DNA and proteinsynthesis

Question 1

similarities in structure between mRNA and tRNA

Answer 1

• both contain the same bases

Question 2

differences in structure between mRNA and tRNA

Answer 2

• mRNA has linear structure, tRNA has clover leaf structure
• mRNA possesses codons, tRNA possesses anti-codons
• mRNA has no amino acid binding site, tRNA does

Question 3

what are introns and exons

Answer 3

• exons are base sequences in genes that code for amino acids
• introns are base sequences present within genes that do not code for amino acids

Question 4

what is a genome and proteome

Answer 4

genome-complete set of genes in a cell.

proteome-full range of proteins that a cell is able to produce.

Question 5

describe the process of transcription

Answer 5

• the relevant section containing the gene uncoils and is unzipped by DNA helicase as the hydrogen bonds break
• one of the two strands act as a template as free RNA nucleotides line up alongside the DNA nucleotide bases on the template by complementary base pairing
• free RNA nucleotides are then joined together with phosphodiester bonds in reactions catalysed by RNA polymerase producing pre mRNA

Question 6

describe the process of translation

Answer 6

• mRNA attaches to the ribosome in the cytoplasm and a tRNA molecule with the complementary anticodon base sequence binds to the first codon on the mRNA strand at the ribosome, ribosome has two binding sites so two tRNA molecules will bind to two codons on the mRNA within a ribosome.
• the amino acid on the 1st tRNA molecule is attached to the 2nd amino acid by a peptide bond in a condensation reaction
• the 1st tRNA molecule leaves the ribosome, leaving the amino acid behind and collects another molecule of the same amino acid from the ‘amino acid pool’ in the cytoplasm
• the ribosome moves along the mRNA strand until all codons have been read up to the stop codon and the polypeptide has been produced. It then folds itself into its secondary and tertiary structures.