Chapter 14 Mutation, DNA Repair, and Cancer

The four proteins involved in nucleotide excision repair in E. coli are called _____, _____, _____, and _____

UrA; UvrB; UvrC; UvrD

What is a mutagen?

a physical or chemical agent that causes mutations

The p53 protein can arrest the cell cycle t the G1 stage by:

activating genes that encode proteins that stop the cell cycle

Which of the following organisms possess mechanisms that minimize mutations?

all living things

What is gene amplification?

an increase in the number of copies of a gene

In response to severe DNA damage that is too extensive to be repaired, the p53 protein will activate other genes that promote _____

apoptosis

How many genetic changes in a cell lineage typically occur before cancer develops?

at least 10

A point mutation in which one base pair is replaced by another is known as _____ substitution

base

A _____ tumor is precancerous and has not spread throughout the body

benign

How can a chromosomal translocation cause cancer?

by creating an abnormal fusion protein

Agents that increase the likelihood if developing cancer are known as _____

carcinogens

UV light and certain chemicals in cigarette smoke are examples of mutagens called _____ because they are known to cause cancer

carcinogens

Some tumor-suppressor genes encode proteins that test the integrity of the genome and prevent a cell from progressing past a certain stage in the cell cycle. These proteins are termed _____ proteins

checkpoint

what are the causes of induced mutations

chemical agents: changes DNA structure (cigarette smoke) physical agents: UV rays and X-rays

A silent mutation results in a polypeptide with an unchanged amino acid sequence because the genetic code is:

degenerate

what are the common causes of spontaneous mutations

errors in DNA replication toxic metabolic products (free radicals can alter DNA structure) changes in nucleotide structure (purines and deoxyribose can break-isomerization causes mispairing) transposons (when inserted in genome can inactivate gene)

Mutations that occur in noncoding sequences may affect gene _____

expression

A _____ mutation typically inhibits protein function because it changes the amino acid sequence downstream of the mutation site

frameshift

Mutations are essential for the long-term continuity of life because they supply the _____ variation that is the foundation for evolutionary change

gene

Relatively small changes in DNA structure are known as:

gene mutations

The cells that are precursors to gametes, such as egg and sperm cells, are called:

germ line cells

The activity of an oncogene is:

higher than that of the normal gene

Mutations can be divided into two main types. Spontaneous mutations result from abnormalities in biological processes while _____ mutations are caused by environmental agents that enter the cell and alter the structure of the DNA

induced

Which of the following best describes the retinoblastoma (Rb) gene?

it is a tumor-suppressor gene involved in the negative regulation of cell division

Select all of the following that are tumor-suppressor genes

maintaince of genome integrity: - p53 - BCRA-1 and 2 - XPD negative regulation: - RB - NF1 - p16

The process by which cancerous cells spread through the body via the bloodstream or surrounding body tissues is termed _____

metastasis

A specific type of point mutation called a _____ mutation is a base substitution that changes a single amino acid in a polypeptide sequence

missense

Most carcinogens are also:

mutagens

_____ may be chemical, like nitrous acid, or physical, such as UV light, in nature

mutagens

A heritable change in genetic material is known as _____

mutation

A _____ mutation involves a change from a normal codon to a stop codon

nonsense

A mutant gene that results in uncontrolled cell growth is known as _____

oncogene

When oncogenes are _____ compared to proto-oncogenes, they can promote certain types of cancer

overactive

A _____ mutation affects only a single base pair

point

A missense mutation in a _____-_____ can convert it to a cancer-promoting gene if the mutation alters the function of the encoded protein to allow for increased cell division

proto oncogene

A normal gene that can become an oncogene if it is mutated is called a _____-_____

proto oncogene

On occasion, a retrovirus may insert its DNA into a host chromosome near _____-_____. This may result in the overexpression of this type of gene, thereby promoting cancer

proto oncogene

What type of mutation does not alter the amino acid sequence of a polypeptide?

silent

Place the following types of mutations in order from the least effect on polypeptide sequence at the top to the most dramatic effects on polypeptide sequence at the bottom: nonsense, missense, silent

silent missense nonsense

All cells of the body that are not part of the germ line are called _____ cells

somatic

What type of mutation results from abnormalities that naturally occur during biological processes?

spontaneous

Amplification of a proto-oncogene can lead to cancer if it increases:

the amount of protein produced

Where must a mutation occur if it is to directly affect an amino acid sequence?

the coding region of a structural gene

In nucleotide excision repair, what serves as the template for synthesis of new DNA to replace the damaged strand?

the complementary strand of DNA

Somatic mutations are not transmitted to an individual's offspring because:

they do not occur in the gametes

How do nonsense mutations affect protein function?

translation is terminated where the mutation occurs, producing a truncated polypeptide which is unlikely to function correctly

A genetic alteration called a chromosomal _____ occurs when one segment of a chromosome becomes attached to a different chromosome

translocation

An overgrowth of cells is known as _____, which can be benign or become cancerous

tumor

Genes encoding proteins that help prevent cancer are called _____-_____ genes

tumor suppressor

Genes that normally function to prevent cancerous growth are called:

tumor suppressor genes

What type of radiation in nonionizing and only penetrates the surface of biological materials?

ultraviolet light

Cancer is characterized by:

uncontrolled cell division

Which of the following genetic diseases affect DNA repair systems in humans?

- PIBIDS - Cockayne syndrome - Xeroderma pigmentosum

Select all of the following that are true about nucleotide excision repair (NER)

- a region of several nucleotides in the damaged strand is removed from the sequence - the undamaged strand is used as a template to synthesize a normal strand

Arrange the stages of cancer progression in the correct order

Benign growth Malignant growth Metastasis

Tumor-suppressor genes lead to cancer by mutations that:

eliminate their function

Cancer usually affects older people because they are likely to have more:

mutations

Arrange the steps in a growth factor signaling pathway that promotes cell division in the correct order

- a growth factor binds to a receptor and activates it - an intracellular signal transduction pathway is activated - transcription factors in the nucleus are activated - genes that promote cell division are transcribed

Match the location of a mutation with its potential effect on gene expression promoter splice junctions translational regulatory element intergenic region

- a possible increase or decrease in the rate of transcription - possible change in the ability of pre-mRNA to be properly produced - possible change in the ability of protein to be produced from mRNA - not as likely to have an effect on gene expression

Which of the following are ways that ionizing radiation can alter DNA structure?

- base deletion - breaks in one or both DNA strands

Match each protein involved in nucleotide excision repair in E. coli with its function UvrC UvrD DNA polymerase DNA ligase UrvA/UrvB complex

- cuts DNA on both sides of the damaged site - removed the damaged region - synthesizes new DNA to fill in the gap - seals newly synthesized DNA to the original strand - identifies a damaged site

What are the two types of proteins that are responsible for advancing a cell through the phases of the cell cycle?

- cyclins - cyclin-dependent kinases

Chemical mutagens can alter DNA structure by causing:

- deamination of bases - alkylation of bases

Which of the following are ways that chemical mutagens covalently modify the structure of nucleotides?

- deamination of bases - alkylation of bases

Which of the following are examples of ionizing radiation?

- gamma rays - X-rays

Which of the following exhibit nucleotide excision repair (NER)?

- humans - mice - bacteria - plants

What are the typical functions of proteins encoded by genes that may become oncogenes?

- intracellular signaling protein - transcription factor - growth factor receptor

What two mechanisms enable a retrovirus to promote cancer?

- it may carry an oncogene in its genome - it may insert their DNA near proto-oncogenes

Which of the following genetic changes can convert a proto-oncogene into an oncogene?

- missense mutations - retroviral insertions - gene amplifications - chromosomal translocations

A normal proto-oncogene may become an oncogene if it is:

- mutated - translocated - amplified

What are the three most common ways that the function of a tumor-suppressor gene is lost?

- mutation within the gene - loss of the chromosome that carries the gene - abnormal DNA methylation near the gene's promoter

The two main functions of tumor suppressor genes are:

- negative regulation of cell division - maintenance of genome integrity

Match each type of point mutation to its effect on the polypeptide sequence silent mutation missense mutation nonsense mutation frameshift mutation

- no effect - one amino acid is changed to another - an amino acid codon is changed to a stop codon - the amino acid sequence is changed downstream of the mutation

Which of the following genes are oncogenes?

- ras - src - erbB - raf - src - fos - jun

Which of the following are examples of somatic cells?

- skin cells - muscle cells - liver cells

Point mutations affect DNA sequences by:

- substituting one base for another

Arrange the events that occur in nucleotide excision repair in E. coli in the correct order

- the UvrA-UvrB complex identifies a damaged site - UvrC makes cuts on both sides of the damaged site - UvrD binds and removed the damaged region - DNA polymerase synthesizes new DNA to fill the gap - DNA ligase seals the newly synthesized DNA to the original strand

Which of the following are ways that point mutations may alter a gene?

- the base sequence within the gene is changed - a nucleotide added to a gene - a nucleotide is removed from a gene

When the addition or deletion of nucleotides does not occur in a multiple of _____ nucleotides, the result is a frameshift mutation

3

What test is used to evaluate the ability of a substance to cause mutations?

Ames

The p53 protein is a tumor-suppressor gene whose expression is induced in response to _____ damage

DNA

Arrange the vents that occur in the progression of lung cancer in the correct order

Hyperplasia Loss of ciliated cells Dysplasia Metastasis