3.4.2 DNA and protein synthesis

mRNA function

Carries genetic code from DNA (in the nucleus) to the ribosomes (in the cytoplasm)

mRNA 3 bases are

Codon

Why does mRNA length vary?

Based on gene and protein

tRNA function

(Single RNA strand)Carries amino acids to the ribosome, where they are used to make proteins.

Importance of tRNA anticodons

Complementary to mRNA codons for specific base pairing

Importance of tRNA’s amino acid binding site

To carry amino acids

Transcription 6 steps

1.H-bonds break between nucleotides and this separates DNA strands

2.RNA nucleotides bind to DNA nucleotides by complementary base pairing

3.RNA polymerase joins the nucleotides together by phosophodiester bonds to form pre-mRNA

4.Introns (sections of non-coding nucleotides) are removed from the pre-mRNA (this is called splicing)

5. The exons are joined together to form mRNA

6. The mRNA leaves the nucleus through the nuclear pore and associates with a ribosome

Translation 8 steps

6. The mRNA leaves the nucleus through the nuclear pore and associates with a ribosome

7. The ribosome moves to find the start codon (AUG) on mRNA

8.A tRNA molecule anticodon binds to the complementary codon on mRNA

9. The ribosome moves to the next codon on mRNA and another tRNA brings another amino acid to 2nd the binding site in the ribosome (ribosomes cover 2 codons at a time)

10.Each tRNA molecule is attached to a specific amino acid which uses ATP

11. The amino acids are joined together by peptide bonds using energy from ATP

12. The first tRNA is released from the ribosome and goes to bind to another amino acid

13. The ribosome moves along to the next codon on the mRNA

Why ATP required for process?

Amino acids joined together by peptide bonds using energy from ATP