Template:Introduction to genetics glossary
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A segment of the DNA in a chromosome. Genes are like sentences built up of the "letters" of the nucleotide alphabet, and between them the genes direct the physical development and behavior of the organism. A set of genes acting together are like a recipe or instruction book, providing the information that a living organism needs so it can build or do something - like making an eye or a leg, or repairing a wound. The different forms of a given gene that an organism may possess. For example, in humans, one allele of the eye-color gene produces green eyes and another allele of the eye-color gene produces brown eyes. A long molecule that has the form of a "double helix", which looks like a twisted ladder. It is made of four types of simple units and the sequence of these units carries information, just as the sequence of letters carries information on a page.
They form the rungs of the DNA ladder and are the repeating units in DNA. In the rotating image above they are the flat blue and gray parts at the center of the molecule. There are four types of nucleotides (A, T, G and C) and it is the sequence of these nucleotides that carries information. A package for carrying DNA in the cells. They contain a single long piece of DNA that is wound up and bunched together into a compact structure. Different species of plants and animals have different numbers and sizes of chromosomes.
The complete set of genes in a particular organism. When people change an organism by adding new genes, or deleting genes from its genome. An event that changes the sequence of the DNA in a gene. |