Molecular Biology

🏥 Molecular Biology

Part 1 of 7 — DNA Replication

Replication is semiconservative: each new DNA molecule has one old and one new strand.

Helicase unwinds, primase lays RNA primer, DNA pol III extends 5-to-3, ligase seals gaps.

Concept Check 🎯

Key Insight: Leading strand: continuous synthesis; Lagging strand: Okazaki fragments.

MCAT Tip: Telomerase extends telomeres in germ cells and stem cells — prevents chromosome shortening.

Concept Check 🎯

Fill in the Blanks 🔍

Transcription & RNA Processing

Part 2 of 7 — Transcription & RNA Processing

Transcription: RNA polymerase reads template 3-to-5, synthesizes mRNA 5-to-3.

Promoter: TATA box ~25 bp upstream; transcription factors help RNA pol II bind.

Concept Check 🎯

Key Insight: Post-transcriptional processing: 5-cap (7-methylguanosine), 3-poly-A tail, intron splicing.

MCAT Tip: Alternative splicing: one gene can produce multiple mRNA variants and thus multiple proteins.

Concept Check 🎯

Fill in the Blanks 🔍

Translation & Protein Synthesis

Part 3 of 7 — Translation & Protein Synthesis

Ribosome: small subunit reads mRNA; large subunit catalyzes peptide bond formation.

Start codon AUG (methionine) initiates translation; 3 stop codons: UAA, UAG, UGA.

Concept Check 🎯

Key Insight: tRNA anticodon pairs with mRNA codon; aminoacyl-tRNA synthetase charges tRNA with correct amino acid.

MCAT Tip: Post-translational modifications: phosphorylation, glycosylation, ubiquitination, proteolytic cleavage.

Concept Check 🎯

Fill in the Blanks 🔍

Gene Regulation

Part 4 of 7 — Gene Regulation

Operon model (prokaryotes): lac operon (inducible), trp operon (repressible).

Eukaryotic regulation: enhancers, silencers, transcription factors, chromatin remodeling.

Concept Check 🎯

Key Insight: Epigenetics: DNA methylation silences genes; histone acetylation activates genes.

MCAT Tip: miRNA and siRNA: small RNAs that silence gene expression post-transcriptionally.

Concept Check 🎯

Fill in the Blanks 🔍

Mutations & Repair

Part 5 of 7 — Mutations & Repair

Point mutations: silent, missense, nonsense, frameshift (insertion/deletion).

Missense: different amino acid; Nonsense: premature stop codon; Silent: same amino acid.

Concept Check 🎯

Key Insight: DNA repair: mismatch repair, base excision repair, nucleotide excision repair.

MCAT Tip: Mutagens: UV light (thymine dimers), chemicals (alkylating agents), radiation (double-strand breaks).

Concept Check 🎯

Fill in the Blanks 🔍

Biotechnology & Lab Techniques

Part 6 of 7 — Biotechnology & Lab Techniques

PCR: amplifies specific DNA sequences using primers, Taq polymerase, and thermal cycling.

Gel electrophoresis: separates DNA/protein by size; smaller fragments migrate faster.

Concept Check 🎯

Key Insight: CRISPR-Cas9: gene editing using guide RNA to target specific sequences.

MCAT Tip: Southern blot (DNA), Northern blot (RNA), Western blot (protein) — remember SNOWdrop.

Concept Check 🎯

Fill in the Blanks 🔍

Review & MCAT Practice

Part 7 of 7 — Review & MCAT Practice

PCR: amplifies specific DNA sequences using primers, Taq polymerase, and thermal cycling.

Gel electrophoresis: separates DNA/protein by size; smaller fragments migrate faster.

Concept Check 🎯

Key Insight: CRISPR-Cas9: gene editing using guide RNA to target specific sequences.

MCAT Tip: Southern blot (DNA), Northern blot (RNA), Western blot (protein) — remember SNOWdrop.

Concept Check 🎯

Fill in the Blanks 🔍