Genetics Lecture Notes

Asexual Reproduction

• Definition: Reproduction without the fusion of gametes, producing offspring genetically identical to the parent.
• Mechanisms: Binary fission, budding, fragmentation, vegetative propagation.
• Genetic Material: Offspring inherit 100% of DNA from one parent.
• Advantages: Rapid population growth.
• Disadvantages: Less genetic variation, vulnerability to environmental changes.
• Examples: Bacteria, some plants, fungi, hydras, starfish.

Binary Fission

• Definition: Simple asexual reproduction seen in prokaryotes like bacteria.
• Process: DNA duplication followed by division into two identical cells.
• Outcome: Two clones of the parent cell.

Spores

• Definition: Reproductive cells produced by fungi, algae, plants.
• Characteristics: Haploid, resistant to harsh conditions, grow into new organisms without fertilization.
• Advantages: Quick, efficient reproduction without a mate.

Mitosis

• Purpose: Produces two genetically identical daughter cells from one parent cell.
• Uses: Growth, repair, asexual reproduction in multicellular organisms.

Phases of Mitosis

1. Prophase
   • Chromosomes condense; nuclear membrane breaks down; spindle fibers form.
2. Metaphase
   • Chromosomes line up at equator; spindle fibers attach to centromeres.
3. Anaphase
   • Sister chromatids pulled apart to opposite poles.
4. Telophase
   • Chromosomes reach poles, decondense; nuclear membranes reform.
5. Cytokinesis
   • Cytoplasm divides, forming two separate, identical cells.

Sexual Reproduction

• Definition: Involves fusion of two gametes from each parent, resulting in genetically unique offspring.
• Process: Meiosis produces haploid gametes; fertilization creates a diploid zygote.
• Genetic Variation: Introduced via independent assortment, crossing over, random fertilization.
• Organisms: Animals, most plants, fungi.

Key Terms

• Homologous Pairs: Matching chromosome pairs, one from each parent, containing the same genes.
• Diploid Cells (2n): Two sets of chromosomes; human somatic cells.
• Haploid Cells (n): One set of chromosomes; gametes.

Meiosis

• Purpose: Produces haploid gametes, introduces genetic variation.
• Stages: Two divisions — Meiosis I and Meiosis II.

Meiosis I

1. Prophase I
   • Chromosomes condense, pair up; crossing over occurs; nuclear membrane breaks down.
2. Metaphase I
   • Homologous pairs line up at equator.
3. Anaphase I
   • Homologous chromosomes pulled to opposite ends.
4. Telophase I & Cytokinesis
   • Two haploid cells form.

Meiosis II

1. Prophase II
   • New spindles form.
2. Metaphase II
   • Chromosomes line up at equator.
3. Anaphase II
   • Sister chromatids separate.
4. Telophase II & Cytokinesis
   • Four genetically unique haploid cells produced.

Inheritance

• Definition: Genetic information passed from parents to offspring.

Key Concepts

• Alleles: Different versions of a gene.
• Genotype: Genetic makeup (e.g., BB, Bb, bb).
• Phenotype: Physical expression of a genotype (e.g., brown eyes).
• Homozygous: Two identical alleles.
• Heterozygous: Two different alleles.

Punnett Square

• Purpose: Predicts possible genotypes and phenotypes of offspring.
• Process: Combines alleles from each parent to show genetic outcomes.

Year 10 Science Topics

Likely Topics for Study

1. Cell Division
   • Mitosis and Meiosis: phases, purposes, differences.
2. DNA and Genetics
   • DNA structure, genes, chromosomes.
3. Reproduction Types
   • Asexual vs Sexual: Definitions, examples, advantages/disadvantages.
4. Inheritance and Punnett Squares
   • Mendelian inheritance, genotypes, phenotypes.
5. Genetic Variation and Evolution
   • Causes and importance.
6. Vocabulary & Application
   • Key terms, applying knowledge to real-world examples.
7. Question Types
   • Multiple choice, short answer, diagrams, longer responses.