Protein synthesis

Question 1

Transcription - stage 1

Answer 1

RNA polymerase attaches to DNA double helix @ start of a gene
H-Bonds break and separate 2 strands and DNA uncoils, exposing some bases
one strand becomes template for mRNA copy

Question 2

Transcription - stage 2

Answer 2

RNA polymerase lines up free RNA nucleotides
free bases attracted to complementary exposed bases
RNA polymerase joins RNA bases together once RNA paired up with DNA bases forming mRNA

Question 3

Transcription - stage 3

Answer 3

RNA polymerase moves along DNA, separating strand and assembling mRNA
H-Bonds reform between uncoiled strands once RNA polymerase has passed by

Question 4

Transcription - stage 4

Answer 4

RNA polymerase reaches stop signal and detaches from DNA (stops making mRNA)
mRNA moves out of nucleus through nuclear pore and attaches to ribosome in cytoplasm for translation

Question 5

|ntrons and Exons

Answer 5

eukaryote pre mRNA requires splicing (in nucleus) to remove introns which don’t code for anything and leave the exons (which do)
prokaryotes don’t have introns in their DNA so splicing not required - mRNA goes straight to ribosome

Question 6

Translation - stage 1

Answer 6

mRNA attached to ribosome
tRNA molecules carry amino acids to it
ATP provides energy required for amino acid-tRNA bond
first tRNA molecule anticodon attaches to complementary mRNA codon, then a second

Question 7

Translation - stage 2

Answer 7

amino acids on tRNA joined by peptide bond and first tRNA molecule moves away, leaving amino acid behind. and so on with second third etc
process continues until stop signal reached on RNA molecule
polypeptide chin moves away from ribosome and translation is complete