UrwaMesret

3.5 Bio notes

Transcription is where the gene is converted into a mRNA messenger which is posted to the ribosomes which occurs in nucleus.

Translation occurs when ribosomes translate the message into a polypeptide which occurs in the cytoplasm.

The sequence of amino acids is determined by the genes which are codes for making polypeptide.

DNA – double helix & Thymine pairs with Adenine

RNA- single strand & bases Uracil replaces Thymine

Transcription is where a polymerase makes a mRNA molecule that is complementary to the DNA.

Translation is where mRNA is posted out of the nucleus and attaches to ribosomes. Ribsomes use complementary base-pairing to ‘read’ codons on the

mRNA. tRNA transfer molecules with corresponding anti- codons bring the correct amino acid.

DNA is transcribed in triplets- sequence of three bases which gives mRNA codons- sequence of three RNA bases. mRNA codons make up genetic code.

The genetic code: all living things use the same code and same bases. Codons code for the same amino acids. There are 64 codons but 20 amino acids.