Learning Objectives

  • Mutations
    • Define mutation: A change in the nucleotide sequence of DNA.
    • Identify two types of mutagens:
    • Spontaneous mutations: Random errors in DNA replication with no external cause.
    • Induced mutations: Changes caused by external factors, e.g., chemicals, radiation.
    • Define and differentiate:
    • Substitutions: One nucleotide is replaced by another.
    • Insertions: An extra nucleotide is added to the sequence.
    • Deletions: A nucleotide is removed from the sequence.
    • Explain the effects of substitutions, insertions, and deletions on amino acid sequences.
    • Differentiate and define:
    • Silent mutations: Do not change the amino acid sequence.
    • Missense mutations: Change one amino acid in the sequence.
    • Nonsense mutations: Result in a premature stop codon, truncating the protein.

Mutation Definition

  • Mutation: A change in the nucleotide sequence within DNA.
  • Spontaneous mutations: Random errors that occur during DNA replication.
    • Example: A sequence change from TACC GGC TGG AA to TACC GGC TAG AA.

Effects of Mutations on DNA

  • Induced mutations: Result from exposure to chemicals or radiation.
    • Example: A sequence change from TACC GGC TGG AA to TACC GGC TTT AA.
  • Group activity: Analyze how mutations affect mRNA and amino acid sequences.

Types of Mutations

  • Substitution: One letter replaced by another.
    • Example: TACC to TACC can change the amino acid sequence.
  • Insertion: One letter added to the sequence can shift reading frames.
  • Deletion: Removal of one letter can also shift reading frames.

Repairing Mutations

  • Mutations can often be repaired; thus, the change may not be passed on to daughter cells.
  • Changes may alter the effectiveness of proteins, impacting genetic diseases.
  • Genetic diversity: Beneficial mutations can increase resilience to environmental changes.

Genetics Overview

  • Genetics: The study of inheritance patterns passed from one generation to another.
  • Gametes: Cells (sperm & egg) used in reproduction that combine to create offspring.

Mendel's Experiments

  • Gregor Mendel's plant hybridization experiments led to fundamental discoveries in genetics.
  • True-breeding plants: Plants that produce offspring identical to the parent.

Mendel's Crosses

  • P Generation: True-breeding parents (e.g., purple and white flowers).
    • F1 Generation: All offspring exhibit the dominant trait (purple).
    • F2 Generation: Predicted ratios observed (705 purple to 224 white).

Alleles and Traits

  • Alleles: Various forms of a gene that determine traits (e.g., flower color).
    • Dominant alleles mask the expression of recessive alleles.
  • Phenotypes: Observable traits resulting from genotypes (BB, Bb for brown eyes).

Punnett Square Overview

  • A Punnett square is a diagram used to predict genetic outcomes of a cross.
    • Helps visualize the probability of offspring traits based on parental alleles.
  • Ratios:
    • E.g., 25% homozygous dominant, 50% heterozygous, 25% homozygous recessive.
    • Phenotype ratios derived from F2 generation predictions (e.g., 75% pink, 25% white).