Heredity and Genetics Overview

Heredity and Genetics

• Heredity is the passing of traits from parents to offspring.
• Genetics is the study of heredity and how traits are inherited.

Genotype and Phenotype

• Genotype: The genetic makeup of an individual, represented by the alleles they possess.
• Phenotype: The physical expression of the genotype, what we can observe.

Alleles and Traits

• Gene: A segment of DNA that codes for a specific trait.
• Allele: A version of a gene, there are usually two or more alleles for each gene.
• Trait: A specific characteristic or feature of an organism.

Homozygous and Heterozygous

• Homozygous: An individual with two identical alleles for a particular gene.
• Heterozygous: An individual with two different alleles for a particular gene.

Dominant and Recessive Alleles

• Dominant allele: An allele that expresses its trait even when paired with a recessive allele.
• Recessive allele: An allele that is only expressed when paired with another recessive allele.

Inheritance Patterns

• Carrier: An individual who carries a recessive allele for a trait but does not express it.
• True-breeding: Individuals that consistently produce offspring with the same traits as themselves.
• Hybrid: An individual that results from the cross of two different true-breeding individuals, leading to offspring with different versions of the traits.

Laws of Inheritance

• Law of Dominance: When two different alleles for a trait are present, the dominant allele masks the expression of the recessive allele.
• Law of Segregation: Each parent contributes only one allele to their offspring for each trait.
• Law of Independent Assortment: Different traits are inherited independently of each other.

Monohybrid Cross

• A cross between two individuals that differ in only one trait.
• Example: Brown eyes (B) are dominant to blue eyes (b). A cross between a homozygous brown-eyed parent (BB) and a homozygous blue-eyed parent (bb) will result in all offspring having brown eyes (Bb).

Dihybrid Cross

• A cross between two individuals that differ in two traits.
• Example: Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A dihybrid cross between two individuals that are heterozygous for both traits (RrYy) will result in 16 possible combinations of offspring.

Generations

• P generation: The original parental generation in a cross experiment.
• F1 generation: The first generation of offspring produced from the P generation.
• F2 generation: The second generation of offspring produced from a cross between two F1 individuals.