B3 Revision:Protein Synthesis
DNA controls production of proteins in a cell
Proteins made of a chain of amino acids which fold up to give each protein a specific shape and function
Gene
A section of DNA that codes for a specific protein
Order of the bases in a gene decides the order of amino acids in a protein
Amino acids coded for by a sequence of 3 bases in a gene:Base triplet
Non-coding regions of DNA
Don't code for any amino acids
Some can switch genes on and off so controls if a gene is expressed
Mutations:
Random changes to an organism's DNA which can be inherited
Produces a genetic variant (different version of a gene)
May change amino acid which may change the shape of the final protein
Causes a change in activity which could change characteristics of an organism
Process:
Transcription
Translation:
DNA can't move out of the nucleus as it's really big
RNA polymerase joined RNA nucleotides to make mRNA
RNA polymerase binds to a region of non-coding DNA in front of a gene causing the DNA to unzip
RNA polymerase moves along one of the strands of DNA
Uses coding DNA in the gene as a template to make mRNA so that mRNA complements the gene
mRNA moves out of nucleus and joins with a ribosome in the cytoplasm
After transcription
Amino acids brought to ribosome by tRNA (transfer)
Order in which they are brought matches the order of base triplets in mRNA
The pairing of the codon and anticodon makes sure the amino acids are brought to the ribosome in the correct order
Amino acids are joined together by the ribosome making polypeptide (protein) and empty tRNA move away
Codon (mRNA)
Anticodon (tRNA structure)
Base triplets in mRNA
Complimentary to codon for amino acid
Variants in non-coding regions of DNA can also affect phenotype of an organism
Variants in non-coding parts of DNA affect the ability of RNA polymerase to bind to it, making it easier or harder
Affects how much mRNA is transcribed so how much protein is produced which could affect the phenotype