homozygous
having two identical alleles for a trait
heterozygous
having two different alleles for a trait
pure
synonym of homozygous
hybrid
synonym of heterozygous
dominant
appears in an organism's phenotype if the allele is present
recessive
Shows up only when two alleles for the trait are inherited; often masked trait
alleles
different forms of a gene
trait
a characteristic that an organism can pass on to its offspring through its genes.
gene
A segment of DNA on a chromosome that codes for a specific trait
genotype
genetic makeup of an organism
phenotype
physical characteristics of an organism
incomplete dominance
when one allele doesn’t completely mask another resulting in a blending of both. (red + white = pink)
codominance
when one allele doesn’t mask another resulting in an individual that will show both alleles at the same time (red + white = red and white spots)
sex-linked traits
trait that is controlled by a gene found on a sex chromosome
Punnett square
a chart that shows all the possible combinations of alleles that can result from a genetic cross
pedigree
a diagram that shows the occurrence of a genetic trait in several generations of a family
Genetics
the branch of biology that studies heredity and variation in organisms
carrier
individual who has one copy of the allele for a recessive disorder and does not exhibit symptoms
double trait (two trait) cross
cross that shows how two different traits are passed on from parents to offspring
polygenic inheritance
when a trait is influenced by two or more genes
multiple alleles
having three or more alleles for a given gene
autosomal chromosome
one of the numbered chromosomes (1-22)
sex chromosome
chromosome involved in sex determination (X or Y)