Lecture5.1_2025

Page 1: Introduction

• Title: Life: The Science of Biology (Twelfth Edition)

• Authors: Hillis, Heller, Hacker, Hall, Laskowski, Sadava.

• Focus: Chapter 13 discusses DNA and its role in heredity.

Page 2: Image Attribution

• Source: Photo is licensed under CC BY-SA-NC from Science Source.

Page 3: Study Unit Overview

• Unit: Study Unit 4 focuses on the Cell Cycle.

• Phases:

  • G1: Cell growth and preparation for DNA replication.

  • S Phase: DNA replication.

  • G2: Further growth and preparation for mitosis.

  • M Phase: Division of the cell (mitosis).

Page 4: S Phase Function

• Question: What is the function of the S phase?

  • A. Growth and preparation for DNA replication

  • B. Separation of sister chromatids (DNA division)

  • C. Splitting of the cell (cytokinesis)

  • D. DNA copying (DNA replication)

  • E. Preparation for DNA division

Page 5: Key Concepts of Chapter 13

1. Experiments Revealed the Function of DNA as Genetic Material

2. DNA Structure Fits Its Function

3. DNA Replication is Semiconservative

4. DNA Errors can be Repaired

5. Polymerase Chain Reaction (PCR) Amplifies DNA

Page 6-7: Key Concepts Recap

• Reiteration of Key Concepts for emphasis on the significance of DNA in biology and heredity.

Page 8: DNA Structure Insights

• Evidence for DNA Structure:

  • Chemical Studies: DNA as a polymer of nucleotides.

  • Base Composition: Variations among organisms.

  • X-ray Diffraction: Helped discern the helical structure.

  • Watson-Crick Model: Established the double helix configuration.

• Features: 10 base pairs per complete turn.

Page 9: Visual Representation

• Figure 13.6: DNA as a double helix, 3.4 nm between bases, consistent width of 2 nm.

Page 10: DNA Backbone Structure

• Strand Composition:

  • Phosphate Group: Attaches to carbon atoms in the sugar.

  • 5' and 3' Ends: Directionality of the DNA strand’s backbone.

  • Base Pairing: Attaches to the 1' carbon of the sugar.

Page 11: Bases of DNA

• Four Bases in DNA:

  • Adenine (A)

  • Cytosine (C)

  • Guanine (G)

  • Thymine (T)

Page 12: Purines and Pyrimidines

• Purines (2 Ring Structures):

  • Adenine (A)

  • Guanine (G)

• Pyrimidines (1 Ring Structures):

  • Cytosine (C)

  • Thymine (T)

Page 13: Drawing DNA

• Illustration: Visual representation of DNA structure concepts.

Page 14: DNA Structure Question

• Query: How many turns in a DNA with 10,000 bases?

  • A. 500 turns

  • B. 1,000 turns

  • C. 5,000 turns

  • D. 10,000 turns

  • E. Cannot be determined

Page 15: Complementary DNA Strand

• Question: Complementary sequence for strand 5'-AGCTGCTGA-3'?

  • A. 5'-AGCTGCTGA-3'

  • B. 3'-AGCTGCTGA-5'

  • C. 5'-TCGACGACT-3'

  • D. 3'-TCGATGACT-5'

  • E. 5'-TCAGCAGCT-3'

Page 16: Phosphodiester Bonds Query

• InDNA with 5'-AGCTGCTGAA-3': Number of phosphodiester bonds?

Page 17: Hydrogen Bonds Query

• In the same DNA strand: Number of hydrogen bonds present?

Page 18: DNA Double Helix Functionality

• Importance of DNA Structure:

  • Nucleotide Arrangement: Encodes genetic information.

  • Mutation Susceptibility: Suggests how small changes can have big effects.

  • Complementary Base Pairing: Ensures accurate replication.

  • Phenotype Expression: Genetic info is reflected in traits.

  • Amino Acid Sequences: Determine protein structure and function.

Page 19: Homework Assignment

• Task: Complete the replication bubble diagram with labels on relevant structures.