heredity

What is a gene?

A portion of the chromosome (DNA) responsible for a certain hereditary trait.

What is an allele?

A copy or version of a gene; e.g., the gene for the color of eyes has alleles like black, brown, and blue.

How is a dominant allele denoted?

A dominant allele is symbolized by an uppercase letter, e.g., Brown is represented as B.

How is a recessive allele denoted?

A recessive allele is symbolized by a lowercase letter, e.g., White is represented as w.

What is a genotype?

The set of alleles of an individual, e.g., BB, gg, Bg.

What is a homozygous organism?

An organism having two identical alleles of a gene, like AA or BB.

What is a heterozygous organism?

An organism having two different alleles of a gene, such as AB, AO, or BO.

What is a phenotype?

The set of observable characteristics of an individual that results from the expression of a genotype.

What are the alleles for blood types?

The alleles for blood types are A, B, and O.

Which alleles are dominant in blood types?

Alleles A and B are dominant, while allele O is recessive.

What is blood type AB's genotype?

The genotype for blood type AB is AB, which is heterozygous.

How is a recessive phenotype expressed?

A recessive phenotype is always expressed as a pure genotype such as OO.

What does it mean when alleles are codominant?

In codominance, both alleles are expressed, as seen in blood type AB.

What determines blood type A?

Blood type A can be either homozygous (AA) or heterozygous (AO) with allele A being dominant.