Microbiology test 3

hiphip hooray

The study of inheritance and inheritable traits expressed in an organism's genetic material.

genetics

genome

The entire genetic complement of an organism (bacteria, eukaryote, virus).

What is a gene

A segment of DNA that codes for a functional product (a protein or regulation site).

chromosome in bacteria?

Genes essential for survival, typically circular and most bacteria have one (haploid).

plasmid

Extra chromosomal DNA found in some organisms that replicates independently and is not essential for normal bacterial metabolism, growth, or reproduction.

structure of nucleic acids

WHAT (structure) are polymers made of repeating units of nucleotides (monomers).

components of nucleotides

WHAT (components) are made of nitrogenous bases and complementary base pairs.

structure of DNA.

WHAT is double stranded with complementary strands running antiparallel (5'-3' and 3'-5').

Hydrogen bonds between DNA bases

WHAT bonds form between the bases, while covalent bonds form between the sugar and phosphate sides.

RNA compared to DNA

RNA is single-stranded, composed of ribose sugar, and substitutes uracil for thymine.

process of DNA replication

Bacteria replicate their DNA as the first step in binary fission, using a semiconservative model where each strand serves as a template.

role of helicase in DNA replication

WHAT unwinds DNA and creates a replication fork.

Okazaki fragments

Short, newly synthesized DNA fragments formed on the lagging strand during DNA replication.

function of DNA ligase

_____ ______ seals gaps between Okazaki fragments.

central dogma of genetics

The process of gene expression where DNA is transcribed to mRNA, which is then translated to produce proteins.

three steps of transcription

Initiation, elongation, and termination.

EIT

transcription

The product of __________ is mRNA.

DNA template during transcription

WHAT is unwound and used to synthesize mRNA in TRANSCRIPTION

Is the mRNA code universal

Yes, the mRNA code is universal and used by all organisms.

role of mRNA in gene expression

_____ carries transcribed information from DNA to the ribosomes for protein synthesis.

function of ribosomal RNA (rRNA)

_____ is part of ribosomes and catalyzes protein synthesis.

What does transfer RNA (tRNA) do

____ transfers amino acids to the ribosomes, where proteins are synthesized.

codon

WHAT is a 3-base sequence of nucleotides in mRNA that codes for an amino acid.

three stages of translation

Initiation, Elongation, and Termination.

initiation stage of translation

The mRNA, tRNA, and ribosome come together at the start codon.

elongation stage of translation

Codon recognition, peptide bond formation, and translocation occur.

What triggers termination in translation

The ribosome reaches a stop codon, leading to the release of the polypeptide.

operon

WHAT is a group of genes that work together, regulated as a single unit.

repressible operon

a WHAT is usually transcribed (on) and must be turned off by an active repressor protein (e.g., Trp Operon).

inducible operon

An WHAT is usually not transcribed (off) and must be turned on by a molecule that inactivates the repressor (e.g., Lac Operon).

promoter in an operon function

WHAT is the DNA segment where RNA polymerase attaches to begin transcription.

role of the operator in an operon

The WHAT is the DNA segment where the repressor protein binds to block transcription.

tryptophan function in the trp operon

WHAT acts as a co-repressor that activates the repressor, turning off its own production.

lac operon when lactose is absent

The WHAT is active, switching the lac operon off.

lac operon when lactose is present

The repressor is inactivated, allowing the lac operon to be turned on.

product of translation

The WHAT is a polypeptide (protein).

significance of the start codon

The WHAT (AUG) signals the beginning of translation.

significance of stop codons

WHAT (UAG, UAA, UGA) signal the termination of translation.

structure of tRNA

WHAT is a short piece of folded RNA containing 3 loops, with an anticodon and an acceptor stem for an amino acid.

role of the regulatory gene in an operon

The WHAT codes for a repressor protein that controls the operon's transcription.

function of the repressor protein

The WHAT blocks RNA polymerase from initiating transcription.

How operons conserve energy in prokaryotes

By regulating gene expression, operons prevent unnecessary transcription and conserve resources.

relationship between transcription and translation

Transcription produces mRNA from DNA, which is then translated into proteins at the ribosomes.

role of the release factor in termination

The WHAT binds to the stop codon, causing hydrolysis and the release of the polypeptide.

function of the acceptor stem in tRNA

The WHAT is where a specific amino acid is attached to the tRNA molecule.

significance of the 5' and 3' ends of mRNA

They indicate the directionality of the mRNA strand, which is important for translation.

mutation

A permanent change in the nucleotide base sequence of a genome.

point mutations

Mutations where a single base in the DNA sequence is inserted, deleted, or substituted.

Frameshift mutation

A mutation caused by an insertion or deletion that shifts the reading frame of the genetic code.

frequency of mutation in DNA replication

About 1 mutation per 1 billion DNA replications.

mutagens

Agents that increase mutation rates, including environmental factors like radiation and chemicals.

two types of radiation mutagens

Ionizing radiation (X rays and gamma rays) and nonionizing radiation (UV rays).

nucleotide analogs

Chemical mutagens that mimic DNA or RNA nucleotides and can be incorporated into DNA during replication.

positive selection in identifying mutants

Selecting mutants by eliminating wild types, allowing only mutants to grow.

negative selection in identifying mutants

Selecting mutants by identifying auxotrophs, which require different nutrients than wild types.

horizontal gene transfer

The exchange of genes between bacteria of the same generation, resulting in recombinant cells.

The three methods of genetic recombination

Transformation, transduction, and conjugation.

transformation in bacteria

The transfer of DNA fragments from the environment into a bacterial cell.

Limitation of transformation

The recipient bacterium must be competent to take up DNA from its environment.

transduction

Genetic transfer mediated through a bacteriophage that infects bacteria.

Limitation of transduction

It requires a bacteriophage to infect the bacteria.

Bacterial conjugation

The transfer of DNA from one bacterium to another through direct cell-to-cell contact via a pilus.

F plasmid

A fertility plasmid that contains genes necessary for the formation of a pilus in bacterial conjugation.

What happens in F+ x F- conjugation

The F+ donor bacterium transfers its F plasmid to the F- recipient, converting it to F+.

Hfr conjugation

A process where an Hfr donor bacterium transfers part of its chromosome to an F- recipient, but not the entire F plasmid.

auxotroph

A mutant that has a nutrient requirement different from that of the wild type.

role of a pilus in bacterial conjugation

It facilitates the transfer of DNA between donor and recipient bacteria.

significance of Griffith's experiments

They demonstrated the process of transformation in bacteria using rough and smooth strains.

effects of point mutations

They can lead to silent, nonsense, or frameshift mutations, affecting protein synthesis.

outcome of Hfr x F- conjugation

The recipient bacterium gains new DNA but remains F- and does not receive the entire F plasmid.