Biology A2

Gene: A length of DNA that codes for the production of a particular plypeptide or protein.  

Chromosome: Highly condensed DNA molecule that appears in a cell just before cell division.  The name means couloured body

Chromatids: Either of the two strands that make up a chromosome

Centromere: region where the two chrimatids in a chromosome are joined together.

Diploid: cell or organism that possesses two set of chromosomes.  

homologous: having the same genes in the same positions; in a diploid cell there are homologous pair of each type of chromosomes.  

Locus: position of an allel on a chromosome

Allele: alternative from of a gene.  

Genotype: The particular alleles an organism process.  

Phenotype: The observable features an organism possesses.  Simply put: pheotype = gentoype + enviroment.  

Gene pool: The sum total of the alleles circulating in an interbreeding population.  

Directional selection: Type of natural selectionthat favours one extreme of phenotype, for example talles, quickest, heaviest.  

Reproductively isolated: Unable to breed with other populations, because of differences in for example behaviour or physiology