Chapter 13 - Pre-Lecture

How do point mutations affect DNA sequences?

By substituting one base for another By adding or subtracting a single base pair

In NER, the function of UvrA, UvrB, UvrC, and UvrD is to:

Detect an irregularity in DNA structure Remove a segment of the DNA strand containing the irregularity

This figure illustrates the effects of two types of mutations. Match the Roman numeral to the appropriate mutation. I. II.

I. Germ line II. Somatic Cell

The technique of replica plating allows for the:

Identification of transformed cells

Mutations in noncoding sequences:

May affect gene expression

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

Mice Bacteria Humans Plants

Which of the following proteins is (are) inactive in the epidermal growth factor pathway shown in Figure 8.10?

RAS with GDP bound Myc in its unphosphorylated state

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

The base sequence within the gene is changed A base pair is removed from a gene A nucleotide is added to a gene

How do somatic mutations affect an individual's offspring?

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

A site where two adjacent thymine bases become covalently cross-linked to one another is called a(n) ______ ______

Thymine Dimer

A site where two adjacent thymine bases become covalently cross-linked to one another is called a(n) _____ _____

Thymine dimer

In this figure of a DNA molecule, the circled part indicates a type of mutation known as a(n) _______ _______

Thymine dimer

All living things possess mechanisms allowing them to minimize mutation.

True

New mutations are much more likely to be harmful than beneficial to the individual.

True

Which of the following are physical mutagens?

X-rays UV light

A mutation is best defined as:

a heritable change in the genetic material

Examples of chemical mutagens include nitrous ______, which deaminates bases, and nitrogen ______, which alkylates bases

acid mustard

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

genetic

A mutation changes an alanine codon into a valine codon. This is an example of a:

missense mutation

A heritable change in genetic material is known as a(n) ______

mutation

Nucleotide excision repair (NER) is found in:

prokaryotes and eukaryotes

In this figure of a DNA molecule, the circled part indicates a type of mutation known as a(n) ______ _______

thymine dimer

A common function of a tumor-supressor gene is:

to maintain the integrity of the genome To act as a negative regulator of cell division

A somatic mutation is not transmitted to the offspring of the individual that carries it

true

Match each chemical mutagen with its effect on DNA structure 1. Nitrous acid 2. 5- Bromouracil 3. Nitrogen mustard 4. Benzo(a)pyrene:

1. Deaminates bases 2. Acts as a base analogue 3. Alkylates bases 4. between bases in the DNA double helix and causes additions or deletions

In the Lederberg experiment, bacterial colonies on replica plates were exposed to T1 bacteriophage. The results of this experiment demonstrated that the mutation conferring resistance to the bacteriophage occurred:

Randomly Prior to phage exposure

Nitrous acid, nitrogen mustard, 5-bromouracil, and benzo(a)pyrene are examples of ____ mutagens

chemical

A mutation may affect the amino acid sequence of a polypeptide only if it occurs within the _____ sequence of a gene that specifies a protein

codon or coding

The results of the replica plating experiment performed by Joshua and Esther Lederberg supported their hypothesis that mutations are random events by demonstrating that the tonr mutation:

developed in the original population before exposure to bacteriophages

Induced mutations are caused by:

environmental agents

Nonsense and frameshift mutations generally result in less dramatic changes to a polypeptide sequence than missense mutations.

false

Match the location of a mutation with its potential effect on gene expression. 1. Promoter 2. Splice junctions 3. Translational regulatory element 4. Intergenic region

1. A possible increase or decrease the rate of transcription 2. Possible change in the ability of pre-mRNA to be properly processed 3. Possible change in the ability of protein to be production from mRNA 4. Not as likely to have an effect on gene expression

The original sequence of a DNA molecule is 5'-AACCGGTT-3'. Match each mutated sequence with the correct description of the change that occurred. 1. 5'-AACCCGTT-3' 2. 5'-AACCCGGTT-3' 5'-AACGGTT-3'

1. Base substitution 2. Single base addition 3. Single base deletion

Match each protein involved in nucleotide excision repair in E. coli with its function. 1. UvrC 2. UvrD 3. DNA polymerase 4. DNA ligase 5. UvrA/UvrB complex

1. Cuts DNA on both sides if the damaged site 2. Removes the damaged region 3. Synthesizes new DNA to fill in the gap 4. Seals newly synthesized DNA to the original strand 5. Identifies a damaged site

Consider the following four types of point mutations. Match each to its effect on the polypeptide sequence. 1. Silent mutation 2. Missense mutation 3. Nonsense mutation 4. Frameshift mutation

1. No effect on the amino acid sequence 2. One amino acid is changed to another 3. an amino acid codon is changed to a stop codon 4. The amino acid sequence is changed downstream of the mutation

Match each type of mutation to the image that shows its effects on polypeptide sequence. The original sequence of the DNA is: 5'-ATGGCCGGCCCGAAAGAGACC-3'. 1. 2. 3. 4. 5.

1. No mutation 2. Silent mutation 3. Missense mutation 4. Nonsense mutation 5. Frameshift

Place the following types of mutations in order from the least effect on polypeptide sequence at the top to the most dramatic effect on polypeptide sequence at the bottom. 1. Silent mutation 2. Misssense mutation 3. Nonsense mutation

1. Silent mutation 2. Misssense mutation 3. Nonsense mutation

Consider a germ-line mutation that occurs in a sperm which fertilizes a normal egg to produce a zygote. In the individual that results from this zygote ______% f the cells will contain the mutation, and ______% of the gametes produced by that individual will carry the mutation

100% 50%

A common way to change a proto-oncogene into an oncogene is by:

A missenese mutation a gene amplification a chromosomal translacation

Which of the following mutations is (are) somatic?

A mutation in a skin cell A mutation in a liver cell A mutation in a lung cell

What is a thymine dimer?

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

In the Ames test, you expose S. typhimurium cells that cannot synthesize histidine to compound X, then plate them on a medium lacking histidine. The next day you observe a higher number of colonies on this plate versus the control plate, which has bacteria with no exposure. What reasonable conclusion can you draw?

Compound X is a mutagen

What is the purpose of the Ames test?

Evaluation of the ability of a substance to cause mutation

Mutations that happen in a noncoding DNA sequence of a gene have no effect on its expression.

False

Only bacterial species can repair DNA via nucleotide excision repair (NER).

False

Which of the following are chemical mutagens?

Nitrogen mustard Nitrous acid Ethyl methanesulfonate Benzo[a]pyrene

_____ mutations can cause more dramatic changes to a polypeptide sequence than _____ mutations

Nonsense and frameshift; missense

A key difference between germ-line and somatic mutations is that:

Only germ-line mutations can be passed to offspring

Exposure to chemical mutagens can lead to mutations because chemical mutagens can cause:

inappropriate base pairing during DNA replication insertions and deletions during DNA replication

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 DNA

induced

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 DNA

induced

X-rays and gamma rays are examples of _____ radiation, while ______ radiation includes UV light

ionizing nonionizing

Radiation that is short-wavelength and high energy, and often leads to base deletions and breaks in one or both DNA strands, is termed ______ radiation. On the other hand, ______ radiation has a longer wavelength and lower energy, which penetrates the skin and often leads to thymine dimers.

ionizing; nonionizing

X-rays and ultraviolet light are examples of ____ mutagens

physical

Arrange the events that occur in nucleotide excision repair in E. coli in the correct order. Start with the earliest step on top 1. The UvrA-UvrB complz identifies a damaged site 2. UvrC makes cuts on both sides of the damaged site 3. UvrD binds and removes the damaged region 4. DNA polymerase synthesizes new DNA to fill the gap 5. DNA ligase seals the newly synthesized DNA to the original strand

1. The UvrA-UvrB complz identifies a damaged site 2. UvrC makes cuts on both sides of the damaged site 3. UvrD binds and removes the damaged region 4. DNA polymerase synthesizes new DNA to fill the gap 5. DNA ligase seals the newly synthesized DNA to the original strand

Consider the following wild-type DNA sequence: 5'-CCAAGGTT-3'. Which of the following mutations is a base substitution?

5'-CCCAGGTT-3'

Which of the following statements regarding nucleotide excision repair (NER) are true?

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

If a mutant human gamete participates in fertilization, _____ of the resulting offspring will contain the mutation

All cells

Which of the following organisms have the ability to repair DNA and thus minimize mutations?

All living things

The test, which was developed in the 1970s, to evaluate the ability of a substance to cause mutations is called the _____ test

Ames

Which of the following are TRUE regarding ionizing and nonionizing radiation?

Ionizing radiation is short wavelength with high energy, and nonionizing radiation has longer wavelengths with lower energ Ionizing radiation can penetrate deeply into biological tissue, whereas nonionizing radiation can only penetrate the surface

Mutations outside a gene's coding sequence can affect gene expression. Which of the following sites, when mutated, would affect transcription?

Promoter Operator site

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

The coding region of a protein-encoding 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

n the Ames test, mutagenicity is normally tested on a strain of bacterium (Salmonella typhimurium) that cannot synthesize the amino acid histidine. Therefore, these bacteria require histidine in the growth plate to survive. A researcher performs the Ames test to evaluate the mutagenicity of a newly synthesized compound and notices that Salmonella typhimurium is living on a histidine-free growth plate. What can be concluded from these results?

The newly synthesized compound induces a mutation in the bacteria and the bacteria produce histidine

This figure depicts a(n) ______-_______ mutation

germ - line

A spontaneous mutation

is causes by an abnormality in biological process

Bacterial colonies can be transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth. This technique is known as _______ _______

replica plating

This figure shows the wild-type DNA sequence of a gene, along with two mutated sequences. Based on their effect on the resulting polypeptide, sequence I indicates a(n) _____ mutation, while sequence II highlights a(n) ______ mutation

silent missense

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

sponataneous

Biologists categorize the causes of mutation as ______, which result from errors in normal processes, or induced, which are caused by external agents

spontaneous

A wild-type DNA sequence is 5'-ACACGTTGAT-3'. It is converted to 5'-ACACGTTAAT-3'. This mutation is an example of a base ______

substitution

A chemical mutagen can cause mutation by

the covalent modification of bases acting as a base analogue distorting the structure of the DNA double helix