Ch15 Mutations and Population Genetics

Dropbox Submissions

• Students can submit assignments at specified times:
• Today, Wednesday, and Friday deadlines mentioned for submissions.
• Important to submit on time to avoid loss of points.

Multiple Choice Exam

• Closes tonight at 11:59 PM; reminders given to complete it.
• If missed, communicate for extensions before answers are released.

Course Evaluations

• Students encouraged to complete evaluations.
• Aim for 80% class completion to unlock a bonus question on the final exam.

Practical Exam

• Scheduled for Monday afternoon.
• Review held last Monday; practice practicals to assess readiness.

Chapter Review: Mutations

• Continuing from previous discussion in Chapter 15 on mutations.
• Mutation defined as a heritable change in the DNA sequence without indicating if it's good or bad.

Types of Mutations

• Base Substitutions: Mutations at a single spot in the DNA.

  • Silent Mutation:
  • Codon changes, but the amino acid remains the same (e.g., changing CTT to CTC still encodes leucine).
  • The wobble position is often where these changes occur without affecting the amino acid.

• Missense Mutation:

• Results in a different amino acid, changing the primary structure of the polypeptide.

• Can be categorized as:

  • Conservative Missense: Similar properties (e.g., arginine to lysine).
  • Nonconservative Missense: Different properties (e.g., lysine to glutamate).

• Nonsense Mutation:

• New codon becomes a stop codon, leading to truncated polypeptides.

• Any mutations at critical positions can impact function significantly.

Effect of Insertions and Deletions

• Insertion/Deletion Mutations: Add or lose nucleotides.
• Effects depend on the number of nucleotides affected.
• Frame Shift Mutation: Non-multiple of three nucleotides added/deleted, changing the entire reading frame and affecting all downstream codons.
• Non-Frame Shift Mutations: Multiples of three, maintaining reading frame but potentially affecting the immediate codon.

Mutation Severity Ranking

• Most Severe:
• Nonsense > Frame Shift
• Less Chance of Functionality in proteins.
• Missense and silent have less severe impacts, with silent being the least severe.

Mutation Location and Effects

• Mutations can happen in coding sequences or regulatory sequences, affecting gene expression.
• Polar Mutations: Affect downstream genes in operons.
• Promoter Mutations: Can block transcription entirely.

Mutation Rates and Frequencies

• Mutation Rate: Likelihood of mutation in a gene per generation (ranges from 10^{-5} to 10^{-9}).
• Influenced by organism type, gene length, sequence, and environmental factors.
• Mutation Frequency: How common a mutation is in a population.
• Affected by selection processes (beneficial mutations increase frequency, harmful mutations decrease).

Gene Pool and Population Genetics

• Population genetics focuses on groups, studying gene frequency changes over time.
• Polymorphic vs. Monomorphic Genes:
• Polymorphic genes have multiple alleles, indicating genetic health.
• Monomorphic genes are ignored as they contribute no variation.

Genotype Frequency Calculation:

• Calculation based on observed genotypes in a population (e.g., frequency of recessive alleles).
• Important for understanding genetic diversity in populations.

Hardy-Weinberg Principle

• Used to relate allelic frequencies and genotype frequencies under equilibrium conditions.
• Plans to modify Hardy-Weinberg application to include real-world factors (migration, selection) discussed for the final chapter study.