	one copy of every gene located on the Y chromosome.
d.	all of the same genes that a human male inherits.

In a pedigree, a circle represents a(an)

a.	male.	c.	child.
b.	female.	d.	adult.

A pedigree can be used to

a.	determine whether a trait is inherited.
b.	show how a trait is passed from one generation to the next.
c.	determine whether an allele is dominant or recessive.
d.	all of the above

Which of the following would you be least likely to see in a pedigree?

a.	All of the symbols are unshaded.	c.	All of the symbols are squares.
b.	All of the symbols are shaded.	d.	About half of the symbols are circles.

Which of the following is caused by a dominant allele?

a.	Huntington disease	c.	Tay-Sachs disease
b.	PKU	d.	none of the above

10.

Which of the following is caused by a dominant allele that expresses itself late in a person’s life?

a.	cystic fibrosis	c.	PKU
b.	sickle cell disease	d.	Huntington disease

11.

A person who has PKU

a.	inherited the recessive allele for the trait from one parent.
b.	inherited the recessive allele for the trait from both parents.
c.	is heterozygous for the trait.
d.	will not pass the allele for the trait to his or her offspring.

12.

Which of the following genotypes result in the same phenotype?

a.	I^AI^A and I^AI^B	c.	I^BI^B and I^AI^B
b.	I^BI^B and I^Bi	d.	I^Bi and ii

13.

If a man with blood type A and a woman with blood type B produce an offspring, what might be the offspring’s blood type?

a.	AB or O	c.	A, B, AB, or O
b.	A, B, or O	d.	AB only

14.

Sickle cell disease is caused by a

a.	change in one DNA base.
b.	change in the size of a chromosome.
c.	change in two genes.
d.	change in the number of chromosomes in a cell.

15.

Which of the following does NOT lead to cystic fibrosis?

a.	missing codon in mRNA	c.	malformed red blood cells
b.	shorter CFTR polypeptide chain	d.	absence of CFTR in cell membrane

16.

People who are heterozygous for sickle cell disease are generally healthy because

a.	they are very likely to get malaria.
b.	they usually have some normal hemoglobin in their red blood cells.
c.	their abnormal hemoglobin usually doesn’t cause their red blood cells to become sickle shaped.
d.	they do not produce abnormal hemoglobin.

17.

Alleles found on the same chromosomes

a.	are dominant.	c.	are linked.
b.	are never separated by recombination.	d.	contain repetitive DNA.

18.

The long stretches of repetitive DNA in chromosomes 21 and 22 are unstable sites

a.	that contain genes.
b.	that do not code for proteins.
c.	that cause genetic disorders.
d.	that do not allow crossing-over to occur.

19.

Most sex-linked genes are located on

a.	the autosomes.
b.	the X chromosome only.
c.	the Y chromosome only.
d.	both the X chromosome and the Y chromosome.

20.

Colorblindness is more common in males than in females because

a.	fathers pass the allele for colorblindness to their sons only.
b.	the allele for colorblindness is located on the Y chromosome.
c.	the allele for colorblindness is recessive and located on the X chromosome.
d.	males who are colorblind have two copies of the allele for colorblindness.

21.

Which of the following statements is true?

a.	Females cannot have hemophilia.
b.	A colorblind boy received the allele for colorblindness from his mother.
c.	A sex-linked allele cannot be dominant.
d.	The mother of a colorblind boy must be colorblind.

22.

Which of the following form(s) a Barr body?

a.	the Y chromosome in a male cell
b.	the X chromosome in a male cell
c.	one of the X chromosomes in a female cell
d.	both of the X chromosomes in a female cell

23.

A cat that has spots of more than one color

a.	has no Barr bodies.	c.	is probably male.
b.	is probably female.	d.	has recessive alleles for coat color.

24.

The failure of chromosomes to separate during meiosis is called

a.	nondisjunction.	c.	Turner’s syndrome.
b.	X-chromosome inactivation.	d.	Down syndrome.

25.

Because the X chromosome contains genes that are vital for normal development, no baby has been born

a.	with one X chromosome.	c.	without an X chromosome.
b.	with three X chromosomes.	d.	with four X chromosomes.

26.

Which of the following combinations of sex chromosomes represents a female?

a.	XY	c.	XXXY
b.	XXY	d.	XX

27.

If nondisjunction occurs during meiosis,

a.	only two gametes may form instead of four.
b.	some gametes may have an extra copy of some genes.
c.	the chromatids do not separate.
d.	it occurs during prophase.

28.

Nondisjunction can involve

a.	autosomes.	c.	homologous chromosomes.
b.	sex chromosomes.	d.	all of the above

29.

Scientists test for alleles that cause human genetic disorders by

a.	making karyotypes.
b.	making DNA fingerprints.
c.	detecting the DNA sequences found in those alleles.
d.	making pedigrees.

30.

The process of DNA fingerprinting is based on the fact that

a.	the most important genes are different among most people.
b.	no two people, except identical twins, have exactly the same DNA.
c.	most genes are dominant.
d.	most people have DNA that contains repeats.

31.

What conclusion CANNOT be made from two DNA fingerprints that show identical patterns of bands?

a.	The DNA from the two DNA fingerprints almost certainly came from the same person.
b.	The DNA from the two DNA fingerprints definitely came from two different people.
c.	The DNA from the two DNA fingerprints was separated by size.
d.	The DNA repeats that formed the bands in each DNA fingerprint are the same length.

32.

Which of the following information CANNOT be obtained from the Human Genome Project?

a.	causes of genetic disorders
b.	amino acid sequences of human proteins
c.	locations of genes on chromosomes
d.	whether an allele is dominant or recessive

33.

The purpose of gene therapy is to

a.	cure genetic disorders.
b.	determine the sequences of genes.
c.	remove mutations from genes.
d.	change dominant alleles to recessive alleles.

34.

Which of the following is the first step in gene therapy?

a.	splicing the normal gene to viral DNA
b.	allowing recombinant viruses to infect human cells
c.	using restriction enzymes to cut out the normal gene from DNA
d.	identifying the faulty gene that causes the disease

35.

Gene therapy is successful if the

a.	viruses carrying the replacement gene infect the person’s cells.
b.	replacement gene is replicated in the person’s cells.
c.	replacement gene is transcribed in the person’s cells.
d.	replacement gene is successfully spliced to viral DNA.

Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.

36.

In a human karyotype, 44 of the chromosomes are autosomes. _________________________

37.

In a human karyotype, 23 chromosome pairs are similar in size and shape. _________________________

38.

In humans, the mother determines the sex of the offspring. _________________________

39.

In a pedigree, if a mother is represented by a shaded circle and a father is represented by a shaded square, their children can be represented by either shaded or unshaded circles or squares. _________________________

40.

If a person has blood type A, he or she cannot receive a blood transfusion from a person with blood type O. _________________________

41.

Two parents who have Huntington disease may produce an offspring who does not have Huntington disease. _________________________

42.

If a cat has both orange and black spots, it is homozygous for the alleles on the X chromosome that code for spot color. _________________________

43.

A person who has Down syndrome has two copies of chromosome 21. _________________________

44.

DNA fingerprinting analyzes sections of DNA that have little or no known function but are similar from person to person. _________________________

45.

To locate genes within the human DNA sequence, scientists look for open reading frames within the sequence. _________________________

Completion
Complete each statement.

46.

In humans, sex is determined by the X and ____________________ chromosomes.

47.

If a couple has five boys, the probability that the next child will be a boy is ____________________.

48.

A(An) ____________________ is a diagram that follows the inheritance of a single gene through several generations of a family.

49.

A person who has ____________________ is unable to break down the amino acid phenylalanine.

50.

The alleles I^A and ____________________ for the ABO blood group are codominant.

51.

People who have sickle cell disease inherited ____________________ copies of the sickle cell allele.

52.

A boy who has hemophilia inherited the disorder from his ____________________.

53.

A Barr body is a turned-off ____________________ chromosome.

54.

A person can be tested for the allele that causes Huntington disease because the _________________________ of that allele is different from that of the normal allele.

55.

In DNA fingerprinting, the DNA probe that is used is ____________________ to the DNA sequence of the repeats.