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).