Bacterial Genetics Practice Flashcards

Flashcards covering bacterial genetics, gene transfer mechanisms, replication, transcription, translation, mutations, and DNA technology based on the lecture transcript.

Escherichia coli

One of the microorganisms established in the 1940s as a tool for studying genetics.

Neurospora crass

A microorganism used in the 1940s to study genetics, noted for its useful features such as short generation time.

Prokaryotic Genome

Usually circular, devoid of histones, and tightly coiled through supercoiling, with compact genetic information lacking introns and exons.

RNA polymerase recognition site (-35)

A specific site on the DNA template where RNA polymerase begins the process of recognition for transcription.

Shine dalgarno sequence

The leader gene sequence prior to the initiation codon $AUG$ that is recognized during the transcription process.

TTGACA

A protein subunit of RNA polymerase that binds to the promoter and initiates transcription.

TATAAT

A sequence that determines the precise location of the transcription start site where RNA polymerase binds.

Conjugation

A mechanism of gene transfer introduced by Joshua Lederberg (1945) requiring cell-to-cell contact via pili and energy in the form of $ATP$.

Transformation

The uptake of exogenous DNA, such as native bacterial chromosome fragments or plasmids, from the surrounding medium by a recipient cell.

Competence State

The ability of a bacterium to take up DNA from the medium, which can be natural or artificial.

Transduction

The transfer of genetic information between cells mediated by a virus or phage particle, introduced by Joshua Lederberg and Norton Zinder (1951).

Generalized Transduction

A type of transduction by phages $P1$ or $P22$ where only DNA of host origin is present in the particle.

purGA

A mnemonic used to identify the purine bases: Guanine and Adenine.

pyrCUT

A mnemonic used to identify the pyrimidine bases: Cytosine, Uracil, and Thymine.

mRNA

Messenger RNA, which makes up approximately $5\%$ of total RNA and carries information for translation.

rRNA

Ribosomal RNA, which makes up approximately $80\%$ of total RNA.

tRNA

Transfer RNA, which makes up approximately $15\%$ of total RNA and is involved in recognizing codons via anticodons.

Semi-conservative Replication

A theory of DNA replication where the daughter DNA contains one old strand and one new strand.

Helicase

An enzyme that separates the DNA helix template during the unwinding phase of replication.

DNA topoisomerase

An enzyme that relieves supercoiling in front of the replication fork to ensure smooth uncoiling.

DNA Polymerase I

An enzyme responsible for filling gaps left after the removal of RNA primers during DNA polymerization.

DNA Polymerase III

The primary enzyme responsible for polymerization, containing polypeptide alpha and an asymmetric dimmer.

Okazaki fragments

Short bursts of discontinuous DNA synthesis that occur on the lagging strand in the $5'$ to $3'$ direction.

Sigma factor

A component of bacterial RNA polymerase that guides the enzyme to the Shine dalgarno sequence to initiate transcription.

fmet

Formylated methionine, the first amino acid attached to the $30S$ sub-unit ribosome during translation initiation.

70S initiation complex

The functional bacterial ribosome formed by the binding of the $50S$ and $30S$ subunits.

Spontaneous Mutation

A mutation that occurs without known exposure to a mutagen, occurring at a rate of approximately $10^{-6}$ to $10^{-7}$ per gene per generation.

Transposons

Commonly known as jumping genes, these elements can move from one area of a DNA strand to another, causing variation.

Transition

A base substitution mutation where a base is replaced by another of the same chemical type (e.g., purine to purine).

Transversion

A base substitution mutation where a purine is replaced by a pyrimidine or vice versa.

Missense Mutation

A mutation that changes a codon for one amino acid into a codon for a different amino acid.

Nonsense Mutation

A mutation that changes an amino acid codon into a terminating codon ($UAG$, $UAA$, or $UGA$), resulting in premature chain termination.

Silent Mutation

A change in codon composition that has no effect on the resulting polypeptide because it codes for the same amino acid.

Frameshift Mutation

A mutation caused by the insertion or deletion of bases (non-multiples of 3) that shifts the reading phase of the genetic code.

Thymine dimer

A structural defect caused by Ultraviolet Light where two adjacent thymines bond to each other instead of their adenine partners.

AP site

An apurinic or apyrimidic site produced when the N-glycosylic bond connecting a base to the deoxyribose sugar is cleaved.

SOS Response

A last-resort DNA repair mechanism induced by DNA damage, regulated by the $RecA$ protein and $LexA$ repressor.

Plasmids

Closed circular or linear DNA molecules, sized between $2\,kb$ to $100\,kb$, that replicate independently of the bacterial chromosome.

Ames Test

A biological assay that uses mutant bacterial tester strains to determine the mutagenicity and potential carcinogenicity of a substance.

Bioremediation

The use of biological agents, such as genetically engineered bacteria, to degrade toxic environmental pollutants like oil spills.

Restriction Enzymes

Enzymes like $Eco\,R1$ that recognize specific palindromic nucleotide sequences and cleave DNA strands.