3.10 - Protein Synthesis

Question 1

What does tr inscription produce and where does it occur?

Answer 1

Produces mRNA
Occurs in nucleus

Question 2

Outline the process of transcription

Answer 2

1. Part of the DNA molecule unwinds - hydrogen bonds between complimentary base pairs break
2. The exposed gene can then be transcribed
3. A complimentary copy of the code from the gene is made by building a single stranded nucleic acid known as mRNA
4. Free RNA nucleotides pair up via Hydrogen bonds with their complimentary bases on one strand of the unzipped DNA molecule
5. Sugar phosphate groups of these RNA nucleotides are then bonded together by phosphodiester bonds by the enzyme RNA polymerase to firm the sugar phosphate backbone of the mRNA molecule
6. When the gene has transcribed the hydrogen bonds between the mRNA and DNS strands break and the double stranded DNA molecule re-forms
7. The mRNA molecule then leaves the nucleus via a pore in the nuclear envelope

Question 3

Where does transcription occur?

Answer 3

In the nucleus of the cell

Question 4

What does translation produce and where does occur?

Answer 4

Produces proteins
Occurs in cytoplasm on ribosomes

Question 5

Outline the process of translation

Answer 5

1. mRNA molecule attaches to a ribosome
2. In the cytoplasm there are free molecules of tRNA
3. tRNA molecules have a triplet of unpaired bases at one end known as a anticodon and a region where a specific amino acid can attach to at the other
4. tRNA molecules bind with their specific amino acids and bring them to the mRNA molecule on the ribosome
5. Triplet of bases on each tRNA molecule pairs with a complimentary triplet codon on the mRNA molecule
6. Condensation reactions between amino acids on tRNA form peptide bonds - requires energy from ATP hydrolysis
7. Process continues until a stop codon on the mRNA molecule is reached
8. The amino acid chain then firms a final polypeptide

Question 6

What is a mutation?

Answer 6

An alteration to the DNA base sequence