Protein Synthesis Flashcards
1
Q
Where does transcription occur and what does it involve?
A
Occurs in the nucleus and involves copying the DNA code
2
Q
Where does translation occur and what does it involve?
A
Occurs in the cytoplasm and it involves ribosomes joining amino acids together to form polypeptides
3
Q
Describe the process of transcription.
A
- DNA Helicase breaks hydrogen bonds causing the double helix to unwind and separate the two polynucleotide strands
- Only one of the strands acts as a template
- Free RNA nucleotides line up alongside the exposed DNA bases and form complementary base pairs with hydrogen bonds
- Uracil lines up alongside an exposed Adenine
- Adjacent RNA nucleotides are then joined together by phosphodiester bonds in condensation reactions by RNA polymerase to form pre-mRNA
- pre-mRNA molecules is then spliced to form mRNA which includes exons only.
- mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm
4
Q
Describe the process of splicing pre-mRNA.
A
- Pre-mRNA is made up of exons which do code and introns which don’t code.
- Introns are cut out by restriction endonuclease and exons are joined together by ligase
- mRNA is produced which is shorter than pre-mRNA
5
Q
Describe the process of translation.
A
- Each tRNA molecule has a specific amino acid attached and three exposed bases known as an anticodon.
- Two tRNA molecules with complementary anticodons to the first and second codons on the mRNA strand move to the ribosome carrying specific amino acids
- The amino acids are joined together by a peptide bond in a condensation reaction
- This requires the use of ATP and an enzyme
- The first tRNA molecule then detaches from its amino acid and moves away from the ribosome
- It collects another molecule of the same amino acid from the amino acid pool in the cytoplasm
- The ribosome moves along the mRNA strand to form peptide bonds between amino acids until it reaches a stop codon
