BIO BENCHMARK 2

Genetics & Heredity

Meiosis

  • A type of cell division that produces gametes (sperm and egg) with half the number of chromosomes.

  • Ensures genetic diversity through crossing over and independent assortment.

  • Outcome: Four genetically unique haploid cells.

Mendel’s Laws

  1. Law of Dominance: A dominant allele masks a recessive allele.

  2. Law of Independent Assortment: Genes for different traits assort independently during gamete formation.

  3. Law of Segregation: Each parent passes one allele to offspring.

Genetic Mutations & Variations

  • Sources of Genetic Variation:

    • New combinations from meiosis

    • Viable errors during replication

    • Mutations caused by environmental factors (radiation, chemicals, etc.)

  • Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to disorders like Down syndrome.

Probability & Variation in Traits

  • Punnett Squares: Predict possible genetic outcomes.

  • Genotypic vs. Phenotypic Ratios: Probability of inheriting traits.

  • Gene Flow: Movement of alleles between populations (e.g., migration).

  • Genetic Drift:

    • Founder Effect: A small group starts a new population.

    • Bottleneck Effect: Population size drastically decreases, reducing genetic diversity.

Evolution & Natural Selection

Evidence for Evolution

  • Homologous Structures: Same structure, different function (indicates common ancestry).

  • Analogous Structures: Different structure, same function (not from common ancestry).

  • Vestigial Structures: No longer used but inherited from ancestors (e.g., human appendix).

Natural Selection & Adaptation

  • Key Factors in Evolution:

    1. Potential for species to increase in number.

    2. Heritable genetic variation due to mutation and sexual reproduction.

    3. Competition for limited resources.

    4. Survival of organisms best suited for the environment.

  • Adaptation: Traits that enhance survival and reproduction become more common in a population.

Environmental Changes & Evolution

  • Changes in environment can:

    1. Increase numbers in some species.

    2. Cause the emergence of new species.

    3. Lead to extinction of others.

Cumulative Review Topics

DNA & Protein Synthesis (B-LS1-1)

  • DNA Structure: Double helix, made of nucleotides (A, T, C, G).

  • Transcription & Translation: DNA → mRNA → Protein.

Mitosis (B-LS1-4)

  • Purpose: Growth, repair, and asexual reproduction.

  • Outcome: Two identical diploid daughter cells.

Macromolecules (B-LS1-6)

  • Carbohydrates: Energy source.

  • Proteins: Structure, enzymes, transport.

  • Lipids: Long-term energy storage.

  • Nucleic Acids: Genetic information (DNA, RNA).