Ch #14

How do the effects of germ-line mutations in a parent progress over the lifetime of an offspring receiving the mutation?

All of the cells of the individual's body, but only half the gametes produced by that individual will carry the mutation.

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

Ames Test

What is effect of a nonsense mutation to the polypeptide sequence?

Amino acid codon is changed to a stop codon

What is the purpose of the Ames test?

Evaluation of the ability of a substance to cause mutation.

A cancer derived from epithelial cells is called a :

carcinoma

Induced mutations are caused by:

environmental agents

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

oncogene

What are tumor-supressor genes?

p53 and Rb

Sickle-cell disease is caused by missense mutation that affects:

the structure of the hemoglobin protein & the shape of red blood cells. And the tendency of hemoglobin proteins to aggregate when the oxygen concentration is low.

Ultraviolet light can cause the formation of a ________ in DNA.

thymine dimer

A mutation in a germ-line cell has a ________ percent change of being transmitted from parent to child.

50%

How much percent of human cancers are associated with the mutations of the p53 gene?

50%

How can a chromosomal translocation cause cancer?

By creating an abnormal fusion protein

Which type of DNA repair involves an enzyme that recognizes an incorrect structure in a base and restores the base to its original structure?

Direct Repair

True or false: All mutagens are physical agents, such a radiation.

False. Even though many mutagens, such as UV radiation, are physical in nature, there are many chemical agents that can lead to mutation.

What type of mutation is the result of the insertion or removal of nucleotides that does not occur in multiples of three?

Frame-shift mutation (can be one nucleotide change)

The RAS protein is active when it bound to:

GTP

What types of mutations have the least effect on polypeptide sequences? The most? The middle ground?

Least: Silent. Middle: Missense. Most: Nonsense

Which DNA repair system detects and repairs base pairs that are not bonded correctly?

Methyl-directed mismatch repair

What type of mutation changes a single amino acid in a polypeptide sequence?

Missense Mutation

What is effect of a silent mutation to the polypeptide sequence?

None.

A ____________ mutation involves a change from a normal codon to a stop codon.

Nonsense mutation

Which DNA repair system can correct a variety of types of DNA damage, including thymine dimers, missing bases, and chemically modified bases?

Nucleotide excision repair.

Mutations outside a gene's coding sequence can affect gene expression. Which sites, when mutation, would affect transcription?

Promoter & Operator site

What type of mutation has no effect on the amino acid sequence of a polypeptide?

Silent mutations

What is effect of a frame-shift mutation to the polypeptide sequence?

The amino acid sequence is changed downstream of the mutation

Silent mutations have no effect on the amino acid sequence of a polypeptide because:

The base substitution results in a codon that specifics the same amino acid as the original sequence

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

The coding region of a structural gene

How do somatic mutations affect an inidvidual's offspring?

The mutation does not occur in germ-line cells and therefore does NOT affect offspring.

What does a gene mutation affect?

The sequence of bases in a particular gene.

How do nonsense mutations affect protein function?

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

True or False: The earlier in development a somatic mutation occurs, the larger the patch of tissue that will be affected by that mutation.

True

True or false: The earlier in development a somatic mutation occurs, the larger the patch of tissue that will be affected by that mutation.

True

True or false: All living things possess mechanisms allowing them to minimize mutation.

True.

Which genetic diseases affect DNA repair systems in humans?

Xeroderma pigmentosum, Cockayne syndrome

A point mutation in which one base pair is replaced by another is known as a:

base substitution

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:

checkpoint proteins

The effects of_______ on DNA structure is varied. Some can alkylate bases, others act as base analogues, and a few can insert between bases in the double helix and cause additions or deletions.

chemicsal mutagens

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

degenerate

Germ-line mutations may occur in:

egg or sperm cells, or in precursor cells that produce them.

In the Ames test, rat liver extract is included because liver___________ sometimes convert chemicals into mutagens.

enzymes

Relatively small changes in DNA sequence are known as:

gene mutations

Mutations are essential for the long-term continuity of life because the supply the __________ that is the foundation for evolutionary change.

genetic variation

The Ames Test uses a strain of Salmonella typhimurium that cannot synthesize:

histidine

X-rays and gamma rays are examples of __________, which is a type of electromagnetic radiation that can create free radicals.

ionizing radiation

Mutations in non-coding sequences:

may affect gene expression

When the promotor of a tumor-suppressor gene undergoes abnormal ________________, the transcription of the gene is usually inhibitied.

methylation

An individual with somatic regions that are genetically different from each other is best known as a :

mosaic

Agents that cause mutation are known as:

mutagens

A heritable change in genetic material is known as:

mutation

The two main functions of tumor suppressor genes are:

negative regulation of cell division maintenance of genome integrity

Researchers have identified many types of ________, such as growth factor receptors, transcription factors, and intracellular signaling proteins.

oncogenes

What is effect of a missense mutation to the polypeptide sequence?

one amino acid is changed to another

The protein product of what tumor-suppressor gene acts to sense DNA damage, promote DNA repair, and halt cell division?

p53

X-rays and ultraviolet light are examples of _________ mutagens

physical

A ___________ mutation affects only a single base pair.

point mutation

A _______ is a tumor of connective tissue such as bone or cartilage.

sarcoma

All cells of the body that are not part of the germ line are called____________

somatic cells

Sperm and egg cells are termed germ line cells. In contrast, cells of the skin, muscle, heart, and liver are examples of_______________

somatic cells

Non-ionizing radiation, such as ultraviolet light, can lead to:

the formation of a thymine dimer

A _____________ is a site where two adjacent thymine bases become covalently cross-linked to one another.

thymine dimer.

A nonsense mutation causes the:______________ of the protein to be terminated prematurely. This reduces the length of the polypeptide and alters its function.

translation

An overgrowth of cells is known as a ___________, which can be benign or become cancerous.

tumor

What type of radiation is non-ionizing and only penetrates the surface of biological materials?

ultraviolet light

How does a missense mutation cause red blood cells to sickle?

Glutamic acid is changed to valine, altering the structure of the hemoglobin protein and causing the hemoglobin subunits to stick to one another.

What is one of the ways chemical mutagens may alter DNA structure?

Insertion of molecules between existing bases. (alkylation of bases, deamination of bases)

What is true about ionizing and non-ionzing radiation?

Ionizing radiation is a short wavelength with high energy that penetrates deeply into biological tissue. Nonionizing radiation has longer wavelengths with low energy that can only penetrate the surface.

How does a frameshift mutation affect protein function?

Protein function is most likely inhibited because an entirely new amino acid sequence occurs downstream of the mutation.

What is the process in which bacterial colonies are transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth?

Replica plating

Point mutations affect DNA sequences by:

base substitution (substituting one base for another, or adding/subtract a single base pair)

Agents that increased the likelihood of developing cancer are known as:

carcinogens

____________ enzymes that are activated during programmed cell death (apoptosis) to digest certain cellular proteins such as actin filaments.

caspase

What is the effect on gene expression if there is a mutation at the splice junctions?

change in the ability of PRE-mRNA to be produced

What is the effect on gene expression if there is a mutation at the translation regulatory elements?

change in the ability of a PROTEIN to be produced from mRNA.

Gametes are produced by:

germ-line cells

Geneticists classify cells of animals into two types:

germ-line cells, and somatic cells

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

the complementary strand of DNA

What are causes of spontaneous mutations?

Errors made by DNA polymerase during replication. Free radicals produced during metabolic processes that change nucleotide structure. Insertion of a transposon into a gene.

What two mechanisms enable a retro virus to promote cancer?

Retrovirus DNA is near proto-oncogenes. Or the retrovirus may carry an oncogene in its genome.

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

Spontaneous

What missense mutation is least likely to affect protein function?

Substitution of a positively charged amino acid for another positively charged amino acid

Apoptosis is a term that refers to:

programmed cell death

Considering the following wild-type DNA sequence: 5'-CCAAGGTT-3'. What would be a base substitution?

5'-CCCAGGTT-3'

Why does cancer affect people more as they age?

Cancer involves a series of mutations that take time to accumulate in a cell lineage.

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

Cyclins and Cyclin-dependent kinases

Nucleotide excision repair (NER) is found in:

prokaryotes and eukaryotes

What is a thymine dimer?

A site where two adjacent thymine bases become covalently cross-linked to each other.

What are chemical mutagens?

Benzopyrene, Nitrous acid, Nitrogen mustard, Ethyl methanesulfonate

What are ways that ionizing radiation can alter DNA structure?

Breaks in one or both DNA strands & base deletion.

A mutation is best defined as:

a heritable change in the genetic material