Unit 3 ALL NOTES

Chapter 16: Cell Division

Overview

• All living organisms are composed of cells.

• Cells can only be produced through the process of cell division, specifically Mitosis.

Cell Types

• Somatic Cells: Non-reproductive cells in the body (e.g., skin, organs, muscles, bones).

• Gametes: Reproductive cells (sperm/egg).

  • Diploid (2n): Humans have 23 pairs (46 total chromosomes).

  • Haploid (n): Gametes contain 23 single chromosomes.

Chromosomes and DNA

• Chromosomes: Structures made of DNA wrapped around proteins (histones), condense during cell division from loose chromatin to visible form.

• Chromatids: The two identical halves of a chromosome.

• Centromere: Structure that holds sister chromatids together.

• Homologous Chromosomes: Chromosome pairs with the same genes but may carry different alleles (e.g., eye color).

Cell Cycle

• Cells spend most time in Interphase (90%), compared to Mitosis (10%).

• Interphase Stages:

  • G1 (Growth Phase 1): Rapid growth and replication of organelles.

  • S (Synthesis): DNA replication.

  • G2 (Growth Phase 2): Further growth and preparation for mitosis.

Mitosis Stages (PMAT)

1. Prophase:

   • Nucleus present; chromosomes condense.

   • Mitotic spindle begins to form.

2. Metaphase:

   • Chromosomes align in the cell's equatorial plane.

   • Nucleus disassembled.

3. Anaphase:

   • Sister chromatids are pulled apart to opposite poles of the cell.

4. Telophase:

   • Chromatids arrive at poles; nuclear membranes reform, creating two nuclei.

Cytokinesis

• The process that divides the cytoplasm, resulting in two daughter cells.

Chapter 16: Asexual and Sexual Reproduction

Asexual Reproduction

• Involves one parent and produces clones without gametes.

Sexual Reproduction

• Involves two parents combining genetic material through Meiosis.

• Meiosis introduces genetic variation.

Meiosis Process

• Two stages of cell division (Meiosis I and II).

• Reduction Division: Halves chromosome number from 46 to 23.

• Crossing Over: Genetic exchange during Prophase I increases diversity.

• Independent Assortment: Chromosome pairs line up randomly, creating unique gene combinations.

Meiosis Stages

Meiosis I

1. Prophase I:

   • Chromatids condense; homologous chromosomes pair (crossing over occurs).

2. Metaphase I:

   • Pairs of chromosomes align in the middle.

3. Anaphase I:

   • Chromosomes pulled apart; sister chromatids remain together.

4. Telophase I:

   • Two new cells formed.

Meiosis II

1. Prophase II:

   • Spindles form; no crossing over.

2. Metaphase II:

   • Chromosomes align in a single file in the middle.

3. Anaphase II:

   • Sister chromatids are separated.

4. Telophase II:

   • Nuclei reform; result in four haploid cells.

Chromosome Separation and Nondisjunction

• Errors in separation can lead to conditions from nondisjunction during anaphase I or II.

Chapter 17: Genetics

Key Terms

• Inherited Trait: Traits passed down genetically.

• Acquired Trait: Traits developed during life, not genetic.

• Heredity: Process of passing traits through genes.

• Genotype: Genetic makeup (pair of alleles).

• Phenotype: Physical appearance of a trait.

• Allele: Variants of a gene.

• Homozygous: Two identical alleles (e.g., BB or bb).

• Heterozygous: Two different alleles (e.g., Bb).

• Dominant Allele: Expressed in phenotype (capital letters).

• Recessive Allele: Only expressed when both alleles are recessive (lowercase).

Chromosome Types

• Autosomes: Chromosomes 1-22, not gender-related.

• Sex Chromosomes: Pair 23, determines biological sex (XX = female, XY = male).

Mendel's Discoveries

• F1 Generation: Offspring from two purebred parents; only dominant traits manifest.

• F2 Generation: Result of F1's self-pollination; recessive traits reappear in a 3:1 ratio.

Law of Segregation

• Each individual has two copies of each gene that segregate randomly into gametes during reproduction.

Monohybrid Cross & Allelic Interaction

• Focuses on one trait and its inheritance patterns.

Traits Beyond Simple Dominance

• Incomplete Dominance: Blending of traits (e.g., red and white flowers create pink).

• Codominance: Both traits are fully expressed (e.g., AB blood type).

Chapter 18: Molecular Genetics

DNA Structure

• DNA is composed of deoxyribose sugars, phosphates, and bases (A, T, C, G).

• RNA uses ribose and uracil instead of thymine.

DNA Replication Steps

• Helicase: Unzips DNA strands.

• DNA Polymerase: Builds the new strands of DNA.

• Primase: Creates RNA primers for initiation.

• Ligase: Seals DNA fragments together.

Protein Synthesis

1. Transcription: DNA to mRNA in the nucleus.

2. Translation: mRNA to proteins with the help of ribosomes and tRNA.

Mutations

• Changes in the DNA sequence can lead to cancer or other genetic disorders.

• Types of Mutations: Substitution, insertion, and deletion causes different effects on proteins.

• Nonsense Mutations: Lead to premature stop codons, potentially producing nonfunctional proteins.

Recombinant DNA Technology

• Involves cutting DNA with restriction enzymes, creating sticky ends, and sealing fragments to create new genetic combinations.

Biotechnology Applications

• Producing transgenic organisms, such as bacteria making insulin, and DNA microarrays to observe gene activity.