1.3 Flashcards
what is the structure of RNA
single stranded and is composed of nucleotides
what is stage one of transcription
RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases
stage two of transcription
as RNA polymerase breaks the bonds it synthesises a primary transcript of mRNA , these form hydrogen bonds with the exposed DNA strand by complementary base pairing
what happens in stage three of transcription
RNA splicing forms a mature mRNA transcript
how does splicing work
the introns are removed and the remaining exons are joined together
how can different proteins be expressed from one gene
alternative splicing
stage one of translation
tRNA molecules have an anticodon and a region for an amino acid to attachh
stage two of translation
mRNA molecule travels through the cytoplasm and attaches to the ribosome
stage three of translation
tRNA molecules transport specific amino acids to the ribosome
stage 4 of translation
each mRNA codon codes for a specific amino acid
stage five of translation
the first codon of an mRNA molecule is a start codon , which starts the translation
stage six of translation
the anticodon and codons match up and form complementary base pairs so the genetic code is translated into a sequence of amino acids
stage 7 of translation
peptide bonds form between the adjacent amino acids to form the polypeptide
stage 8 of translation
used tRNA molecules exit the ribosome and collect another specific amino acid
how are proteins formed
amino acids are linked by peptide bonds to from polypeptides , these chains fold to form the three dimensional shape of a protein held together by hydrogen bonds
