Protein synthesis 2 (transcription + translation)

Question 1

Transcription

Answer 1

1. One DNA strand is used as a template strand.
2. An enzyme RNA polymerase will use the template strand to produce an mRNA single strand, by using the complimentary base-pairing rule.
3. A pairs with T (apart from mRNA where T is replaced by U and pairs with A) and C pairs with G.
4. The coding strand has the same sequence apart from Uracil which replaces thymine in mRNA.
5. As the mRNA strand that codes for the polypeptide chain, this makes the mRNA strand complementary to the template strand.
6. This is done by the enzymes unwinding the helix and breaking hydrogen bonds (as they are weak) and attaching the gene, reads the DNA in 3’s also know as Triplets. The enzymes bring in RNA nucleotides from the nucleus to bond base on complementary base paring rule.
7. Once the enzyme has reached the terminator sequence , it stops creating mRNA. The mRNA is released and leaves the nucleus through it pores to the cytoplasm. The DNA rewinds back into a double helix.

Question 2

Transcription

Answer 2

1. The mRNA strand attaches to the ribosome.
2. The ribosomes will read a start codon (ie. AUG).
3. A codon is a series of 3 consecutive bases read on the mRNA strand.
4. While each codon is read, a tRNA molecule with the complementary sequence, an anti-codon (eg. UAC), to the mRNA codon (based on the complementary base pairing rule) binds to the ribosome and delivers its amino acid. The amino acids bond together with peptide bonds.
5. Each tRNA has a specific amino acid that attaches to it in the cytoplasm.
6. Once added, the tRNA molecule moves away allowing the next amino acid to be added, forming a polypeptide chain.
7. Translation continues until a ribosome reaches a stop codon that signals the end of translation.
8. No more amino acids are brought in and the polypeptide chain is released from the ribosomes, and the ribosome disassembles from the mRNA strand.
9. And folds into a 3-dimensional shape, becoming a functional protein.