Alleles
Alternate forms or varieties of a gene. The alleles for a trait occupy the same locus or position on homologous chromosomes and thus govern
... [Show More] the same trait. However, because they are different, their action may result in different expressions of that trait.
Carrier
An individual who is heterozygous for a trait that only shows up in the phenotype of those who are homozygous recessive. Carriers often do not show any signs of the trait but can pass it on to their offspring. This is the case with hemophilia.
Chromosomes
Thread-like, gene-carrying bodies in the nucleus of a cell. Chromosomes are composed primarily of DNA and protein. They are visible only under magnification during certain stages of cell division. Humans have 46 chromosomes in each somatic cell and 23 in each sex cell.
Codominance
The situation in which two different alleles for a trait are expressed unblended in the phenotype of heterozygous individuals. Neither allele is dominant or recessive, so that both appear in the phenotype or influence it. Type AB blood is an example. Such traits are said to be codominant.
Cross-pollination
The mating of two genetically different plants of the same species. Usually, the term is used in reference to the crossing of two pure breeding (homozygous) plants.
• Dominant allele
• An allele that masks the presence of a recessive allele in the phenotype. Dominant alleles for a trait are usually expressed if an individual is homozygous dominant or heterozygous.
• DNA (Deoxyribonucleic acid)
• A large organic molecule that stores the genetic code for the synthesis of proteins. DNA is composed of sugars, phosphates and bases arranged in a double helix shaped molecular structure. Segments of DNA in chromosomes correspond to specific genes.
• Evolution
• Genetic change in a population of organisms that occurs over time. The term is also frequently used to refer to the appearance of a new species.
• F1 generation
• The first offspring (or filial) generation. The next and subsequent generations are referred to as f2, f3, etc.
• Gene pool
• All of the genes in all of the individuals in a breeding population. More precisely, it is the collective genotype of a population.
• Genes
• Units of inheritance usually occurring at specific locations, or loci, on a chromosome. Physically, a gene is a sequence of DNA bases that specify the order of amino acids in an entire protein or, in some cases, a portion of a protein. A gene may be made up of hundreds of thousands of DNA bases. Genes are responsible for the hereditary traits in plants and animals.
• Genetic drift
• Evolution, or change in gene pool frequencies, resulting from random chance. Genetic drift occurs most rapidly in small populations. In large populations, random deviations in allele frequencies in one direction are more likely to be cancelled out by random changes in the opposite direction.
• Genetics
• The study of gene structure and action and the patterns of inheritance of traits from parent to offspring. Genetic mechanisms are the underlying foundation for evolutionary change. Genetics is the branch of science that deals with the inheritance of biological characteristics.
• Genome
• The full genetic complement of an individual (or of a species). In humans, it is estimated that each individual possesses approximately 2.9 billion base units in his or her DNA. See Human Genome Project. [Show Less]