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16 November, 2015 - 15:23
allele one of two or more variants of a gene that determines a particular trait for a characteristic
codominance in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic
continuous variation a variation in a characteristic in which individuals show a range of traits with small differences between them
dihybrid the result of a cross between two true-breeding parents that express different traits for two characteristics
discontinuous variation a variation in a characteristic in which individuals show two, or a few, traits with large differences between them
dominant describes a trait that masks the expression of another trait when both versions of the gene are present in an individual
epistasis an interaction between genes such that one gene masks or interferes with the expression of another
F1 the first filial generation in a cross; the offspring of the parental generation
F2 the second filial generation produced when F1 individuals are self-crossed or fertilized with each other
genotype the underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism
hemizygous the presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant
heterozygous having two different alleles for a given gene on the homologous chromosomes
homozygous having two identical alleles for a given gene on the homologous chromosomes
hybridization the process of mating two individuals that differ, with the goal of achieving a certain characteristic in their offspring
incomplete dominance in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype
law of dominance in a heterozygote, one trait will conceal the presence of another trait for the same characteristic
law of independent assortment genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur
law of segregation paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors
linkage a phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together
model system a species or biological system used to study a specific biological phenomenon to gain understanding that will be applied to other species
monohybrid the result of a cross between two true-breeding parents that express different traits for only one characteristic
P the parental generation in a cross
Punnett square a visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid
phenotype the observable traits expressed by an organism
recessive describes a trait whose expression is masked by another trait when the alleles for both traits are present in an individual
reciprocal cross a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross
recombination the process during meiosis in which homologous chromosomes exchange linear segments of genetic material, thereby dramatically increasing genetic variation in the offspring and separating linked genes
test cross a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait
trait a variation in an inherited characteristic
wild type the most commonly occurring genotype or phenotype for a given characteristic found in a population
X-linked a gene present on the X chromosome, but not the Y chromosome