Definition: Dominant alleles are represented by capital letters and mask the effects of recessive alleles, while recessive alleles are represented by lowercase letters and are usually hidden.

Example: B represents the dominant allele for brown eyes, while b represents the recessive allele for blue eyes.

Highlight: The combination of alleles received from parents determines an individual's genotype and phenotype.

Definition: Genotype is the genetic makeup of an organism determined by the alleles received, while phenotype is the physical appearance of a trait determined by the genotype.

Example: A person with the genotype BB or Bb will have brown eyes (phenotype), while someone with bb will have blue eyes.

Highlight: The relationship between genotype and phenotype is crucial for understanding how genetic information is expressed in an organism's characteristics.

Definition: Simple dominance occurs when a dominant allele completely hides the recessive allele, requiring only one dominant allele to express the dominant trait.

Example: Brown eyes (B) are dominant over blue eyes (b), so individuals with BB or Bb genotypes will have brown eyes.

Highlight: Many common human traits, such as cleft chin, widow's peak, and freckles, follow the pattern of simple dominance.

Definition: A Punnett square is a diagram that predicts the possible genotypes and phenotypes of offspring from a genetic cross.

Example: A Punnett square for a cross between two heterozygous parents (Bb x Bb) shows the probability of offspring genotypes and phenotypes.

Highlight: Punnett squares are essential tools in genetics for predicting inheritance patterns and probabilities.