Heredity Flashcards
Gene
a unit of inheritance that usually is directly responsible for one trait or character. Each individual has two genes for each trait, one comes from dad and the other from mom.
Allele
allele - alternate forms of a gene. Usually there are two alleles for every gene, sometimes as many a three or four present in population
Homozygous
when the two alleles are the same
Heterozygous
when the two alleles are different
Dominant
a trait (allele) that is expressed regardless of the second allele
Recessive
a trait that is only expressed when the second allele is the same (e.g. short plants are homozygous for the recessive allele)
Punnett Square
probability diagram illustrating the possible offspring of a mating male genes on top of columns and female traits on side of rows
Autosome
not a sex chromosome (22 pairs)
Sex Chromosome
not an autosome (1 pair)
two x’s for girls
one x and one y for boys
Hybrid
an individual who has one dominant and one recessive gene for a trait (heterozygous)
Purebred
an individual who has either two dominant or two recessive genes. (homozygous) (same as true breeding)
Phenotype
the physical expression of the genes for the trait by an individual
Genotype
the gene makeup of an organism. Phenotype is the trait of an individual expresses while genotype is the two genes that cause that trait
Incomplete Dominance
one allele (gene) is not completely dominant over another resulting in a blending of traits and where the phenotype of a hybrid displays a blending of the two alleles
Co-dominance
both dominant alleles (genes) in an individual are expressed as in blood types
