Chapter 8

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Questions and Answers

Which scientist observed that kernel colors in corn were not inherited in a predictable manner?

Sarah Salm

Barbara McClintock (correct)

Mira Beins

Denise Anderson

What term did Barbara McClintock use to describe the segments of DNA that moved in and out of genes involved in color?

Jumping genes

Transposons (correct)

Mutation

Vertical gene transfer

Which organism is often used as a model system of genetic change?

Bacteria

Corn

E. coli (correct)

Humans

What are the two mechanisms of genetic change in bacteria?

Mutation and horizontal gene transfer Signup and view all the answers

When were the results of Barbara McClintock's research on kernel colors in corn published?

1950 Signup and view all the answers

Which type of molecule intercalates between adjacent bases in a DNA strand?

Flat molecules Signup and view all the answers

What is the result of intercalating agents increasing frameshift mutations?

Increased chances of insertions or deletions during replication Signup and view all the answers

Which type of repair mechanism is used to fix errors missed by DNA polymerase?

Mismatch repair Signup and view all the answers

What is the last-ditch repair mechanism used when other systems fail?

SOS repair Signup and view all the answers

Which method is used to isolate auxotrophs from a prototrophic parent strain?

Indirect selection Signup and view all the answers

Which type of mutation is the most common in aerobic environments?

Missense mutation Signup and view all the answers

What is the impact of adding or deleting three pairs of nucleotides in a DNA sequence?

Changes one codon and causes the addition or loss of one amino acid Signup and view all the answers

Which of the following describes the function of transposons?

They move from one location to another in the cell's genome Signup and view all the answers

Which of the following is an example of an induced mutation?

Chemical modification of nucleobases Signup and view all the answers

What is the most common type of mutation that occurs during DNA synthesis?

Base substitution Signup and view all the answers

Which of the following is true about the Ames test?

The Ames test measures the effect of chemicals on the reversion rate of histidine-requiring Salmonella auxotroph. Signup and view all the answers

Which of the following is NOT a mechanism of horizontal gene transfer?

Transcription Signup and view all the answers

What is the purpose of adding rat liver extract in the Ames test?

To convert non-carcinogenic chemicals to carcinogens Signup and view all the answers

What happens in bacterial transformation?

Naked DNA is taken up from the environment by a bacterial cell Signup and view all the answers

What did Griffith's experiment with Streptococcus pneumoniae demonstrate?

Living non-encapsulated cells can be transformed by DNA from heat-killed encapsulated cells Signup and view all the answers

Which of the following is NOT a method of gene transfer in bacteria?

Replication Signup and view all the answers

What is the main function of bacteriophages (phages) in gene transfer?

To attach to bacterial cells and inject their nucleic acid Signup and view all the answers

What is the result of generalized transduction?

Transfer of a fragment of bacterial DNA into the phage protein coat Signup and view all the answers

Which of the following is NOT a trait commonly found in plasmids?

Nitrogen fixation Signup and view all the answers

What is the main difference between conjugative plasmids and mobilizable plasmids?

Conjugative plasmids require a conjugative plasmid for transfer, while mobilizable plasmids do not Signup and view all the answers

Resistance to many medications can spread quickly

Resistance or R Plasmids Signup and view all the answers

Which of the following provides a mechanism for moving DNA?

Transposons Signup and view all the answers

Which of the following encode only the transposase enzyme and inverted repeats?

Transposons Signup and view all the answers

Which of the following are large DNA segments in a genome that originated in other species?

Genomic Islands Signup and view all the answers

Which of the following characteristics can be encoded by genomic islands?

Ability to cause disease Signup and view all the answers

Study Notes

Genetic Change and Gene Transfer

Barbara McClintock observed that kernel colors in corn were not inherited in a predictable manner, and she used the term "transposons" to describe the segments of DNA that moved in and out of genes involved in color.

Model Organism

The bacterium Escherichia coli (E. coli) is often used as a model system of genetic change.

Genetic Change Mechanisms in Bacteria

The two mechanisms of genetic change in bacteria are mutation and gene flow.

Publication of Research

The results of Barbara McClintock's research on kernel colors in corn were published in the 1950s.

Intercalating Agents

Intercalating agents, such as proflavin, are molecules that insert between adjacent bases in a DNA strand, causing frameshift mutations.

DNA Repair Mechanisms

The mismatch repair system is used to fix errors missed by DNA polymerase.
The SOS response is the last-ditch repair mechanism used when other systems fail.

Isolating Auxotrophs

Auxotrophs can be isolated from a prototrophic parent strain using penicillin.

Types of Mutations

Deletions or insertions of three pairs of nucleotides in a DNA sequence result in a frameshift mutation.
The most common type of mutation in aerobic environments is an oxidized guanine mutation.

Transposons

Transposons are segments of DNA that can move from one location to another within a genome, often causing mutations.
An example of an induced mutation is a mutation caused by exposure to ultraviolet (UV) light.

DNA Synthesis

The most common type of mutation that occurs during DNA synthesis is a point mutation.

The Ames Test

The Ames test is a method used to detect mutagenic chemicals, and it involves adding rat liver extract to the test system.
The purpose of adding rat liver extract is to simulate the metabolic activation of chemicals that occurs in the liver.

Gene Transfer in Bacteria

Bacterial transformation is the process by which free DNA is taken up by a bacterial cell, allowing for the exchange of genetic information.
Griffith's experiment with Streptococcus pneumoniae demonstrated the process of bacterial transformation.
Conjugation and transduction are mechanisms of horizontal gene transfer in bacteria.
Bacteriophages (phages) play a crucial role in gene transfer by serving as vectors for generalized transduction.

Plasmids and Transposons

Plasmids are small, self-replicating circular DNA molecules that can transfer genes between bacteria.
The main function of conjugative plasmids is to facilitate the transfer of genes between bacteria.
Mobilizable plasmids are transferred between bacteria through a process called conjugation.
The main difference between conjugative plasmids and mobilizable plasmids is that conjugative plasmids encode all the necessary genes for conjugation, whereas mobilizable plasmids do not.

Antibiotic Resistance

Horizontal gene transfer contributes to the spread of antibiotic resistance among bacteria.

Genomic Islands and Horizontal Gene Transfer

Genomic islands are large DNA segments in a genome that originated in other species.
Genomic islands can encode virulence factors, antibiotic resistance genes, and other traits that enhance the fitness of bacteria.
Horizontal gene transfer provides a mechanism for moving DNA between bacteria, allowing for the spread of antibiotic resistance and other traits.

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Description

This quiz covers topics related to selectively killing prototrophs, increasing auxotrophs, and the use of penicillin in cell growth. It also explores the screening process for potential carcinogens and their role in causing cancer. Test your knowledge on these important concepts!