How do dominant and recessive alleles differ?

Dominant and recessive alleles are two types of genetic variants that can determine the traits an organism will express.

1. Definition: - A dominant allele is one that will express its trait even when paired with a different allele. It tends to mask the expression of the recessive allele. - A recessive allele is an allele that will only express its trait when two copies of it (one from each parent) are present. Its effect is masked by the presence of a dominant allele.

2. Expression Pattern: - In a dominant-recessive pair, if an organism has at least one dominant allele (represented typically by a capital letter, like "A"), the trait associated with the dominant allele will be observed. - The recessive trait (represented by a lowercase letter, like "a") will only be visible if the organism has two recessive alleles (aa), with no dominant allele to mask it.

3. Example: - Consider the trait for flower color in pea plants: purple flowers are dominant (P) and white flowers are recessive (p). A plant with the alleles PP or Pp will have purple flowers because the purple trait is dominant. Only a plant with pp (two recessive alleles) will have white flowers.

4. Genotypes and Phenotypes: - The genetic makeup of an organism, specifically the alleles they carry, is called its genotype (e.g., PP, Pp, or pp). - The physical expression of a trait, such as the color of the flowers, is called its phenotype (e.g., purple flowers or white flowers).

5. Homozygous and Heterozygous: - An organism that has two of the same alleles for a particular trait is said to be homozygous (PP or pp). - An organism with one dominant and one recessive allele for a trait is said to be heterozygous