One Shot: Heredity

Introduction

Heredity: The transfer of physical characteristics from parents to offspring
- E.g., hair color, eye color, height, etc.
Genes and Chromosomes: Physical characteristics are controlled by chromosomes and genes
- Present in DNA
- Transferred from parents to offspring
Gregor Mendel: Explained the principles of heredity using pea plants

Asexual Reproduction
- No gamete formation
- Little to no changes in DNA
- Mostly stable genetic makeup (e.g., bacteria)
Sexual Reproduction
- Contribution from both male and female genes
- DNA copy through meiotic division
- Occasional changes
Variations
- Minor changes during DNA copying
- May or may not be useful according to environmental factors
Mutation
- Variations occur when there is damage in DNA copying
Importance of Variations
- Helps in adaptation to environmental changes
- Play a role in evolution and the emergence of new species

Father of Genetics: Gregor Mendel
Pea Plant Selection
- Possible self-pollination and cross-pollination
- Offspring generate quickly
- Many different characteristics
Monohybrid Cross
- Study of a single characteristic
- Cross of T (Tall) and t (Dwarf)
- All offspring tall in F1 generation
- 3 tall and 1 dwarf in F2 generation
- Law of Dominance: One characteristic is dominant, the other is recessive
Dihybrid Cross
- Study of two characteristics
- Cross of R (Round), r (Wrinkled), Y (Yellow), y (Green)
- 9:3:3:1 phenotypic ratio in F2 generation
- Law of Independent Assortment: Characteristics assort independently during gamete formation

Males: X and Y chromosomes
Females: Only X chromosomes
Sperm
- Fertilization of X ovum by X sperm -> XX (Female child)
- Fertilization of X ovum by Y sperm -> XY (Male child)
Which Gamete Determines Sex
- The male sperm is primarily responsible