Cell Division and Genetics Study Guide

Cell Cycle and Mitosis

• Interphase: Cell growth and DNA replication occur, consisting of G1, S, and G2 phases.
• M Phase (Mitosis): Division of the cell nucleus, consisting of prophase, metaphase, anaphase, and telophase.
• Cytokinesis: Division of the cytoplasm, resulting in two daughter cells.

Chromatin and Chromosomes

• Chromatin: Uncondensed form of DNA found during interphase.
• Chromosomes: Condensed form of DNA found during mitosis and meiosis.

Phases of Mitosis

• Prophase: Chromosomes condense, nuclear envelope breaks down.
• Metaphase: Chromosomes line up at the metaphase plate.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase: Nuclear envelopes reform, chromosomes decondense.

Asexual and Sexual Reproduction

• Asexual Reproduction: Rapid reproduction, less energy required, no need for a mate, but lacks genetic diversity.
• Sexual Reproduction: Increases genetic diversity, enhancing survival adaptability.

Mitosis vs. Meiosis

• Mitosis: Results in 2 identical diploid cells, used for growth and repair.
• Meiosis: Results in 4 non-identical haploid cells, used for sexual reproduction.

Genetic Diversity in Meiosis

• Steps increasing diversity:
  • Crossing Over: Exchange of genetic material between homologous chromosomes during prophase I.
  • Independent Assortment: Random distribution of homologous chromosomes during metaphase I.

Somatic Cells vs. Gametes

• Somatic cells: Body cells, diploid (2n), containing 46 chromosomes in humans.
• Gametes: Sex cells (sperm and eggs), haploid (n), containing 23 chromosomes in humans.

Homologous Chromosomes

• Definition: Pairs of chromosomes (one from each parent) that have the same structure and gene sequence but may contain different alleles.

Autosomes vs. Sex Chromosomes

• Autosomes: Non-sex chromosomes (22 pairs in humans).
• Sex Chromosomes: Determine biological sex (1 pair, X and Y in humans).

Chromosome Numbers

• Somatic cells: 46 chromosomes (diploid).
• Gametes: 23 chromosomes (haploid).

Genetics: Mendel and Heredity

• Vocabulary:
  • Homozygous: Two identical alleles (e.g., AA or aa).
  • Heterozygous: Two different alleles (e.g., Aa).
  • Trait: A characteristic.
  • Allele: A version of a gene.
  • Gene: A segment of DNA that codes for a trait.
  • Genotype: Genetic makeup.
  • Phenotype: Observable traits.
  • Genome: Complete set of genes.
  • Dominant: An allele that masks the effect of a recessive allele.
  • Recessive: An allele whose effects are masked by a dominant allele.

Genetic Crosses

• Dihybrid Cross:
  • Parents’ genotypes: RrBb x RRBB
  • Offspring genotypes: RRBb, RRBB, RrBb, RrBB
  • Offspring phenotypes: Normal running, black hair
• Multiple Alleles:
  • Parents: IBi x IAIB
  • Child’s probability: 50% blood type B (IBIB or IBi)
• Sex-Linked Traits:
  • Mother’s genotype: XHXh
  • Father’s genotype: XHY
  • Probability of non-hemophiliac child: 75%
  • Probability of affected child: 25%
  • Probability of hemophiliac egg producer: 0%

Theory of Evolution

• Geological Ideas of Darwin’s Time
• Contributors: Lyell...