transcription and translation

Question 1

what is transcription

Answer 1

making a complementary strand of DNA in the form of pre mrna

Question 2

process of transcription

Answer 2

• an enzyme moves down the complementary bases to seperate the two strands exposing the nucleotide bases
• the nucleotide bases on the template strand pair with their complementary bases in the pool of bases present in the nucleus
• RNA polymerase then moves along the two strands to form a pre mrna molecule by joining the nucleotide pairs together.
• G joins C and adenine joins URACIL
• when RNA polymerase meets a triplet of bases that recognise a stop codon triplet the production of pre mRNA is complete.

Question 3

splicing of pre mRNA

Answer 3

spliced to produce mRNA
base pairs corresponding to introns are removed because they prevent the synthesis of polypeptides
functional exons are joined together
doesn’t happen in most prokaryotes as they don’t have introns
once they have been spliced mRNA molecules leave the nucleus via the nuclear pores.

Question 4

translation

Answer 4

• leaves through nuclear pore and binds to ribosome
• the complementary anticodon on a tRNA molecule binds to the start codon
• it brings an amino acid which attaches at other end
• another tRNA binds at next triplet, a peptide bond forms between the two amino acids
• the tRNA molecule on previous breaks down
• ribosome moves along mRNA until stop codon reached
• polypeptide formed