AP BIO: Heredity
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23 terms
Terms | Definitions |
|---|---|
 Gene | genetic material on a chromosome that contains the instructions for creating a particular trait |
| Allele | one of several varieties of a gene |
| Locus | location on a chromosome where a gene is located |
| Homologous chromosomes | pair of chromosomes that contains the same genetic information |
| Dominant | trait expressed |
| Recessive | trait not expressed |
| Phenotype | actual expression of a gene |
| Genotype | actual alleles |
| Law of segregation | separation of alleles to individual gametes |
| Law of independent assortment | independent assortment of alleles |
| Incomplete dominance | expression of two different alleles in the heterozygous condition produces a blending of the individual expressions of the two alleles |
| Codominance | both inherited alleles are completely expressed (blood type) |
| Epistasis | one gene affects the phenotypic expression of a second gene (skin pigmentation) |
| Pleiotropy | single gene has more than one phenotypic expression |
| Polygenic inheritance | interaction of many genes to shape a single phenotype |
| Linked genes | genes that reside on the same chromosome and cannot segregate independently because they are physically connected |
| Sex-linked genes | genes that reside on the X chromosome |
| Barr body | inactive X chromosomes (most of the genes are not expressed or do not interact) |
| Nondisjunction | failure of one or more chromosome pairs or chromatids of a single chromosome to properly separate during meiosis or mitosis |
| Point mutations | single nucleotide in the DNA sequence is incorrect; substitution, insertion, or deletion |
| Aneuploidy | genome with extra or missing chromosomes |
| Down syndrome | egg or sperm with an extra number 21 chromosome fuses with a normal gamete; three copies of chromosome 21 |
| Turner syndrome | nondisjunction of the sex chromosomes |
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