In this episode, we focus on DNA mutations and repair, a key topic for the Bio/Biochem section of the MCAT. We'll cover the different types of mutations, including point mutations, insertions, and deletions, and explain how they occur due to replication errors or environmental factors like UV radiation.

You'll also learn about the repair mechanisms that fix these genetic changes, such as direct reversal, mismatch repair, and base excision repair. We’ll also discuss how double-strand breaks are addressed through homologous recombination and non-homologous end joining.

By the end of this episode, you'll gain a thorough understanding of how mutations happen and the processes the body uses to repair them, helping you prepare for related MCAT questions.

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(00:00) Intro

(01:07) Overview of DNA Mutations and Repair

(01:45) What is a Mutation?

(02:30) Mutations During DNA Replication

(03:29) DNA Polymerase Slippage: Causes duplication of repeated sequences in DNA

(06:15) Mutations Before or After Replication: Caused by mutagens like radiation or chemicals

(07:19) Mutagens vs. Carcinogens: Differences between agents that cause mutations and those that cause cancer

(09:56) Types of Mutations: Overview of point mutations, insertions, and deletions

(12:00) Frameshift Mutations: How insertions or deletions shift the reading frame

(29:50) Chromosomal Mutations: Inversions and translocations

(35:35) DNA Repair Mechanisms: Introduction to replication repair, mutation repair, and break repair

(36:51) Proofreading by DNA Polymerase: Repairing replication errors

(39:20) Direct Reversal DNA Repair: Enzymes directly fix damaged DNA

(40:41) Mismatch Repair: Fixing base mismatches and insertion-deletion loops

(43:25) Base Excision Repair: Correcting single-base mutations

(46:03) Nucleotide Excision Repair: Fixing bulky DNA damage like pyrimidine dimers

(47:56) Interstrand Cross-Link Repair: Repairing DNA strands covalently cross-linked together

(50:27) Single-Strand Break Repair: Ligating broken DNA strands back together

(51:16) Double-Strand Break Repair: Homologous recombination and non-homologous end joining

(54:13) Summary of DNA repair mechanisms

DNA Mutations and Repair

MCAT Basics (from MedSchoolCoach)