117 Key Terms (104/84) -- Biology Part I

117 Key Terms - allele - gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes - autosomes - any of the non-sex chromosomes - blending theory of inheritance - hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance - carriers - heterozygous individual or organism that carries a recessive allele that is not contributing to the phenotype. Relevant in medicine for recessive alleles that cause genetic disease(s) in homozygous offspring - chromosomal basic of heredity - also known as Chromosomal Theory of Inheritance. A theory proposing that chromosomes are the genes’ vehicles and that their behavior during meiosis is the physical basis of the inheritance patterns that Mendel observed - codominance - in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic - continuous variation - inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them - dihybrid - result of a cross between two true-breeding parents that express different traits for two characteristics - discontinuous variation - inheritance pattern in which traits are distinct and are transmitted independently of one another - dominant - trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait - dominant lethal - inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age - epistasis - antagonistic interaction between genes such that one gene masks or interferes with the expression of another - F1 - first filial generation in a cross; the offspring of the parental generation - F2 - second filial generation produced when F1 individuals are self-crossed or fertilized with each other - genetics - the study of heredity - genotype - underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism - hemizygous - 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 chromosome - homozygous - having two identical alleles for a given gene on the homologous chromosome - hybridization - 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