Unit 2 Essential Terminology 1. Alleles - different forms of a single gene. 2. Chromosome - coiled structure of DNA and protein that forms in the cell nucleus during cell division. 3. Cross-pollination - the process used to transfer pollen from one flower to the stigma to another. This allows for the selective breeding of two plants with different traits that may produce hybrid offspring with desirable traits. 4. DNA - deoxyribonucleic acid; hereditary material that controls all the activities of a cell, contains the information to make new cells, and provides instruction for making proteins. 5. Dominant trait - trait observed when at least one dominant allele for a characteristic is inherited. 6. Gene - segments of DNA that carries hereditary instructional information and are passed from parent to offspring; located on chromosomes. 7. Generation - body of living beings constituting a single step in the line of descent from an ancestor. 8. Genetics - branch of biology that deals with the heredity and variation of organisms. 9. Genetic engineering - directed alteration of genetic material by intervention in genetic processes. 10. Genotype - the inherited combination of alleles 11. Heredity - passing of traits from parent to offspring. 12. Heterozygous - having the two alleles at corresponding loci on homologous chromosomes different for one or more loci. 13. Homozygous - having the two genes at corresponding loci on homologous chromosomes identical for one or more loci. 14. Hybrid - offspring of two animals or plants of different races, breeds, varieties, species, or genera. 15. Meiosis - cell division that produces sex cells. 16. Pedigree - a diagram of family history used for tracing a trait through several generations. 17. Phenotype - an organism’s inherited appearance. 18. Punnet square - a n x n square used in genetics to calculate the frequencies of the different genotypes and phenotypes among the offspring of a cross. 19. Recessive trait - trait that is apparent only when two recessive alleles for the same characteristic are inherited. 20. Selective breeding - the breeding of organisms that have a specific desirable trait. 21. Trait - distinguishing quality that can be passed from one generation to another.