| A | B |
|---|
| character | heritable feature that varies among individuals |
| trait | each variant for a character |
| true-breeding | plants that produce offspring of the same variety when they self-pollinate |
| hybridization | crossing of two true-breeding varieties |
| P generation | true-breeding parents |
| F1 generation | hybrid offspring |
| F2 generation | offspring resulting from interbreeding of F1 generation |
| alleles | alternative versions of a gene |
| dominant allele | allele that is fully expressed |
| recessive allele | the allele that is completely mased by the phenotype |
| law of segregation | allele pairs seperate during gamete formation, and then randomly re-form as pairs during the fusion of gametes at fertilization |
| Punnett Square | diagram used in the study of inheritance to show the results of random fertilization |
| homozygous | identical alleles |
| heterozygous | two different alleles |
| phenotype | organism's traits |
| genotype | organism's genetic makeup |
| monohybrids | organism that is heterozygous with respect to a single gene of interest |
| dihybrids | organism that is heterozygous with respect to two genes of interest |
| testcross | breeding of a recessive homozygote with an organism of dominant phenotype but unknown genotype |
| law of independent assortment | each allele pair segregates independently during gamete formation |
| incomplete dominance | type of inheritance in which F1 hybrids have an appearence that is intermediate between the phenotypes of the parental varieties |
| complete dominance | type of inheritance in which phenotypes of heterozygote and dominat monozygote are indistinguishable |
| codominance | phenotypic situation in which the two alleles affect the phenotype in seperate, dinstinguishable ways |
| epistasis | gene at one locus alters the phenotypic expression of a gene at a second locus |
| quantitative characters | heritable feature in popualtion that varies continuously as a result of environmental influences and the additive effect of two or more genes |
| polygenic inheritance | an additive effect of two or more gene loci on a single phenotypic character |
| norm of reaction | range of phenotypic possibilities for a single genotype, as influenced by the environment |
| multifactorial | many factors, gentic & environmental, collectively influence phenotype |
| pedigree | family tree describing the occurence of heritable characters in parents & offspring across as many generations as possible |
| cystic fibrosis | most common lethal genetic disease in US, occurs in people with two copies of a certain recessive allele, characterized by an excessive secretion of mucus & consequent vulnerability to infection, fatal if untreated |
| Tay-Sachs disease | human genetic disease caused by a dysfunctional enzyme that fails to break down brain lipids of a certain class, causes seizures, blindness, & degeneration of motor & mental performance usually manifests a few months after birth |
| sickle-cell disease | human genetic disorder of red blood cells caused by the subsitution of a single amino acid in the hemoglobin protein, most prevalent in African Americans |
| Huntington's disease | human genetic disease caused by a dominant allele, characterized by uncontrollable body movements & degeneration of the nervous system, usually fatal 10-20 years after onset of symptoms |
| amniocentesis | technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid |
| chorionic villus sampling (CVS) | technique for diagnosing genetic & congenital defects in a fetus by removing & analysing small part of the fetal portion of placenta |
