Zygote
the single cell formed from fertilization
Gamete
a specialized haploid sex cell
Haploid
(1n) – a specialized cell that contains half the chromosome number
Diploid
(2n) – the cells which contain two homologous copies of each chromosome
Crossing over
he exchange of corresponding regions on chromosomes
during meiosis
Codominance
two dominant alleles are expressed at the
same time without blending of traits
– Heterozygous individuals display both phenotypes
– Both alleles represented by capital letters
Monohybrid cross
a genetic cross involving individuals both heterozygous for one trait
Dihybrid cross
a breeding experiment between two organisms which are identical hybrids for two traits.
Dominant allele
A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent.
Recessive allele
For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent.
Phenotype
the physical and physiological traits of an organism
– Descriptive
Genotype
the genetic makeup of an organism
– Written as two letters
Heterozygous
the state of having two different alleles for a given genetic character
Homozygous dominant
the state of having two of the same alleles for a given genetic character
ex: RR
Homozygous recessive
the state of having two of the same alleles for a given genetic character
ex: rr
Incomplete dominance
a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype
Multiple alleles
the three or more different forms of a gene for the same trait, each producing a single phenotype
Polygenic inheritance
quantitative inheritance, where multiple independent genes have an additive or similar effect on a single quantitative trai
P generation
the first set of parents which are used for crossing
F1 generation
the first filial generation seeds/plants or animal offspring resulting from a cross-mating of distinctly different parental types
F2 generation
a group of people born as a result of inbreeding and interbreeding among members of the same family
sister chromatids
one of the two identical halves of a chromosome that has been replicated in preparation for cell division.
tetrad
the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.