AP Bio Unit 5 (Ch 7 and 8) Genetics Slides

Unit 5: Genetics

Overview

• Definition: Genetics is the study of heredity, genes, and variations in living organisms.

Meiosis and Mitosis

Mitosis

• Definition: A process of cell division that results in two genetically identical daughter cells.

• Key Points:

  • Chromosomes duplicate into sister chromatids.

  • These sister chromatids are distributed to two daughter cells.

  • Produces somatic (body) cells.

  • Diploid (2N) cells produce diploid (2N) daughter cells.

Meiosis

• Definition: A specialized form of cell division that produces four genetically distinct haploid (N) daughter cells.

• Key Points:

  • Chromosomes duplicate, then homologous chromosomes line up and segregate.

  • Produces gametes (sperm and egg).

  • Diploid (2N) cells undergo reduction to haploid (N) cells.

Chromosomal Structure

• Chromosomes: Cellular structures made of DNA and protein;

  • Homologous Chromosomes: Similar DNA, same genes but different alleles.

  • Sister Chromatids: Duplicated chromosomes connected at the centromere.

Diploid vs. Haploid

• Haploid (N): Cells with one copy of each chromosome.

• Diploid (2N): Cells with two copies of each chromosome.

• Example: Human somatic cells are 2N = 46; gametes are N = 23.

Meiosis I vs. Mitosis

• One main difference:

  • Meiosis I: homologous chromosomes separate.

  • Mitosis: sister chromatids separate.

• Both involve phases: Prophase, Metaphase, Anaphase, and Telophase.

Oogenesis

• Process: Formation of egg cells.

• Key Points:

  • Uneven division during cytokinesis results in 3 polar bodies and 1 mature ovum.

  • Polar bodies cannot usually fertilize; they play a role in providing resources to the mature egg.

Fertilization Process

• Stages:

  1. Sperm contacts egg, reacts with zona pellucida.

  2. Acrosomal reaction occurs, allowing the sperm nucleus to enter the egg.

  3. Cortical granules prevent entry of other sperm.

Important Definitions in Genetics

1. Genotype: Genetic makeup of an organism (allele combination).

2. Phenotype: Observable traits of an organism.

3. Allele: Different forms of a gene.

4. Punnett Square: Diagram used to predict the outcome of a genetic cross.

5. Heterozygous: Pair of different alleles.

6. Homozygous: Pair of identical alleles.

Mendelian Genetics

• Gregor Mendel: Father of Genetics; used pea plants for his experiments.

• Key Principles:

  • Law of Segregation: Alleles for a trait segregate during gamete formation.

  • Law of Independent Assortment: Traits are inherited independently.

Mendel's Pea Plant Traits:

• Seed shape: Round vs. Wrinkled

• Seed color: Yellow vs. Green

• Flower color: Purple vs. White

Non-Mendelian Inheritance

1. Incomplete Dominance: Intermediate phenotype (e.g., red + white = pink).

2. Codominance: Both alleles expressed (e.g., AB blood type).

3. Multiple Alleles: More than two allele forms (e.g., rabbit coat color).

4. Polygenic Traits: Traits controlled by multiple genes (e.g., height, skin color).

5. Pleiotropy: One gene affects multiple traits.

6. Environmental Influence: Environmental conditions affect gene expression.

Genetic Disorders

• Nondisjunction: Failure of chromosomes to separate during meiosis, leading to disorders like:

  • Down Syndrome: Three copies of chromosome 21.

  • Turner Syndrome: Female with one X chromosome.

  • Klinefelter Syndrome: Male with an extra X chromosome.

Chromosomal Comparisons

• Karyotype: An image showing the complete set of chromosomes.

• Sex chromosomes: Determine biological sex (e.g., XX for females, XY for males).

• Autosomes: Remaining chromosomes that do not determine sex.

Pedigrees and Inheritance Patterns

1. Autosomal Dominant: Trait appears in every generation, affects both sexes equally.

2. Autosomal Recessive: Unaffected parents can have affected children; affects both sexes equally.

3. Sex-linked Recessive: Affects males more; females need two copies of the affected allele.

Non-Nuclear Inheritance

• Some cellular DNA is found in organelles like mitochondria and chloroplasts, inherited maternally.

Unit 5: Genetics OverviewDefinition: Genetics is the study of heredity, genes, and variations in living organisms.

Key Concepts:

• Meiosis and Mitosis:

  • Mitosis: Cell division resulting in two identical daughter cells; involves duplication of chromosomes.

  • Meiosis: Specialized division producing four genetically distinct haploid cells; reduces chromosome number from diploid to haploid.

• Chromosomal Structure:

  • Chromosomes: DNA and protein structures.

  • Homologous Chromosomes: Same genes, different alleles.

  • Sister Chromatids: Duplicated chromosomes together at the centromere.

• Genetics Terminology:

  • Genotype: Organism's genetic makeup.

  • Phenotype: Observable traits.

  • Allele: Variations of a gene.

Key Principles of Inheritance:

• Mendelian Genetics: Law of Segregation and Law of Independent Assortment discovered by Gregor Mendel.

• Non-Mendelian Inheritance: Incomplete dominance, codominance, multiple alleles, polygenic traits, and environmental influences.

Genetic Disorders:**

• Nondisjunction: Results in disorders like Down Syndrome, Turner Syndrome, and Klinefelter Syndrome.

Inheritance Patterns:**

• Pedigrees: Used to track inheritance; includes autosomal dominant, autosomal recessive, and sex-linked traits.