Cheat Sheet 8: Molecular Genetics

DNA Replication

Copying genetic information in cells.

Leading Strand

Synthesized continuously during DNA replication.

Lagging Strand

Synthesized discontinuously with Okazaki fragments.

Okazaki Fragments

Short nucleotide stretches formed on lagging strand.

DNA Polymerase III

Enzyme synthesizing new DNA in 5' to 3' direction.

Helicase

Unzips DNA double helix into single strands.

RNA Primer

Initial RNA segment for DNA synthesis initiation.

Primase

Enzyme creating RNA primer for DNA replication.

Ligase

Seals gaps between Okazaki fragments.

Topoisomerase

Relieves stress from unwinding DNA strands.

Telomere

DNA segment protecting chromosome ends from degradation.

Telomerase

Enzyme adding telomeres to chromosome ends.

mRNA

Messenger RNA for protein synthesis.

tRNA

Transfers amino acids to mRNA codons.

rRNA

Forms part of ribosomes for protein synthesis.

Transcription

Synthesizing RNA from a DNA template.

RNA Splicing

Removing introns and reconnecting exons in mRNA.

Exons

Protein-coding regions of the genome.

Introns

Non-coding regions in pre-mRNA.

Translation

Synthesis of proteins from mRNA sequence.

Point Mutation

Single nucleotide change causing substitution, insertion, or deletion.

Frameshift Mutation

Shifts reading frame of RNA transcript.

Silent Mutation

Codon change does not alter amino acid.

Missense Mutation

New codon encodes a different amino acid.

Nonsense Mutation

Codon change results in a premature stop codon.

Wild Type

mRNA sequence without any mutation.

Plasmids

Small, circular DNA molecules in bacteria.

Lac Operon

Operon for lactose processing in prokaryotes.

Trp Operon

Operon for tryptophan synthesis in prokaryotes.

Operons

Gene clusters controlling transcription in prokaryotes.

Conjugation

DNA transfer via cell-to-cell contact in bacteria. Pilus (bridge) between bacteria is formed

Transformation

Uptake of free DNA from surroundings by a competent bacterium.

Transduction

DNA transfer via bacteriophage infection. EX: Virus that infects bacteria.

Genome

Complete genetic information of an organism.

Transcriptome

All RNA molecules produced by a cell.

Proteome

Complete set of expressed proteins in an organism.

Post-transcriptional processing

Adding 5' cap to 5' end and poly-A tail to 3' end of mRNA for stability

Initiation

1st step in transcription: RNA polymerase attaches to promoter region and unzips DNA into 2 strands

Elongation

2nd step in transcription: RNA polymerase synthesizes RNA nucleotides using one DNA strand as template

Termination

3rd step in transcription: RNA polymerase reaches a special sequence, detaches from DNA, and disassembles from complex