Term
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Definition
| offspring of individuals that differ with regard to certain traits or certain aspects of genetic makeup; heterozygotes. |
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Term
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Definition
| genes (alleles) occur in pairs (because chromosomes occur in pairs). during gamete production, the members of each gene pair separate, so that each gamete contains one member of each pair. during fertilization, the full number of chromosomes is restored, and members of gene or allele pairs are reunited. |
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| describing a trait that is not expressed in heterozygotes; also refers to the allele that governs the trait. for a recessive allele to be expressed, there must be two copies of the allele (i.e., the individual must be homozygous). |
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Definition
| describing a trait governed by an allele that can be expressed in the presence of another, different allele (i.e. in heterozygotes). dominant alleles prevent the expression of recessive alleles in heterozygotes. (this is the definition of complete dominance.) |
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Term
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Definition
| (pl., loci) (lo'-kus, lo-sigh') the position on a chromosome where a given gene occurs. the term is sometimes used interchangeably with gene, but this usage is technically incorrect. |
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Term
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Definition
| alternate forms of a gene. alleles occur at the same locus on homologous chromosomes and thus govern the same trait. however, because they are slightly different, their action may result in different expressions of the trait. the term is sometimes used synonymously with gene. |
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Definition
| having the same allele at the same locus on both members of a chromosome pair. |
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Definition
| having different alleles at the same locus on members of a chromosome pair. |
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Definition
| the genetic makeup of an individual. genotype can refer to an organism's entire genetic makeup or the alleles at a particular locus. |
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Definition
| the observable or detectable physical characteristics of an organism; the detectable expressions of genotypes. |
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Term
| principle of independent assortment |
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Definition
| the distribution of one pair of alleles into gametes doesn't influence the distribution of another pair. the genes controlling different traits are inherited independently of one another. |
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Term
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Definition
| the chance distribution of chromosomes to daughter cells during meiosis. there is nothing to dictate which member of a chromosome pair moves to which end of a dividing cell. along with recombination, a source of variation resulting from meiosis. |
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Term
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Definition
| characteristics that are influenced by alleles at only one genetic locus. examples include many blood types, such as ABO. many genetic disorders, including sickle-cell anemia and Tay-Sachs disease, are also Mendelian traits. |
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Term
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Definition
| large molecules found on the surface of cells. several different loci govern various antigens on red and white blood cells. |
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Definition
| the expression of two alleles in heterozygotes. in this situation, neither allele is dominant or recessive; thus, both influence the phenotype. |
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Term
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Definition
| referring to traits that are influenced by genes at two or more loci. examples of such traits are stature, skin color, and eye color. many polygenic traits are also influenced by environmental factors. |
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Definition
| inherited differences among individuals; the basis of all evolutionary change. |
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Term
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Definition
| (modern genetic definition) a change in the frequency of alleles from one generation to the next. |
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Term
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Definition
| in a population, the percentage of all the alleles at a locus accounted for by one specific allele. |
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Term
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Definition
| within a species, a community of individuals where mates are usually found. |
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Definition
| small changes occuring within species, such as a change in allele frequencies. |
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Definition
| changes produced only after many generations, such as the appearance of a new species. |
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Definition
| exchange of genes between populations |
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Definition
| evolutionary changes- that is, changes in allele frequencies- produced by random factors. genetic drift is a result of small population size. |
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Definition
| a type of genetic drift in which allele frequencies are altered in small populations that are taken from, or are remnants of, larger populations. |
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Term
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Definition
| the total complement of genes shared by the reproductive members of a population. |
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