Ch.7: Microbial Genetics

Question 1

What is a plasmid?

Answer 1

Small, extrachromosomal, circular DNA that replicates independently of the chromosome ONLY in prokaryotes!!

Plasmids are usually not essential for bacterial metabolism, growth, or reproduction but can confer advantages.

Question 2

What are the types of plasmids?

Answer 2

• Fertility (F) Plasmid
• Resistance (R) Plasmid
• Virulence Plasmid

Question 3

What is the primary function of mRNA?

Answer 3

Carries genetic information from chromosome to ribosome

Question 4

What is the role of tRNA?

Answer 4

Carries amino acids to the ribosome

Question 5

What type of RNA is part of the ribosome?

Answer 5

rRNA

Question 6

What is the central dogma of genetics?

Answer 6

Information in DNA is copied to RNA, and polypeptides are synthesized from RNA

Question 7

What is an operon?

Answer 7

A promoter, series of genes, and adjacent regulatory element (operator) in prokaryotes

Question 8

What is a mutation?

Answer 8

A change in nucleotide base sequence of a gene

Question 9

What are the three types of point mutations?

Answer 9

• Silent
• Missense
• Nonsense

Question 10

What is a mutagen?

Answer 10

Physical or chemical agents that induce a mutation

Question 11

What are the two types of radiation mutagens?

Answer 11

• Ionizing Radiation (IR)
• Non-ionizing Radiation (UV)

Question 12

What is the significance of thymine dimers?

Answer 12

They are the most common types of mutations caused by UV radiation

Question 13

What is horizontal gene transfer?

Answer 13

Donor contributes DNA to a recipient

Question 14

What are the three methods of horizontal gene transfer?

Answer 14

• Transformation
• Transduction
• Conjugation

Question 15

What is the function of the F plasmid?

Answer 15

Contains instructions for the formation of conjugation pili

Question 16

What is the Ames test used for?

Answer 16

To help identify a carcinogen

Question 17

What is a competent cell?

Answer 17

A cell that takes up DNA from the environment due to alterations in the cell wall or plasma membrane

Question 18

What does a repressible operon do?

Answer 18

Always transcribed until deactivated by a repressor that inhibits transcription

Question 19

What activates an inducible operon?

Answer 19

The presence of an inducer

Question 20

What is a wild-type organism?

Answer 20

The most commonly found genotype/phenotype in nature

Question 21

What is Nonsense mutation

Answer 21

type of mutation typically results in a non-functional protein

Question 22

Fill in the blank: Mutations in a population must be ________, _______, and ________.

Answer 22

Deleterious, lasting, inheritable

Question 23

What is the role of gyrase and topoisomerase in DNA replication?

Answer 23

They remove supercoils in DNA to prevent tangling

Question 24

What is the typical mutation frequency in genes?

Answer 24

1 in every 10 million (10^7) genes contain a mutation

Question 25

What is the difference in mRNA usage between prokaryotes and eukaryotes?

Answer 25

Prokaryotes – 1 mRNA = many polypeptides; Eukaryotes – 1 mRNA = 1 polypeptide

Question 26

What is the effect of chemical mutagens on nucleotides?

Answer 26

They alter a nucleotide's structure, causing base pair substitutions

Question 27

What happens during the termination stage of translation?

Answer 27

Occurs when a stop codon is encountered and no complementary tRNA exists

Question 28

True or False: All genes in bacteria are always expressed.

Answer 28

False

Question 29

What is the role of quorum sensing in bacteria?

Answer 29

To produce pathogenic proteins only when reaching a sufficient population density

Question 30

What is the difference between inducible and repressible operons?

Answer 30

Inducible operons are activated by an inducer; repressible operons are always active until inhibited

Question 31

What is transduction?

Answer 31

transfer DNA through a virus -occurs in prokaryotes and eukaryotes

Question 32

what is a bacteriophage?

Answer 32

A virus that infects and lyses bacteria

Question 33

What is transformation?

Answer 33

Takes up DNA from the environment

Question 34

What is an Auxotroph

Answer 34

mutant with different nutritional requirements than wild-type

Question 35

what is a mutant

Answer 35

mutation that has been passed to progeny

Question 36

what is a silent mutation?

Answer 36

no change in phenotype

Question 37

what is a missense mutation?

Answer 37

change amino acid sequence; can result in non-functional proteins or no change

Question 38

What is a nonsense mutation?

Answer 38

early termination of protein synthesis

Question 39

What is an inducible operon?

Answer 39

-Genes that are not usually transcribed -involved in catabolic pathways whole polypeptides are not needed until the nutrient is available

Question 40

What is initiation in translation?

Answer 40

Prokaryotes-formylmethionine (AUG) Eukaryote-methionine (AUG)

Question 41

What is Translation?

Answer 41

the process in which ribosomes use genetic information of nucleotide sequences (mRNA) to synthesize polypeptides

Question 42

What is a genome

Answer 42

entire genetic complement and nucleotide sequences that connect genes to one another -Genomes of cell or DNA viruses=DNA -RNA viruses=RNA

Question 43

In genome what do prokaryotes and Eukaryotes use?

Answer 43

-Prokaryotes use chromosomes or plasmids -Eukaryotes use nuclear and extranuclear DNA

Question 44

Describe Chromosomes in prokaryotic genomes.

Answer 44

-Bacteria and Archaea -package DNA with necessary proteins and RNA into one or two chromosomes only one copy (haploid) only Archaea have histones Located in nucleoid