Molecular Biology Mock Exam Flashcards

This flashcard set covers key concepts from a Molecular Biology mock exam, including DNA replication, transcription, translation, and DNA repair mechanisms in E. coli.

Griffith

The scientist who originally discovered the process of bacterial transformation.

Hershey and Chase

Scientists who concluded that DNA functions as the genetic material based on experiments with $T2$ bacteriophages.

Phenotype of $PpTt$

The observable characteristics of purple flowers and tall plants, where $P$ (purple) and $T$ (tall) are dominant alleles.

Okazaki fragment

A segment of DNA that acts as an intermediate in the synthesis of the lagging strand.

DNA ligase

An enzyme that is not required for the initiation of DNA replication in E. coli.

$5' \text{-} 3'$ exonuclease activity (DNA Polymerase I)

An activity of E. coli DNA polymerase I involved in the removal of RNA primers by nick translation.

Beta ($\beta$) subunit (DNA Polymerase III)

A subunit of prokaryotic DNA polymerase III that acts as a circular clamp to improve the processivity of DNA synthesis.

Sigma ($\text{σ}$) factor

A factor required by the E. coli RNA polymerase core enzyme to selectively bind promoter regions and initiate synthesis.

Transcription Initiation Sequence

The order of events involving closed complex formation, open complex formation, start of RNA synthesis, and finally promoter clearance.

Rho-terminator

An ATP-dependent RNA-DNA helicase in E. coli that causes RNA polymerase release at a CA-rich sequence.

Max Polypeptide Molecular Weight (800 Nucleotides)

The largest polypeptide coded by a $800$ nucleotide mRNA is approximately $30,000$, assuming an average amino acid residue weight of $110$.

Wobble Hypothesis

A hypothesis stating that the "wobble" occurs only in the first base of the anticodon.

tRNA Structure

A single-stranded RNA molecule containing several short double-helical regions and an amino acid attachment at an $A$ nucleotide at the $3'$ end.

Ribosomal Initiation Complex

A complex in bacterial protein synthesis that requires formylmethionyl tRNA $fMet$, $IF-2$, and mRNA, but does not require $EF-Tu$.

Peptidyl transferase

A ribozyme that catalyzes the elongation phase of protein synthesis.

Housekeeping genes

Bacterial genes expressed constitutively at varying levels because their promoters have different affinities for RNA polymerase holoenzyme.

Promoter Consensus Sequence

A sequence that many E. coli promoters resemble which has the highest affinity for RNA polymerase holoenzyme.

trp operon attenuation

A regulatory mechanism that is decreased when selected bases in sequence $3$ of the leader peptide are mutated.

Tryptophan repressor

A protein that represses the tryptophan operon of E. coli by binding to the trp operator specifically in the presence of tryptophan.

CRP (cAMP receptor protein)

A protein that assists RNA polymerase binding to the lac promoter in E. coli.

DNA glycosylase

An enzyme that is not directly involved in methyl-directed mismatch repair in E. coli.

ABC excinuclease

An enzyme essential for nucleotide-excision repair.

Ames test

A procedure used to measure the mutagenic effects of various chemical compounds.

Direct repair

A specific mechanism used to repair thymidine dimers in DNA.