Understanding Genetic Inheritance and Alleles

This comprehensive page explains the fundamental concepts of genetic inheritance and how genetics and alleles in genetic diagrams work. The text explores how genes control characteristics and how different versions of genes (alleles) influence inherited traits.

Definition: Genes exist in different versions called alleles, which are represented by letters in genetic diagrams.

Vocabulary:

• Homozygous: When an organism has two identical alleles for a particular trait
• Heterozygous: When an organism has two different alleles for a particular trait
• Dominant allele: Shown with a capital letter, overrules recessive alleles
• Recessive allele: Shown with a lowercase letter, only expressed when two copies are present

Example: A genetic diagram example showing hair color inheritance:

• When one parent has blonde hair (bb) and another has brown hair but carries the blonde allele (Bb)
• The resulting Punnett square shows:
  • 50% probability of brown hair offspring
  • 50% probability of blonde hair offspring

Highlight: Every chromosome in your body contains genes that control different characteristics. While some traits are controlled by a single gene, most characteristics result from several genes interacting together.

Quote: "Dominant alleles overrule recessive alleles, so if an organism has one dominant and one recessive gene (Bb), the dominant allele will determine which characteristic is present."