Biology A-Level AQA Keywords - Unit 4

Biology A-Level AQA Keywords - Unit 4 Gene - Section of DNA on a chromosome that controls a feature by coding for formation of one or more specific polypeptides or a functional RNA (including rRNA and tRNA). Chromosome - A thread like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next. Chromatin - The material that makes up chromosomes. It consists of DNA and the protein histone. Autosome - A chromosome which is not a sex chromosome Genetic code - The sequence of triplets of nucleotides (codons) in DNA which determines the sequence of amino acids in an organism's proteins. It is degenerate; non-overlapping; universal ; has start and stop codons Degenerate - A single amino acid may be coded for by more than one triplet code. Non-overlapping - Each base appears in only one triplet - each base is only read once. Universal - The genetic code is the same in all organisms - this is indirect evidence for evolution. Histones - Proteins, which together with DNA, make up the chromosomes of eukaryotic cells. Chromatid - Each of the two thread-like strands into which a chromosome divides that are joined together by a single centromere prior to cell division Locus - The specific linear position of a particular gene on a certain chromosome