SB

10_Lecture_Presentation

Introduction to Viruses and Genetics

  • Measles caused by a contagious virus, identifiable by a red rash.

  • The virus was almost eradicated in the U.S. until a 2014 outbreak.

  • Understanding of DNA and RNA is crucial in combating viruses.

Big Ideas in Molecular Biology

  • The Structure of Genetic Material

  • DNA Replication

  • Flow of Genetic Information: DNA → RNA → Protein

  • Genetics of Viruses and Bacteria

The Structure of Genetic Material

Experiments Demonstrating DNA as Genetic Material

  • Early 20th century: The basis for inheritance was unclear.

  • Frederick Griffith's Experiment (1928):

    • Mixed dead pathogenic bacteria with live harmless bacteria.

    • Result: Some harmless bacteria became pathogenic, inheriting this trait.

  • Hershey and Chase Experiment:

    • Used phages (bacterial viruses) to show DNA, not protein, is the genetic material.

    • Phage DNA directed the host cell to produce more phages.

DNA and RNA Polymers

  • Nucleic Acids (DNA/RNA): Long chains of nucleotides.

  • Nucleotide Structure:

    • Nitrogenous base, five-carbon sugar, phosphate group.

  • DNA vs RNA:

    • DNA: Uses deoxyribose, bases include A, C, T, G.

    • RNA: Uses ribose, base uracil (U) instead of thymine (T).

The Double Helix Structure of DNA

  • Watson and Crick discovered DNA is a double-stranded helix.

  • Base pairing:

    • A with T

    • G with C

  • The structure allows for the storage and replication of genetic information.

  • Nobel Prize awarded in 1962 to Watson, Crick, and Wilkins.

  • Rosalind Franklin's contributions are acknowledged posthumously.

DNA Replication

Process of DNA Replication

  • Begins with separation of DNA strands.

  • Enzymes create complementary strands using each original strand as a template.

  • Semiconservative Model:

    • Each new helix has one old strand and one new strand.

Visual Representation of DNA Replication

  • Parental DNA molecules serve as templates for new daughter strands.

  • Results in two identical DNA molecules.

Flow of Genetic Information

From DNA to Protein

  • Genes (sequences of DNA) are transcribed into RNA, then translated into proteins.

  • Transcription: DNA → RNA synthesis.

  • Translation: RNA → Proteins synthesis.

Codons and Genetic Code

  • Codons: Triplet code that corresponds to amino acids.

  • The same genetic code is used across nearly all organisms.

Mutations and Their Effects

  • Mutations: Changes in genetic information due to DNA replication errors or environmental factors.

  • Effects vary based on nucleotides substituted, inserted, or deleted.

Genetics of Viruses and Bacteria

Viruses

  • Viral Structure:

    • Consist of nucleic acids (DNA/RNA) encased in a protein coat (capsid).

  • Lytic Cycle: Virus replicates its DNA, assembles new virions, bursts host cell.

  • Lysogenic Cycle: Viral DNA integrates into host chromosome, replicates with host cell's DNA, remains dormant.

Emerging Viruses

  • Emerging viruses can quickly become significant health threats (e.g., HIV, Coronavirus).

  • Understanding of genetic principles critical for response.

Summary of Key Experiments

  • Griffith, Hershey, and Chase's experiments all support that DNA is the genetic material.

  • Structural differences between DNA and RNA are crucial for understanding their functions.

  • The DNA structure enables effective replication essential for heredity.