Download Biology Monday, January 7

Genetics Vocabulary
Genetics: The study of inheritance
Gene – a piece of chromosome (DNA)
that codes for a trait
 Allele – a form of a gene (written as a
letter that stands for the trait)
Ex: R- handedness (right or left handed)
Hint: Always choose a letter that looks
different when written in capital and
lower case. (Don’t use S or C.)

Complete Dominance
Dominant – a trait that will always be
expressed (shown) if it is present, written
as a capital letter
Ex: R- Right-handedness
 Recessive – a trait that will only be
expressed if the dominant allele is not
present, written as a lower case letter
Ex: r – Left-handedness

Homozygous – same alleles
(also called purebred)
Ex: RR or rr
 Heterozygous – two different alleles
(also called hybrid)
Ex: Rr
 Genotype – genetic makeup
Ex: Rr
 Phenotype – physical appearance
Ex: Right-handed

Punnett Squares

Punnett Squares are used to determine
the likelihood of two parents having
children with various genotypes and
phenotypes.