Ch.7: Microbial Genetics Flashcards
What is a plasmid?
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.
What are the types of plasmids?
- Fertility (F) Plasmid
- Resistance (R) Plasmid
- Virulence Plasmid
What is the primary function of mRNA?
Carries genetic information from chromosome to ribosome
What is the role of tRNA?
Carries amino acids to the ribosome
What type of RNA is part of the ribosome?
rRNA
What is the central dogma of genetics?
Information in DNA is copied to RNA, and polypeptides are synthesized from RNA
What is an operon?
A promoter, series of genes, and adjacent regulatory element (operator) in prokaryotes
What is a mutation?
A change in nucleotide base sequence of a gene
What are the three types of point mutations?
- Silent
- Missense
- Nonsense
What is a mutagen?
Physical or chemical agents that induce a mutation
What are the two types of radiation mutagens?
- Ionizing Radiation (IR)
- Non-ionizing Radiation (UV)
What is the significance of thymine dimers?
They are the most common types of mutations caused by UV radiation
What is horizontal gene transfer?
Donor contributes DNA to a recipient
What are the three methods of horizontal gene transfer?
- Transformation
- Transduction
- Conjugation
What is the function of the F plasmid?
Contains instructions for the formation of conjugation pili
What is the Ames test used for?
To help identify a carcinogen
What is a competent cell?
A cell that takes up DNA from the environment due to alterations in the cell wall or plasma membrane
What does a repressible operon do?
Always transcribed until deactivated by a repressor that inhibits transcription
What activates an inducible operon?
The presence of an inducer
What is a wild-type organism?
The most commonly found genotype/phenotype in nature
What is Nonsense mutation
type of mutation typically results in a non-functional protein
Fill in the blank: Mutations in a population must be ________, _______, and ________.
Deleterious, lasting, inheritable
What is the role of gyrase and topoisomerase in DNA replication?
They remove supercoils in DNA to prevent tangling
What is the typical mutation frequency in genes?
1 in every 10 million (10^7) genes contain a mutation
What is the difference in mRNA usage between prokaryotes and eukaryotes?
Prokaryotes – 1 mRNA = many polypeptides; Eukaryotes – 1 mRNA = 1 polypeptide
What is the effect of chemical mutagens on nucleotides?
They alter a nucleotide’s structure, causing base pair substitutions
What happens during the termination stage of translation?
Occurs when a stop codon is encountered and no complementary tRNA exists
True or False: All genes in bacteria are always expressed.
False
What is the role of quorum sensing in bacteria?
To produce pathogenic proteins only when reaching a sufficient population density
What is the difference between inducible and repressible operons?
Inducible operons are activated by an inducer; repressible operons are always active until inhibited
What is transduction?
transfer DNA through a virus
-occurs in prokaryotes and eukaryotes
what is a bacteriophage?
A virus that infects and lyses bacteria
What is transformation?
Takes up DNA from the environment
What is an Auxotroph
mutant with different nutritional requirements than wild-type
what is a mutant
mutation that has been passed to progeny
what is a silent mutation?
no change in phenotype
what is a missense mutation?
change amino acid sequence; can result in non-functional proteins or no change
What is a nonsense mutation?
early termination of protein synthesis
What is an inducible operon?
-Genes that are not usually transcribed
-involved in catabolic pathways whole polypeptides are not needed until the nutrient is available
What is initiation in translation?
Prokaryotes-formylmethionine (AUG)
Eukaryote-methionine (AUG)
What is Translation?
the process in which ribosomes use genetic information of nucleotide sequences (mRNA) to synthesize polypeptides
What is a genome
entire genetic complement and nucleotide sequences that connect genes to one another
-Genomes of cell or DNA viruses=DNA
-RNA viruses=RNA
In genome what do prokaryotes and Eukaryotes use?
-Prokaryotes use chromosomes or plasmids
-Eukaryotes use nuclear and extranuclear DNA
Describe Chromosomes in prokaryotic genomes.
-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
