Genetic Variation 2 Monohybrid inheritance to linked genes.

Dominant allele

An allele whose trait always shows up in the organism when the allele is present.

Recessive allele

An allele that is hidden whenever the dominant allele is present. Both alleles need to be in recessive form for it to be expressed.

Genotype

Alleles that make up the genotype of an organism

Phenotype

Characteristics expressed in an organism

Homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

Gene

A segment of DNA on a chromosome that codes for a specific trait.

Pure breeding

Homozygous (dominant or recessive) for the phenotypes being questioned about.

Test cross

The crossing of an individual of unknown genotype (dominant phenotype) with a homozygous recessive individual to determine the unknown genotype.

Dihybrid inheritance

The inheritance of two characteristics which are controlled by different genes

Pedigree chart

A chart which shows several generations of related families and how traits are passed down through the offspring.

Co-dominance

A condition in which both alleles for a gene are full expressed.

Incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Linked genes

Genes located close enough together on a chromosome that they tend to be inherited together. They do not separate(segregate) independently at meiosis unless chiasma have formed between them.