GCE O Level Biology: Definitions of Keywords from Cell division, Heredity and Molecular Genetics

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Terms in this set (28)
PhenotypeThe observable characteristic of an organismGenotypeGenetic composition of an organism, i.e. the combination of alleles it possessesHomozygousAn organism who has identical alleles for a particular trait. Eg. TT or TtHeterozygousAn organism who has unlike alleles for a particular trait. Eg. TtCodominanceCondition which arises when both alleles in a heterozygous organism are dominant and are fully expressed in the phenotypeMutationThe sudden or spontaneous change in gene structure or a chromosome, or chromosome number, and may be inheritableMutagenA physical, chemical or biological agent that causes mutation by altering the genetic materialContinuous variationRange of differences that can be observed in many characteristics in a population. It is brought about by combined effects of many gene and can be affected by environment.Discontinuous variationClearly defined differences in a characteristic that can be observed in a population. It is usually controlled by only one or a few genes and is not affected by the environment.Natural selectionProcess which results in the best adapted organisms in a population surviving to reproduceCodonTriplet of nucleotides within a molecule of messenger RNA that functions as a unit of genetic coding, usually by specifying a particular amino acid during the synthesis of proteins in a cellTranscriptionProcess where message stored in template DNA is copied to an mRNA moleculeTranslationProcess which uses the message stored in the mRNA to make a protein moleculeGenetic engineeringA technique used to transfer genes from one organism to anotherVectorAnother DNA molecule that is used to carry the genes of one organism into anotherPlasmidCircular DNA found in bacteriaRecombinant plasmidCircular DNA from bacteria that contains a foreign geneTransgenic organismAny organism which acquires a foreign gene, and a result of genetic engineering