Chapter 5 pgs 138-147
Allele: One of several alternative forms of the DNAsequence of the same locus.
Meiosis:Aform of cell division that occurs only in eukaryotes, in which the number of chromosomes is
cut in half. Meiosis gives rise to gametes or spores and is essential for sexual reproduction.
Genetic Recombination: The exchange of genetic material between paired chromosomes during
meiosis. Recombination can form new combinations of alleles and is an important source of
Genotype: The genetic makeup of an individual.Although a genotype includes all the alleles of all the
genes in that individual, the term is often used to refer to the specific alleles carried by an
individual for any particular gene.
Phenotype:An observable, measurable characteristic of an organism.Aphenotype may be a
morphological structure (e.g., antlers, muscles), a developmental process (e.g., learning), a
physiological process or performance trait (e.g., running speed), or a behavior (e.g., mating
display). Phenotypes can even be the molecules produced by genes (e.g., hemoglobin).
Genetic Polymorphism: The simultaneous occurrence of two or more discrete phenotypes within a
population. In the simplest case, each phenotype results from a different allele or combination
of alleles of a single gene. In more complex cases, the phenotypes result from complex
interactions between many different genes and the environment.
Polyphenic Trait:Atrait for which multiple, discrete phenotypes can arise from a single genotype
depending on environmental circumstances.
Quantitative Traits: Measurable phenotypes that vary among individuals over a given range to produce
a continuous distribution of phenotypes. Quantitative traits are sometimes called complex traits;
they're also sometimes called polygenic traits because their variation can be attributed to
polygenic effectss (i.e., the cumulative action of many genes).
Morphogen:Asignaling molecule that flows between nearby cells and acts directly to alter expression
of target genes.
Phenotypic Plasticity: Changes in the phenotype produced by a single genotype in different
– Organisms pass down mutations, along with unmutated DNA