A gene is a sequence of Nucleotide bases that code for a specific protein or polypeptide. Genes are mainly located on the Chromosomes however some can be found in mitochondria. Each gene occupies a specific LOCUS on the chromosome. Genes are involved in the control of all metabolic pathways and the synthesis of all non-protein molecules in cells. The genetic code Triplet code – every three amino acids or CODON code for an amino acid There are multiple codons for each amino acid except methionine Some codons code for ‘STOP’ The codons are widespread but not universal; genes can be used in genetic engineering to place genes in different organisms.Transcription mRNA is produced The template strand of DNA is used as a template for RNA nucleotides The hydrogen bonds between DNA bases are broken by DNA HELICASE Activated RNA nucleotides, ATP, GTP, CTP and UTP bind to their complementary nucleotides of the template strand of the gene. The extra phosphoryl groups on the activated RNA nucleotides are released, this releases energy for the nucleotides to be bonded by phosphodiester bonds.
The RNA is released from the DNA gene and passes out of the nucleus through a pore in the nucleur envelope to a ribsome.Translation Ribosomes Built up of two subunits. There is a groove down the centre that mRNA slides down to be translatedTransfer RNA Have 3 exposed bases at the end of their structure where an amino acid can bind At the other end there is an anti-codon which is complementary to the codon which codes for the next amino acid in the polypeptide sequenceHow translation occurs The first codon of the gene is always AUG, the tRNA’s anticodon then forms hydrogen bonds with the mRNA’s codon. The amino acid which it has transferred is then bonded (via peptide bond) with the next codon using ATP and an enzyme. The ribosome then moves down the mRNA…
