Genetics

Genetics

The study of how traits are passed from parents to offspring.

Allele

A different form of a gene for a trait (ex: brown eyes or blue eyes).

Dominant

An allele that is always expressed when present.

Recessive

An allele that is only expressed when two copies are present.

Incomplete Dominance

When two alleles blend together to produce a mixed trait (ex: red + white flowers → pink).

Co-Dominance

When both alleles are fully expressed at the same time (ex: AB blood type).

Heterozygous

Having two different alleles for a trait (ex: Aa).

Homologous (Chromosomes)

A pair of chromosomes that carry the same genes for the same traits.

Punnett Square

A chart used to predict the possible genetic outcomes of a cross.

Genotype

The genetic makeup of an organism (the allele combination, ex: AA, Aa).

Phenotype

The physical appearance or trait that is expressed (ex: brown eyes).

Sex-Linked

A trait controlled by genes located on the X or Y chromosome.

Pedigree

A chart that shows how a trait is inherited through a family.

Segregation (Law of Segregation)

Alleles separate during gamete formation so each gamete gets only one allele.

Independent Assortment

Genes for different traits are inherited independently of each other.

Genetic Disorder

A disease caused by a problem in a gene or chromosome.

Carrier

A person who has a recessive allele for a disorder but does not show the disease.

Hemophilia

A sex-linked genetic disorder where blood does not clot properly.

Fraternal Twins

Twins that come from two different eggs and sperm; genetically like regular siblings.

Identical Twins

Twins formed when one fertilized egg splits; they have identical DNA.