Slides

Meiosis & Mendelian Genetics

Learning Goals

  • Understand how genetic information is passed to offspring through sexual reproduction.

Key Terms

  • Gene: A segment of DNA influencing phenotypes.

  • Allele: A specific form of a gene with distinct DNA sequences.

  • Genotype: The genetic constitution of an individual.

  • Phenotype: Observable characteristics resulting from genotype.

  • Homozygosity: Having two identical alleles for a given gene.

  • Heterozygosity: Having two different alleles for a given gene.

Meiosis Overview

  • Stages of Meiosis: Diagram the sequence of events from DNA replication through to chromosome segregation:

    • Meiosis I: Homologous chromosomes separate.

    • Meiosis II: Sister chromatids separate, producing four haploid gametes.

  • Meiosis vs. Mitosis:

    • Mitosis results in two identical diploid daughter cells.

    • Meiosis results in four genetically diverse haploid gametes.

Genetic Variations

  • Nondisjunction:

    • Failure of homologous chromosomes or sister chromatids to separate during meiosis, leading to gametes with abnormal chromosome numbers.

Mendel’s Principles

  • Principle of Segregation: Alleles segregate independently into gametes.

  • Calculate the probability of specific gametes when assuming independent segregation.

Chromosomes and Karyotypes

  • Examine homologous chromosomes and sister chromatids in a human karyotype.

  • Identify the differences in terms based on chromosome pairings.

Key Concepts on Traits

  • Phenotypes: Examples from Scottish Fold cats:

    • Straight Ear Trait vs. Folded Ear Trait.

    • Different genotypes evident in the TRPV4 allele affecting these traits.

Genetic Experiments with TRPV4

  • Experimentation with wildtype and mutant TRPV4 to study the effects on calcium concentrations in cells:

    • Increased calcium leads to folded ear traits, indicating phenotypic effects from mutations.

Genetic Relationships in Offspring

  • When crossing a homozygous straight-eared cat with a homozygous folded-eared cat, all offspring exhibited the folded ear trait, showing dominance.

  • When breeding heterozygous folded ear cats, offspring ratios are predicted through Mendelian genetics.

Inheritance Patterns and Genetic Linkage

Week 2 Goals

  • Study Mendel’s principle of independent assortment and how it increases genetic variation during meiosis.

  • Understand multi-gene inheritance patterns and calculate probabilities of genotypes in offspring.

Genetic Linkage Overview

  • Genes closer together on chromosomes may assort together and lead to inheritance patterns differing from Mendelian predictions.

Speciation

  • Describe how speciation can occur over generations due to reproductive isolation and genetic divergence between populations.

Mechanisms of Evolution

  • Natural Selection: Differential survival causing allele frequency changes over generations.

  • Habitat fragmentation: Impacts on species interactions and biodiversity through metapopulation dynamics.

Species Interactions

  • Competition: Interspecific competition can lead to coexistence or competitive exclusion. Both negatively impact involved species.

  • Mutualism: Positive interactions where both species benefit, as seen with mycorrhizal fungi and plants.

Biodiversity and Ecosystems

  • Ecosystem services depend on biodiversity and the balance of species interactions within ecosystems.

  • Human Impact on Biodiversity: Over-exploitation, habitat loss, and climate change threaten ecosystem stability.

Climate Change Effects

  • Shifts in ecosystems and species distributions due to changing climates, affecting phenology and species interactions.