Molecular Biology Processes

Flashcards covering key terms and processes related to DNA replication, transcription, translation, gene regulation, mutations, DNA repair, and post-transcriptional modifications.

DNA Polymerase III

Main enzyme that adds nucleotides in the 5′ to 3′ direction during DNA replication in prokaryotes.

DNA Polymerase I

Enzyme that removes RNA primers and replaces them with DNA, possessing 5′ to 3′ exonuclease activity.

Leading Strand

Strand that is synthesized continuously towards the replication fork during DNA replication.

Lagging Strand

Strand that is synthesized discontinuously, producing Okazaki fragments during DNA replication.

Helicase

Enzyme that unwinds the DNA double helix during replication.

Primase

Enzyme that lays down RNA primers for DNA synthesis.

Topoisomerase

Enzyme that relieves the supercoiling ahead of the replication fork.

Ligase

Enzyme that seals nicks between Okazaki fragments in DNA.

RNA Polymerase I

Enzyme that synthesizes ribosomal RNA (rRNA), except for 5S rRNA.

RNA Polymerase II

Enzyme responsible for synthesizing messenger RNA (mRNA).

RNA Polymerase III

Enzyme that synthesizes transfer RNA (tRNA), other small RNAs, and 5S rRNA.

Sigma Factor

Protein that helps prokaryotic RNA polymerase recognize the promoter region for transcription initiation.

TFIID

Transcription factor that binds to the TATA box in eukaryotic gene transcription initiation.

Alternative Splicing

Process that allows for the production of multiple mRNAs and proteins from a single gene.

Peptidyl Transferase

Ribosomal enzyme that catalyzes peptide bond formation during translation.

Enhancers

Regulatory sequences that increase transcription levels from a significant distance.

Operators

Binding sites for repressors in prokaryotic gene regulation.

SOS Response

Damage-induced repair system in prokaryotes, regulated by RecA and LexA.

Silent Mutation

Mutation that does not result in a change in the amino acid sequence.

Missense Mutation

Mutation that results in the change of one amino acid to another.

Nonsense Mutation

Mutation that creates a premature stop codon in the coding sequence.

Frameshift Mutation

Mutation caused by insertions or deletions that alter the reading frame of the gene.

Base Excision Repair (BER)

DNA repair mechanism that removes damaged bases and replaces them.

Nucleotide Excision Repair (NER)

DNA repair mechanism that removes bulky DNA lesions such as thymine dimers.

Mismatch Repair (MMR)

Repair mechanism that detects and corrects mismatched bases during DNA replication.

Homologous Recombination

DNA repair process that uses a homologous sequence as a template.

RecA

Protein that facilitates strand invasion during prokaryotic homologous recombination.

Non-Homologous End Joining (NHEJ)

DNA repair mechanism that ligates broken DNA ends without the need for homologous templates.

5′ Capping

Modification that adds a 7-methylguanosine cap to the 5′ end of eukaryotic mRNA for stability and translation initiation.

Polyadenylation

Addition of a Poly-A tail to the 3′ end of eukaryotic mRNA for stability.

Ribozyme

Catalytic RNA molecule capable of acting like an enzyme, such as peptidyl transferase.

Post-Transcriptional Modifications

Changes that occur to RNA molecules after transcription, including capping, tailing, and splicing.