Chapter 22

Question 1

If a disorder has a genetic component, a pair of monozygotic twins is ______ dizygotic twins.

Answer 1

more likely to exhibit the disorder than

Question 2

Which statements are true regarding dizygotic twins?

Answer 2

dizygotic twins are formed from separate pairs of sperm and egg cells
dizygotic twins share about 50% of their genetic material

Question 3

Tay-Sachs disease is a genetic disorder caused by a failure in the ______.

Answer 3

breakdown of certain lipids

Question 4

Monozygotic twins ______.

Answer 4

Share 100% of their alleles

Question 5

What is the inheritance pattern when a trait occurs with the same frequency in both sexes and an affected offspring can have two unaffected parents?

Answer 5

autosomal recessie

Question 6

What is the inheritance pattern for a trait that occurs with the same frequency in both sexes and two affected heterozygous individuals have, on average, 25% unaffected offspring?

Answer 6

autosomal dominant

Question 7

What are the three common explanations for autosomal dominant disorders?

Answer 7

Dominant-negative mutations
haploinsufficiency
gain-of-function mutations

Question 8

Which of the following features are characteristic of autosomal recessive inheritance?

Answer 8

Two affected individuals must have affected children
the train occurs in the same frequency in both males and females
An affected offspring can have two unaffected parents

Question 9

Colorblindness is an X-linked recessive trait. A phenotypically normal man and a colorblind woman have two sons. The probability that both of them are colorblind is ______. (Assume no new mutations.)

Answer 9

100%

Question 10

What is the inheritance pattern for a trait that more commonly affects males than females and which will occur in about 50% of the sons born to the unaffected daughter of an affected male?

Answer 10

X-linked recessive

Question 11

Which statement is true of X-linked dominant disorders such as Rett syndrome and Aicardi syndrome?

Answer 11

males die at an early stage of development

Question 12

Hemophilia is an X-linked recessive trait. A heterozygous female is married to a phenotypically normal male. What percentage of their offspring is expected to have hemophilia?

Answer 12

50% of the sons and 0% of the daughters

Question 13

What is the inheritance pattern for a trait that more commonly affects males than females and can often be observed in brothers or fathers of a woman who has affected sons?

Answer 13

X-linked recessive

Question 14

The disease hemophilia is caused by a deficiency in any one of three blood clotting factors. Two of these factors are encoded by genes on the X chromosome and the other clotting factor gene is located on an autosome. Since mutations in more than one gene can cause hemophilia, this represents ______.

Answer 14

locus heterogeneity

Question 15

This figure shows four variable sites along a chromosome that can have any of three different versions, A, B or C, at each site. For this individual, the listing 1C 2C 3C 4A is a ______.

Answer 15

haplotype

Question 16

Hemophilia A is a(n) ______ disorder caused by a defect in the ______.

Answer 16

x-linked recessive
clotting factor VIII

Question 17

A haplotype is a ______.

Answer 17

haploid genotype showing linkage of alleles or molecular markers along a single chromosome

Question 18

What is the inheritance pattern for a trait that is more likely to occur in females when it is lethal to males?

Answer 18

X-linked dominant

Question 19

The first individual to carry a disease-causing allele, from whom the allele spreads throughout portions of the population over time, is known as the ______.

Answer 19

founder

Question 20

Linkage disequilibrium is a(n) ______.

Answer 20

higher level of association between a disease allele and a molecular marker than would be expected by chance

Question 21

A situation where a disease may be caused by mutations in two or more different genes is called ______.

Answer 21

locus heterogeneity

Question 22

Suppose a disease-causing allele shows autosomal recessive inheritance. How could a carrier of this disease-causing allele be identified?

Answer 22

Carriers often show reduced activity for the enzyme encoded by the allele.

Question 23

DNA microarrays can be used to detect ______ that are associated with a disease condition.

Answer 23

single-gene mutations at the DNA level

Question 24

Which methods can be used at the DNA level to test for specific mutations related to a genetic disease?

Answer 24

fluorescence in situ hybridization
DNA sequencing
DNA microarray analysis

Question 25

A signaling molecule that can promote division of cells throughout the body of a multicellular organism is called a(n) ______.

Answer 25

growth factor

Question 26

To stimulate the growth of epidermal cells, such as skin cells, which event would occur first?

Answer 26

An epidermal growth factor, EGF, binds to a receptor on the surface of a skin cell.

Question 27

The proto-oncogene raf codes for an enzyme that participates in a signal transduction pathway promoting cell division. Changing the amino acid valine to glutamic acid at position 599 in the RAF enzyme leads to a type of skin cancer called melanoma. This change from proto-oncogene to oncogene occurred as a result of ______.

Answer 27

missense mutation

Question 28

A growth factor is a ______.

Answer 28

signaling molecule that can stimulate cells throughout the organism's body to divide

Question 29

Chronic myelogenous leukemia is due to production and overexpression of a BCR/ABL fusion protein caused by ______.

Answer 29

translocation of the portion of chromosome 9 carrying the abl gene to the area of chromosome 22 with the bcr gene

Question 30

What is the correct order of events in the normal pathway by which growth factors stimulate cell division? Place the first event at the top.

Answer 30

1. A growth factor binds to a specific receptor on the surface of a cell 2. an intracellular signaling pathway activates cytoplasmic proteins to amplify and carry the signal 3. An activated cytoplasmic protein triggers the activation of transcription factors 4. genes coding for proteins that control cell division are activated

Question 31

How can integration of viral DNA into a host chromosome convert a proto-oncogene into an oncogene?

Answer 31

Viral promoter or enhancer sequences increase transcription of a nearby proto-oncogene.

Question 32

The process of converting a normal cell into a malignant cancer cell is called ______

Answer 32

transformation

Question 33

For chronic myelogenous leukemia, a chromosomal translocation leads to ______.

Answer 33

production of a BCR/ABL fusion protein that promotes division of white blood cells

Question 34

To stimulate the growth of epidermal cells, such as skin cells, which event would occur first?

Answer 34

An epidermal growth factor, EGF, binds to a receptor on the surface of a skin cell.

Question 35

The first example of an oncogene, called Blank______, was discovered as a cause of sarcoma in studies using chicken fibroblast cells.

Answer 35

src

Question 35

The proto-oncogene raf codes for an enzyme that participates in a signal transduction pathway promoting cell division. Changing the amino acid valine to glutamic acid at position 599 in the RAF enzyme leads to a type of skin cancer called melanoma. This change from proto-oncogene to oncogene occurred as a result of ______.

Answer 35

missense mutation

Question 36

Which mechanism accounts for the conversion of c-myc to an oncogene for lymphomas occurring in birds?

Answer 36

DNA from the avian leukosis virus integrates next to the chromosomal c-myc gene and increases its level of transcription.

Question 37

In cancer biology, transformation is the process of ______.

Answer 37

converting a normal cell into a malignant cell

Question 38

Chronic myelogenous leukemia is due to production and overexpression of a BCR/ABL fusion protein caused by ______.

Answer 38

translocation of the portion of chromosome 9 carrying the abl gene to the area of chromosome 22 with the bcr gene

Question 39

During the 1970s, researchers discovered the src gene, an example of an oncogene named for causing the type of cancer called

Answer 39

sarcoma

Question 40

For the non-inherited development of retinoblastoma, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model?

Answer 40

The person is born with two active copies of the rb allele; separate mutation events are required to inactivate each of these alleles.

Question 41

In cells with damaged DNA, DNA repair genes are activated by ______.

Answer 41

p53

Question 42

By the action of tumor suppressor protein p53, which gene shows increased expression to slow progress through the cell cycle and provide time for DNA repair?

Answer 42

p21

Question 43

Apoptosis refers to a controlled series of events called ______.

Answer 43

programmed cell death

Question 44

Caspases are enzymes that ______.

Answer 44

digest cellular proteins during apoptosis

Question 45

Tumor-suppressor genes normally act to ______.

Answer 45

negatively regulate cell division maintain genome integrity

Question 46

In the development of retinoblastoma, a retinal cell is more likely to divide if ______.

Answer 46

both copies of the rb gene are inactivated

Question 47

For the inherited tendency to develop retinoblastoma in the first few years of life, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model?

Answer 47

one allele is inactivated prior to birth, the other becomes inactivated early in life

Question 48

Cellular mechanisms that prevent mutations from occurring and/or prevent mutant cells from dividing or surviving are referred to as genome ______.

Answer 48

maintenance

Question 49

In which two ways have tumor-suppressor genes been shown to act within cells?

Answer 49

regulating the rate of cell division and maintaining genomic integrity

Question 50

Two types of proteins that form activated complexes to promote a cell's progress through the cell cycle are ______.

Answer 50

cyclins and cyclin-dependent protein kinases

Question 51

If the function of Rb protein is lost in a retinal cell, that cell is ______.

Answer 51

more likely to divide

Question 52

The formation of activated cyclin-CDK complexes is regulated by ______.

Answer 52

checkpoint proteins

Question 53

A checkpoint protein ______.

Answer 53

monitors the state of the cell and stops progression through the cell cycle if damage is detected

Question 54

For the non-inherited development of retinoblastoma, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model?

Answer 54

The person is born with two active copies of the rb allele; separate mutation events are required to inactivate each of these alleles.

Question 55

Genome maintenance includes cellular mechanisms that prevent which two processes?

Answer 55

mutation; division or survival of mutant cells

Question 56

Li-Fraumeni syndrome is an inherited tendency toward cancer development that relates to changes in the tumor-suppressor protein p53. A common change is the substitution of tryptophan for arginine at position 248 in the amino acid sequence. This is an example of inactivating a tumor-suppressor gene through ______.

Answer 56

mutation

Question 57

The binding of a specific cyclin and cyclin-dependent protein kinase forms an activated protein complex that ______.

Answer 57

regulates a cell's progress through the cell cycle

Question 58

A series of genetic changes, involving oncogene activation and tumor-suppressor gene inactivation, leads to ______.

Answer 58

malignancy

Question 59

Cancer cells often show ______.

Answer 59

abnormalities in chromosome number and structure

Question 60

In one study of inherited breast cancer, there was a substitution of glycine for cysteine at position 64 in the tumor-suppressor protein BRCA1. This mutation led to cancer development because ______.

Answer 60

the activity of the tumor-suppressor protein was reduced, so it was no longer able to inhibit cell growth

Question 61

According to the accompanying pedigree, what is the inheritance pattern of the allele for inherited breast cancer, BRCA-1?

Answer 61

dominant inheritance with incomplete penetrance

Question 62

Which of the following are detected when visualizing the chromosomes of cancer cells by microscopy?

Answer 62

changes in the number of chromosomes abnormalities in chromosome structure

Question 63

Most individuals who are born with an inherited form of cancer susceptibility are ______ for a defect in a ______.

Answer 63

heterozygous; tumor-suppressor gene

Question 64

Loss of heterozygosity is ______.

Answer 64

loss of function of a normal allele when the other allele was already inactivated

Question 65

If a comparison of two variables shows that they increase together, a positive ________ is demonstrated and, if the results are statistically significant, a true _______ between the variables is suggested.

Answer 65

correlation association

Question 66

The accompanying pedigree shows that breast cancer is inherited with a dominant allele showing incomplete penetrance. This is because ______.

Answer 66

heterozygous individuals show the tendency to develop breast cancer

Question 67

The loss of function of a normal allele when the other allele for that gene was already inactivated is called ______.

Answer 67

loss of heterozygosity

Question 68

Which types of abnormal epigenetic changes have been observed in cancer cells?

Answer 68

covalent modification of histones chromatin remodeling DNA methylation

Question 69

In one study of inherited breast cancer, there was a substitution of glycine for cysteine at position 64 in the tumor-suppressor protein BRCA1. This mutation led to cancer development because ______.

Answer 69

the activity of the tumor-suppressor protein was reduced, so it was no longer able to inhibit cell growth

Question 70

Which of the following is an epigenetic change that would likely lead to cancer?

Answer 70

Hypermethylation inhibits the expression of a tumor-suppressor gene.

Question 71

What causes chromatin modifications to become abnormal and promote cancer?

Answer 71

environmental agents that alter the functions of chromatin-modifying proteins mutations in genes that encode chromatin-modifying proteins

Question 72

The development of cancer could be promoted if an abnormally _____ level of methylation occurred at CpG islands near the start site of a tumor-suppressor gene.

Answer 72

high

Question 73

Mutations in the gene encoding DNA _______an enzyme catalyzing changes that inactivate genes, have been associated with the development of acute myeloid leukemia.

Answer 73

methyltransferase

Question 74

A change in the DNA sequence of the enzyme histone methyltransferase has been observed in renal and breast cancers. These cells are likely to have ______.

Answer 74

a reduction in methyl groups on histones

Question 75

A mutation in a chromatin-modifying protein that contributes to cancer would likely be associated with ______.

Answer 75

open chromatin around an oncogene

Question 76

Cancer can develop as a result of abnormal chromatin modifications caused by increased ______ in genes that encode chromatin-modifying proteins or through the action of _______ agents that alter the functions of chromatin-modifying proteins.

Answer 76

mutations environmental

Question 77

If a mutation in the gene for DNA methyltransferase inhibits the function of this ______change due to a(n) _______ in the level of DNA methylation that can be passed from one cancer cell to its daughter cells.

Answer 77

epigenetic decrease

Question 78

The process of identifying the genes that play a role in the development of a specific type of cancer is called ______.

Answer 78

molecular profiling

Question 79

Which aspects of drug interaction within the body are affected by genetic variation in humans?

Answer 79

drug transport drug metabolism ability of drug to affect its target protein

Question 80

In determining the proper dose of a drug to give a patient, which factors need to be considered? Whether the patient has a gene that ______.

Answer 80

would cause faster metabolism of the drug than in other patients would slow transport of the drug from the digestive system to the bloodstream encodes a target protein with a different shape that will not effectively bind to the drug

Question 81

Which aspects of drug interaction within the body are affected by genetic variation in humans?

Answer 81

ability of drug to affect its target protein drug metabolism drug transport