BIOL Mechanism In Evolution LEC 8

Announcements and Reminders

  • Assignments Due:

    • RRQ5 (Chapter 14): Due by 12 PM (noon) on Tuesday, February 18.

    • Module 4 assignment: Due by 11:59 PM next Thursday night, February 20.

  • Discussion Threads:

    • Post your thread in the Discussions tab in Biol 211 All Sections.

  • Office Hours:

    • Discuss your exam with instructor during office hours.

Seminar Series at California State University, Long Beach

  • Guest Speaker:

    • Kevin Alison, MS

    • Conservation Scientist, Native Plant Manager

    • Topic: Conservation through Cultivation: Advanced Propagation of Rare Plants

  • Biography:

    • Kevin Alison manages Native Plant species on Catalina Island to prevent extinction.

    • His work includes innovative propagation techniques like micropropagation and aeroponics for endangered plants.

  • Details:

    • Date: Thursday, February 13, 2025

    • Time: 4:00 - 4:50 PM

    • Zoom Meeting ID: 817 8028 2041

    • Contact: Dr. Houng-Wai Tsai (Houng-Wei.Tsai@csulb.edu)

Museum Collection Workshops

  • Specimen Preparation Workshop:

    • Learn to prepare museum specimens; registration required via email (kelly.hood@csulb.edu).

  • Schedule:

    • Birds Workshop: Friday, March 21, 9 AM - 1 PM.

    • Mammals Workshop: Friday, March 7, 9 AM - 1 PM.

    • Prerequisite: Completion of the Mammals workshop required to attend Birds workshop.

  • Cost: Workshops are free, materials provided.

Probability in Genetic Crosses

  • Gamete Production:

    • Probability of producing gametes carrying R or r is 0.5 for both parents.

    • Likelihood of fertilization with a r egg and r sperm:

      • 0.5 x 0.5 = 0.25.

  • Recessive Homozygote Probability:

    • Probability of obtaining rr in a monohybrid cross (Rr x Rr) is calculated similarly.

Calculating Genotype Probabilities

  • Heterozygote (Rr) Probability:

    • Two possible ways to get heterozygote: from mom or dad.

    • Total probability of obtaining heterozygote:

      • 0.25 + 0.25 = 0.5.

Dihybrid Cross Example

  • Dihybrid Cross (YyRr x YyRr):

    • Calculate probability of YYRr.

    • Use Punnett Square for visualization.

    • Result: Probability = 2/16 = 0.125.

  • Using Probability Rules for Calculation:

    • Treat alleles independently, calculate individual probabilities.

    • Combine probabilities of independent events for final genotype probability.

Understanding Genotype Affecting Phenotype

  • Genotype's Influence on Phenotype:

    • Mendel’s examples show qualitative variation.

    • Qualitative Traits:

      • Controlled by allelic variation at a single locus.

    • Population traits often follow bimodal distribution for two alleles.

Examples of Genotype and Phenotype

  • Flower Color Example:

    • Purple vs. White Flowers determined by allele at color locus.

  • Human Earwax Texture:

    • Wet (W) dominant over dry (w).

    • Genotype affects earwax phenotype (wet vs. dry).

Quantitative Variation

  • Many Traits Are Continuous:

    • Described as quantitative variation.

    • Human body height varies due to alleles at over 180 loci, presenting a normal distribution.

  • Polygenic Traits:

    • Result in continuous variation affecting phenotype and commonly represented graphically.

Evolution Overview

  • Evolution Definition:

    • Changes in allele frequencies in populations over time.

    • Requires genetic variation (more than one allele at a locus) for rates to change.

Sources of Genetic Variation

  • Genetic Variation Origins:

    • Mutations: Including point mutations, insertions, deletions, gene duplications.

    • Sexual Reproduction: Shuffling alleles through crossing over and independent assortment.

  • Mutations:

    • Can be neutral, harmful, or rarely beneficial.

    • Mutations do not arise based on organismal needs.

Hardy-Weinberg Equilibrium

  • Definition:

    • Non-evolving population where allele frequencies do not change.

  • Conditions for HW Equilibrium:

    1. No mutation.

    2. No gene flow.

    3. Very large population size.

    4. No natural selection.

    5. Random mating.

  • Importance of HW Equilibrium:

    • Identifies cases of evolution by measuring deviations from model predictions.

Essential Vocabulary

  • Key Terms:

    • Qualitative Variation, Quantitative Variation, Polygenic Traits, Gene Pool, Allele Frequency, Genotype Frequency, Hardy-Weinberg Equation.

Study Questions

  1. Define evolution.

  2. Where does genetic variation come from?

  3. Are mutations generally beneficial, neutral, or harmful?

  4. Do mutations arise in response to needs or randomly?

  5. Max number of alleles at a locus in diploid individuals versus a population?

  6. Calculate allele and genotype frequencies when given population data.

  7. Can two populations have the same allele frequencies but different genotype frequencies?

  8. Use Hardy-Weinberg to identify evolution in action.

  9. Conditions for HW equilibrium.