1.9A Obj 11A Genetics (Basic Vocab)

Allele

Different forms of a gene

Allele examples

Purple v white flowers; P v p

Gene

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

Gene examples

Flower color, pea pod color

dominant allele

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

dominant allele example

In Ww it is the capital W

recessive allele

An allele that is masked when a dominant allele is present

recessive allele example

In Ww it is the lower case w

Phenotype

An individual’s observable traits.

Genotype

An organism's genetic makeup, or allele combinations.

Genotype examples

TT, Tt, tt

Genotypic Ratio Example

1 PP : 2 Pp : 1 pp

Phenotypic Ratio Example

3 purple: 1 white

Homozygous

Having two identical alleles for a particular gene

homozygous dominant genotype

RR

homozygous recessive genotype

aa

Heterozygous

having two different alleles for a particular gene

heterozygous genotype

Bb

P generation

Parental generation, the first two individuals that mate in a genetic cross

Purebred

type of organism whose ancestors are genetically uniform

F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation

Mendel's Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

Mendel's Law of Independent Assortment

genes found on different chromosomes are sorted into sex cells independently of one another

monohybrid cross

A cross between two individuals, concentrating on only one definable trait

dihybrid cross

A cross between two individuals, concentrating on two definable traits