Understanding Variation and Inheritance

This comprehensive page explores fundamental concepts in genetics and inheritance, focusing on how characteristics are passed between generations and expressed in organisms.

Definition: Variation refers to the differences between individuals of the same species, resulting from random fertilization processes.

Example: Phenotype ratios in genetic crosses:

• Heterozygous × Heterozygous: 3 dominant to 1 recessive
• Heterozygous × Homozygous recessive: 1 dominant to 1 recessive

Vocabulary: Key genetic terms and their meanings:

• Allele: Different forms of a gene
• Dominant: Stronger allele (capital letter)
• Recessive: Weaker allele (small letter)
• Gamete: Sex cell
• Heterozygous: Individual with two different alleles
• Homozygous: Individual with two identical alleles
• Phenotype: Physical characteristics
• Genotype: Set of genes possessed

Highlight: Two main types of variation:

1. Continuous Variation: Shows a range of values (height, weight, pulse rate)
2. Discrete Variation: Falls into distinct groups (eye color, tongue rolling, blood group)

Definition: Inheritance patterns:

• Single-gene inheritance: Characteristics controlled by one gene
• Polygenic inheritance: Characteristics controlled by multiple genes