Term | Definition |
1. heredity | the passing of genetic traits from parent to offspring |
2. Genetics | the science of heredity and of the mechanisms by which traits are passed from parents to offspring |
3. monohybrid | a cross between individuals that involves one pair of contrasting traits |
4. P generation | parental generation, the first two individuals that mate in a genetic cross |
5. F1 generation | the first generation of offspring obtained from an experimental cross of two organisms |
6. F2 generation | the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation |
7. allele | one of the alternative forms of a gene that governs a characteristic, such as hair color |
8. dominant | the expressed form of a trait |
9. recessive | the trait that is not expressed when the dominant form of the trait was present |
10. homozygous | describes an individual that has identical alleles for a trait on both homologous chromosomes |
11. heterozygous | describes an individual that has two different alleles for a trait |
12. genotype | the entire genetic makeup of an organism; also the combination of genes for one or more specific traits |
13. phenotype | an organism's appearance or other detectable characteristic that results from the organism's genotype and the environment |
14. law of segregation | Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete |
15. law of independent assortment | the law that states that genes separate independently of one another in meiosis |
16. Punnett square | a graphic used to predict the results of a genetic cross |
17. test cross | the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotypes |
18. probability | the likelihood that a possible future event will occur in any given instance of the event; the mathematical ratio of the number of times one outcome of any event is likely to occur to the number of possible outcomes of the event |
19. pedigree | a diagram that shows the occurrence of a genetic trait in several generations of a family |
20. sex-linked traits | a trait that is determined by a gene found on one of the sex chromosomes, such as the X chromosomes or the Y chromosomes in humans |
21. polygenic trait | a characteristic of an organism that is determined by many genes |
22. incomplete dominance | a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully |
23. multiple alleles | more than two alleles (versions of a gene) for a genetic trait |
24. codominance | a condition in which both alleles for a gene are fully expressed |
25. vaccine | substance prepared from killed or weakened pathogens and introduced into a body to produce immunity |