Microbiology Chapter 8 Study Guide

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Questions and Answers

Genetic change in bacteria can be brought about by which of the following?

Conjugation (correct)

Mutation (correct)

Transduction (correct)

Transformation (correct)

How is the damage caused by ultra-violet light to DNA best described?

Thymine bases on 1 strand of DNA, next to each other, are covalently linked together to form a thymine dimer.

How is DNA constructed?

Two strands of nucleotides running in an antiparallel configuration.

DNA replication proceeds in only 1 direction around the bacterial chromosome.

True Signup and view all the answers

Bacteria usually contain multiple chromosomes.

False Signup and view all the answers

In the context of DNA repair, what competes with an endonuclease?

Methylase Signup and view all the answers

What is an enzyme produced in response to the presence of a substrate called?

Inducible enzyme. Signup and view all the answers

Cell-to-cell contact is required for transduction to occur.

False Signup and view all the answers

What stops the synthesis of a repressible enzyme?

Corepressor-repressor complex binding to the operator. Signup and view all the answers

What allows different cells to produce different proteins?

miRNAs in a cell. Signup and view all the answers

What enzyme catalyzes the cutting and resealing of DNA?

Transposase. Signup and view all the answers

How does conjugation differ from reproduction?

Conjugation transfers DNA horizontally to nearby cells without those cells undergoing replication. Signup and view all the answers

How is a gene defined?

A sequence of nucleotides in DNA that codes for a functional product. Signup and view all the answers

Recombination will always alter a cell's genotype.

True Signup and view all the answers

What is genetics?

The study of genes, how they carry information, how information is expressed, and how genes are replicated. Signup and view all the answers

What are chromosomes?

Structures containing DNA that physically carry hereditary information. Signup and view all the answers

What are genes?

Segments of DNA that encode functional products, usually proteins. Signup and view all the answers

What is a genome?

All the genetic information in a cell at a given time. Signup and view all the answers

What is genotype?

The genetic makeup of an organism. Signup and view all the answers

What is phenotype?

Expression of the genes. Signup and view all the answers

What are exons?

Regions of DNA that code for proteins. Signup and view all the answers

What are introns?

Regions of DNA that do not code for proteins. Signup and view all the answers

What is a mutation?

A permanent change in the base sequence of DNA. Signup and view all the answers

What is a mutagen?

Agents that cause mutations. Signup and view all the answers

What is the Central Dogma?

DNA -> RNA -> Protein. Signup and view all the answers

Discuss how DNA serves as genetic information.

The structure of DNA helps explain 2 primary features: the linear sequence of bases provides the information, and the complementary structure allows for precise duplication during cell division. Signup and view all the answers

What are DNA forms?

A double helix with a deoxyribose-phosphate backbone. Signup and view all the answers

What happens during DNA replication?

DNA polymerase adds nucleotides to the growing DNA strand in the 5' to 3' direction, initiated by an RNA primer. Signup and view all the answers

What is protein synthesis?

The formation of proteins using information contained in DNA and carried by mRNA. Signup and view all the answers

What is transcription?

The organic process where the DNA sequence in a gene is copied into mRNA. Signup and view all the answers

What is RNA processing?

The modification of mRNA before it leaves the nucleus, unique to eukaryotes. Signup and view all the answers

What is translation?

Decoding of an mRNA message into a polypeptide chain. Signup and view all the answers

Compare protein synthesis in prokaryotes and eukaryotes.

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What is pre-transcriptional control?

Repression inhibits gene expression and decreases enzyme synthesis; induction turns on gene expression. Signup and view all the answers

What is post-transcriptional control?

Riboswitch and microRNAs (miRNAs). Signup and view all the answers

What are mutations?

A permanent change in the base sequence of DNA that may be neutral, beneficial or harmful. Signup and view all the answers

What is mutation repair?

Signup and view all the answers

What are mutagen effects?

Increase the mutation rate to per $10^{-5}$ or $10^{-3}$ replicated gene. Signup and view all the answers

What are mutation rates?

Spontaneous mutation rate is 1 in $10^9$ replicated base pairs or 1 in $10^6$ replicated genes. Signup and view all the answers

Outline the methods of direct and indirect selection of mutants.

Positive (direct) selection detects mutant cells because they grow or appear different than unmutated cells; negative (indirect) detects mutant cells that cannot grow or perform a certain function. Signup and view all the answers

Discuss the functions of plasmids and transposons.

Plasmids carry genes for sex pili, catabolism, and antibiotic resistance. Transposons move within and between DNA regions. Signup and view all the answers

Compare and contrast horizontal and vertical gene transfer.

Vertical gene transfer occurs during reproduction; horizontal gene transfer occurs between cells of the same generation. Signup and view all the answers

Compare and contrast the mechanisms of genetic recombination in bacteria.

Vertical gene transfer occurs during reproduction while horizontal gene transfer includes transformation, conjugation, and transduction. Signup and view all the answers

Study Notes

Genetic Change in Bacteria

Genetic changes can occur through transformation, mutation, conjugation, and transduction.
Transformation involves uptake of "naked" DNA from the environment.
Conjugation requires direct cell-to-cell contact and is a form of horizontal gene transfer.
Transduction transfers bacterial DNA via bacteriophage.

UV-Induced DNA Damage

UV light causes thymine dimers, where adjacent thymine bases on DNA strands covalently bond.

Structure of DNA

DNA consists of two antiparallel nucleotide strands forming a double helix.
The backbone is made of deoxyribose and phosphate groups, with hydrogen bonds between A-T and C-G pairs.

DNA Replication

DNA replication occurs in one direction on the bacterial chromosome.
DNA polymerase synthesizes the new strand, using RNA primers and adding nucleotides in the 5' to 3' direction.
The leading strand is synthesized continuously, while the lagging strand forms Okazaki fragments.

Types of Enzymes and DNA Repair

Inducible enzymes are produced in response to specific substrates.
Repair processes may involve a race between endonuclease and methylase.
Mutation is a permanent alteration in DNA sequence while mutagens are agents causing mutations.

Gene Definitions and Functions

A gene is a nucleotide sequence that codes for a functional product.
Genetics encompasses the study of gene information, expression, and replication.
The genome contains all genetic information in a cell at any time.

Genotype vs. Phenotype

Genotype refers to the organism's genetic makeup, while phenotype is the observable expression of genes.

Exons and Introns

Exons are DNA regions coding for proteins, while introns are non-coding regions.

Central Dogma of Molecular Biology

The flow of genetic information is described as DNA → RNA → Protein.

Protein Synthesis Process

Transcription copies DNA into mRNA, which is then modified in eukaryotes before translation into proteins.

Gene Regulation

Pre-transcriptional control includes repression (inhibiting expression) and induction (activating expression).
Post-transcriptional control involves mechanisms such as riboswitches and microRNAs to regulate gene expression.

Mutation and Repair

Mutations can have neutral, beneficial, or harmful effects and occur spontaneously at rates of 1 in 10^9 for base pairs.
Mutation repair can involve several mechanisms depending on the type of mutation.

Selection Methods for Mutants

Direct (positive) selection identifies mutants by their growth or appearance, while indirect (negative) selection identifies mutants that lack certain functions.

Plasmids and Transposons

Plasmids can carry traits like antibiotic resistance and enzymes for unique compound metabolism.
Transposons can move DNA segments within a genome and include sequences for cutting and resealing DNA.

Gene Transfer Mechanisms

Vertical gene transfer involves inheritance between generations, while horizontal gene transfer occurs between cells of the same generation.
Transformation, conjugation, and transduction are key mechanisms of horizontal gene transfer, each with unique processes.

Recombination in Bacteria

Transformation involves uptake of naked DNA; conjugation requires direct contact; and transduction involves DNA transfer via bacteriophages.

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Description

This quiz covers key concepts from Chapter 8 of your microbiology study material. You'll explore genetic changes in bacteria and the effects of UV light on DNA. Prepare to test your understanding of transformations, mutations, and more.