Protein synthesis

What are the 3 types of RNA

• Messenger RNA (mRNA): Copy of DNA

• Transfer RNA (tRNA): Carries amino acids to ribosomes to be bonded to make polypeptides

• Ribosomal RNA (rRNA): Found in ribosome in the small and large subunits

Give me the steps of transcription

1. RNA polymerase attaches to the promoter region of the DNA- hydrogen bonds between the 2 DNA strands break and exposes the template strand for complementary base pairing with free RNA nucleotides

2. RNA uses template (antisense) strand to build complimentary RNA strand based on the DNA strand

3. RNA polymerase catalyses the addition of complementary bases on strand RNA nucleotides to form an mRNA strand. Phosphodiester bonds form between RNA nucleotides.

4. mRNA then detaches from antisense strand and leaves through nuclear pores

Note:

Remember in RNA T is replaced with U

What are the steps of translation

1. mRNA moves out of nucleus through a nuclear pore and attaches to ribosome

2. tRNA molecules, have a specific anticodon complementary to the codon on the mRNA strand, and delivers its specific amino acid to the ribosome ensuring the correct order of amino acids according to the mRNA code

3. Amino acids are joined with peptide bonds to form the primary structure of the polypeptide

Tell me the differences between protein synthesis and DNA replication

Similarities:

• DNA unwinds and unzips

• Complementary DNA is involved

• There is hydrogen bonds

• Same enzyme involved to catalyses synthesis of nucleotides polymerase

• Both are making copies of DNA

Differences:

• Only a small section of DNA unzips during transcription

• Both strands act as a template in replication

• mRNA leaves nucleus whilst new strand is bound to nucleus

• Two strands are made in replication

• RNA polymerase in protein synthesis, DNA polymerase in replication

• Replication has helicase