AP BIOLOGY | UNIT V - Heredity

key concepts and vocabulary for this unit

Meiosis

Key Question: How does this process differ from Mitosis?

• MITOSIS: creation of two genetically identical and diploid daughter cells

• MEIOSIS: creation of four genetically unique and haploid gametes [sex cells used for reproduction]

Meiosis: the process of creating gametes with variation for reproduction

• Meiosis I: Homologous Chromosomes

  • Prophase I: chromatin condenses, sister chromatids/homologous chromosomes align

    • Crossing Over: when alleles are exchanged between homologous pairs from each parent to increase variation and diversity

  • Metaphase I: HOMOLOGUS CHROMOSOMES align and independently assort

  • Anaphase I: HOMOLOGOUS CHROMOSOMES will separate and move to opposite poles of the cell

  • Telophase I and Cytokinesis: the cell splits, and two haploid cells are created

• Meiosis II: Sister Chromatids

  • Prophase II

  • Metaphase II: SISTER CHROMATIDS align at the metaphase plate

  • Anaphase II: SISTER CHROMATIDS will separate and move to opposite poles of the cell

  • Telophase II and Cytokinesis: the cell splits, and two haploid cells are created

What is the difference? | Homologous Pairs v. Sister Chromatids

Homologous Pairs are chromosomes that are similar but are from different parents; crossing over occurs between these pairs for variations.

THINK! That is why you look like a mix of both your parents.

Sister Chromatids are identical copies of a chromosome (typical “x” formation seen in diagrams)

Inheritance Patterns

1. Complete Dominance: Dominant (AA) and Heterozygous (Aa) genotypes look the same, Mandel’s pattern of inheritance

2. Incomplete Dominance: a blending of the traits from each parent

   • ex. red flower and white flower breed to create a pink flower

3. Codominance: the presence of both parents’ traits in the offspring

   • ex. a red and white flower breeding to create an offspring with both red and white petals

4. Autosomal Inheritance: inheritance with traits located on autosomal genes [non-sex-determining genes]

5. Sex-Linked Inheritance: inheritance with traits located on the sex genes

6. Maternal Inheritance: inheritance linked to mitochondria and/or chloroplasts

Punnett Squares and Pedigrees

Punnett Square: a visual method that allows you to calculate the probability of a genotype

• Monohybrid Crosses focus on one singular trait

• Dihybrid Crosses focus on two traits

Pedigrees: family trees that show the inheritance pattern of a certain trait, can help you determine the genotype of an individual based on lineage