Chapter12 - part 1

The Genetic Material

  • Early Experiments (1900s)

    • Established that deoxyribonucleic acid (DNA) is the genetic material of all living organisms.

    • Key Pages: 208 – 212 (12th edition)

    • Figures: 12.1 (p. 208), 12.2 (p. 209)

Molecular Structure of DNA

  • Understanding DNA (1950s-1960s)

    • Significant contributions from scientists: Chargaff, Franklin, Watson, and Crick.

    • Key Pages: 208 – 212 (12th edition)

    • Figure: 12.4 (p. 211)

Components of DNA

  • Structure of DNA

    • DNA is a polymer made of nucleotides.

    • Each nucleotide consists of:

      • 5-carbon sugar

      • Phosphate group

      • Nitrogen-containing base (adenine, thymine, guanine, or cytosine).

    • Key Pages: 208 – 212 (12th edition)

    • Figure: 12.3 (p. 210)

DNA Double Helix

  • Structure

    • DNA forms a double-helix shape due to:

      • Complementary base pairing (A = T and G = C).

      • Antiparallel strand orientation.

    • Key Pages: 208 – 212 (12th edition)

    • Figure: 12.5 (p. 210)

DNA Replication

Overview

  • Process

    • Takes place during the S stage of interphase.

    • Semiconservative Replication: Each daughter double helix consists of one old strand and one new strand (old strand serves as template).

    • Key Pages: 213 - 215 (12th edition)

    • Figure: 12.6 (p. 213)

Step 1: Unwinding

  • Role of DNA Helicase

    • Unwinds the DNA strands to provide a template for replication.

Step 2: Base Pairing

  • Role of DNA Polymerase

    • Complements base pairing with existing strands.

    • DNA primase synthesizes a primer first.

    • Leading strand is continuous, while the lagging strand is made in Okazaki fragments.

    • Key Pages: 213 - 215 (12th edition)

    • Figures: 12.6 (p. 213), 12.7 (p. 214)

Step 3: Joining Fragments

  • Role of DNA Ligase

    • Joins Okazaki fragments on the lagging strand to create a continuous strand.

    • Key Pages: 213 - 215 (12th edition)

    • Figure: 12.7 (p. 214)

RNA Structure and Function

  • Comparison to DNA

    • RNA is single-stranded and contains uracil instead of thymine.

    • Types of RNA:

      1. Messenger RNA (mRNA)

      2. Transfer RNA (tRNA)

      3. Ribosomal RNA (rRNA)

    • Key Pages: 215 - 217 (12th edition)

    • Table: 12.2 (p. 215)

    • Figure: 12.9 (p. 216)

Central Dogma of Molecular Biology

  • Using DNA to Build Proteins

    • Two main processes:

      1. Transcription: RNA strand is synthesized from a DNA template.

      2. Translation: Ribosomes read the RNA to synthesize proteins.

    • Key Pages: 215 - 217 (12th edition)

    • Figure: 12.10 (p. 216)

Genetic Code

  • Basis of the Code

    • Composed of triplet codons (three nucleotides).

    • Each codon corresponds to a specific amino acid, forming proteins.

    • Key Pages: 215 - 217 (12th edition)

    • Figure: 12.11 (p. 217)