Microbial genetics Flashcards
Define a gene
Segment of the genome that Codes for a specific protein, or stable RNA molecule
Define a chromosome
The overall structure of DNA within cells that control cellular activity. In prokaryotes the Chromosomes are circular.
Define a promoter
A sequence of DNA where RNA polymerase binds; to initiate transcription.
Define an operator
A DNA sequence to which a repressor protein may bind.
Define a codon
Groups of 3 nucleotide bases on mRNA. Each codon codes for an amino acid.
Define a mutation
A random change in the DNA sequence of the nucleotide bases.
Define a point mutation
A random change in the DNA sequence. Changing one nucleotide base for another.
Define a missense mutation
Caused by a point mutation; One amino acid is substituted for another.
Define a nonsense mutation
Caused by a point mutation; A premature STOP codon is introduced.
Define a frameshift mutation
Caused by an insertion or deletion mutation; A change in the translational reading frame
Define a silent mutation
Caused by a point mutation; There is no change in the amino acid sequence.
Define a mutagen
Agent that increases the mutation rate by 10 to 1000 times (Radiation or various chemicals)
Define a plasmid
Circular, extrachromosomal DNA molecules. Thought to give advantage over microbes without a plasmid. (Could code for genes for F factor pili, or R Factors, or Virulence factors)
Describe how strands of DNA are held together
The strands are held together by hydrogen bonds between based pairs (A-T, and C-G).
What is the backbone of DNA?
Sugar (Deoxyribose-phosphate)
What are the nucleotide bases of DNA?
Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
What is the role of the promoter sequence during transcription?
Binding site for RNA polymerase. Attrachs RNA polymerase to the gene so transcription can occur.
What is the product of transcription?
RNA
What is the product of translation?
Proteins
What is the product of DNA replication?
A new copy of DNA
What is the name of the enzyme that performs trancription?
RNA polymerase
What is the role of ribosomes during translation?
Forms the bonds between the amino acids during Translation. Building up the protein.
What is the role of mRNA during translation?
Acts as a blueprint that is read by the ribosome to build proteins.
What is the role of Codons during translation?
Codons code for amino acids, also tell the Ribosome when to start and stop protein synthesis.
Decribe the operon structure of gene regulation.
Composed of the control region (promoter, and operator), and the Structural genes.
What is the role of a repressor protein regulating gene expression?
Repressor protein are able to bind to the operator region of the operon, preventing RNA polymerase from reading the gene.
Describe how genes can be regulated based on the needs of the cell?
Repressor proteins can be activated or deactivated based on substrates present or not present. (For lac operon repressor gets deactivated when lactose is present. For Trp operon repressor gets activated when excess amounts of tryptophan is present.)
Decribe how a lac operon is regulated
For lac operon repressor gets deactivated when lactose is present.
Describe how a trp operon is regulated
Trp operon repressor gets activated when excess amounts of tryptophan is present.
What are the three mechanism that bacteria use for horizontal gene transfer?
Transformation, Conjugation, Transduction
Describe the flow of genetic information within a cell.
Transcription then Translation to proteins.
Describe the flow of genetic information of genetic information between generations of cells
Through Cellular replication, and passing copies of DNA to the daughter cells. (DNA replication)
Describe the flow of genetic information between cells of the same generation
Through mechanisms of horizontal gene transfer
What is the Enzyme that performs DNA replication?
DNA polymerase
What is the difference between gene and genome
A gene is a segment of the genome that codes for a specific protein. A geneom is a collection of all the genes.
What gets copied during DNA replication?
DNA
What gets read during Transcription?
DNA
What gets read during Translation?
mRNA
m in mRNA stands for what?
Messenger
When does transcription begin?
When RNA polymerase binds to the promoter sequence of a gene.
True or false: Is mRNA immediately ready for translation in prokaryotes?
True
Define constitutive proteins
Proteins that are expressed at a fixed rate. (genes are always on)
Define regulated proteins,
Proteins are expressed only as needed. (Genes can be turned on and off depending the cellular needs for the protein)
Define Repressible genes
Gene expression is normally on, but can be repressed. (if there are excess amounts of proteins.)
Define Inducible genes
Gene expression is normally off, but can be turned on (if the cell needs the protein in certain circumstances)
Define Structural genes
Genes that code for proteins. ( enzymes that work in a metabolic pathway)
What are the mechanisms for bacteria to acquire new genotypes?
Mutation, Plasmids, Transformation, Conjugation, Transduction
Why are mutations important for a population?
Mutations are necessary for adaptation and evolution. (Gives genetic variation)
Define spontaneous mutations
Occurs due to errors by DNA polymerase
Define vertical gene transfer
Transfer of genes that occurs during reproduction, between generations of cells.
Define horizontal gene transfer
Transfer of genes between cells of the same generation. 3 Mechanisms
Define transformation
Genes are transfered by DNA fragment being excreted into the environments. The DNA fragment is enveloped by another cell. The DNA fragment aligns with complementary bases of the original DNA, and recombination occurs between DNA fragment and original DNA.
Define Conjugation
A cell to cell transfer of plasmids through a pili. The Conjugating cells must be of opposite mating types. Donors F+, Recipients F-.
Define transduction
Bacterial DNA is transferred from a donor cell to a recipient cell inside a bacteriophage.
What is F factor?
A gene on a plasmid that could code for a pili allowing to transfer the plasmid itself.
What is R factors?
A gene on a plasmid that could code for antibiotic resistance.
What is virulence factors?
Encodes for factors that increase the pathogenicity of an organism? (Toxins)
What is the difference between a promoter and a start codon?
A promoter is on DNA and acts as binding site for RNA polymerase.
A start codon is on mRNA and signals to a ribosome that it should start translating and building the proteins.
