Protein synthesis Flashcards
(7 cards)
What is transcription?
one gene on the DNA is copied into mRNA
What is translation?
mRNA joins with the ribosome and corresponding tRNA brings amino acid that codon codes for
Why is transcription necessary?
DNA is too large to leave the nuclear pores so a complementary mRNA copy of a gene on the DNA is created in the nucleus
What is the process of transcription?
1.) DNA helicase breaks the hydrogen bonds holding the bases together leaving one chain of the DNA to act as a templates
2.) free mRNA nucleotides in the nucleus are attracted and align opposite the exposed complementary DNA bases on the template strand with Thymine being replaced by Uracil
3.) RNA polymerase catalyses a condensation reaction between the RNA nucleotides forming phosphodiester bonds to create a new polymer chain - when RNA polymerases reaches a stop codon the chain is terminated and pre mRNA detaches
What is the process of splicing?
the introns are spliced out by a protein called a splicesome leaving the exon (coding regions) to join together
Why does splicing happen?
pre mRNA has to be modified to become mRNA that is ready to leave the nucleus and take part in translation
What is the process of translation?
1.) once modified mRNA leaves the nucleus it attaches to the ribosome at the start codon
2.) tRNA (attached to an amino acid) with the complementary anticodon attaches to mRNA codon (hydrogen bond)
3.) the ribosome will move along the mRNA to enable another complementary tRNA to attach to the next codon on the mRNA.
4.) the 2 amino acids that have been delivered by the tRNA are joined by peptide bonds which is catalysed by an enzyme and requires ATP
5.) first tRNA is released and can collect another amino acid
6.) continues until the ribosome reaches a stop codon at the end of mRNA and the stop codon doesn’t code for an amino acid - ribosome detaches, translation ends
many ribosomes can travel along the mRNA at the same time - polysome
