Term | Definition |
Gene | sequence of DNA that codes for an organism's traits. |
Chromosome | Supercoiled DNA packaged for mitosis or meiosis. |
Homologous | A pair of chromosomes in which one chromosome is from the mother and one chromosome is from the father. |
Sister chromatid | refers to the identical copies formed by the replication of a chromosome. |
Incomplete dominance | one allele is not completely dominant over another, resulting in a phenotype that is a blending of traits. |
Codominance | both alleles of a gene are visible in the phenotype of the organism. |
Multiple alleles | three or more alleles for the same gene. |
Sex-linked | genes located on the sex chromosomes X or Y(pair #23). |
Polygenic | the determination of a particular characteristic, e.g. height or skin color, by many genes. |
Autosomes | all chromosomes excluding the sex chromosomes (pairs #1-22). |
Meiosis | the reduction division process when haploid (n) gametes are formed. |
Gamete | a reproductive (sex) cell; egg and sperm. |
Pedigree | a chart showing a family lineage; used to track a genetic disorder within a family. |
Karyotype | a picture of chromosomes arranged in their homologous pairs. |
Mutation | a permanent, heritable change in the nucleotide sequence in a gene or a chromosome. |
Nondisjunction | sister chromatids fail to separate during meiosis causing abnormal numbers of chromosomes in gametes. |
Recombination | genes on homologous chromosomes are recombined to produce organisms with new gene combinations |
Crossing Over | The chromatids break into segments (of matching regions), which are then exchanged with one another. |
Genotype | genetic makeup of an organism represented by letters (Hh) in a Punnett square. |
Phenotype | physical characteristics of an organism. Ex: blue eyes |
Haploid (n) | single copy of chromosome set |
Diploid (2n) | two copies of the chromosome set |
Homozygous | identical pairs of alleles for the same trait. Ex: HH or hh |
Heterozygous | two different alleles for the same trait. Ex: Hh |