Protein Synthesis

Question 1

Outline Translation process

Answer 1

mRNA leaves the nucleus and binds to a ribosome. Codons are read by the ribosome and complementary anticodons from tRNA molecule pair with these codons. The amino acids attached to the tRNA molecule are added to the growing polypeptide chain through a CONDENSATION POLYMERISATION reaction. Once all codons are read, the polypeptide chain is released and is then folded into a 3D protein shape.

Question 2

Outline transcription process.

Answer 2

RNA polymerase binds to a strand of DNA and runs along it in a 5’-3’ direction, making copies of each nucleotide read, producing an mRNA molecule. Once moving past all coding regions, the RNA polymerase encounters a stop signal of mRNA synthesis.

Question 3

Difference between RNA and DNA

Answer 3

RNA is single stranded, DNA is double stranded, RNA has the base nucleotide Uracil as opposed to Thymine in DNA, and RNA has a ribose sugar whilst DNA has a deoxyribose sugar.

Question 4

Post Transcription Modification

Answer 4

5’ end of mRNA is capped with an start codon, preventing enzyme attack
3’ end has a poly-A tail added, contributing to its stability
Spliceosomes splice out introns and splice exons together

Question 5

Lac Operon components

Answer 5

Promoter (binding site for RNA polymerase)

Operator (Where repressor binds to, regulating gene expression)

Question 6

Lac Operon with no lactose present

Answer 6

Repressor binds to operator, stopping RNA polymerase from transcribing the gene

Question 7

lactose present

Answer 7

Lactose itself binds to repressor, changing the repressor’s shape and inactivating it so it cannot bind to operator and RNA polymerase can transcribe the gene.