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1.1 describe the processes involved in the transfer of information from DNA through RNA to the production of a sequence of amino acids in a polypeptide
describe the processes involved in the transfer of information from DNA through RNA to the production of a sequence of amino acids in a polypeptide
- The mRNA molecule moves through the nuclear membrane pores to attach to ribosomes in the cytoplasm. A number of ribosomes attach, in turn, to the mRNA strand and each ribosome produces one polypeptide.
- Transfer RNA (tRNA) molecules are found in the cytoplasm and carry amino acids on one end. The other end of a tRNA molecule has a complementary triplet of bases to the codons of mRNA. These tRNA triplets are called anti-codons. The anti-codon of the tRNA attaches to the codon of the mRNA. The binding of two tRNA anti-codons allows two amino acids at the opposite ends of the tRNA molecules to come together. These amino acids join together by forming a peptide bond. The tRNA molecules then detach from the mRNA and move off to pick up more amino acids. Another tRNA molecule (with its specific amino acid) then moves in and its anti-codon attaches to the codon of the mRNA and more peptide bonds join the amino acids. This continues until a “stop” codon on the mRNA dictates that the polypeptide synthesis is finished. The base sequences of the mRNA are translated into amino acid sequences in polypeptides.
More information on RNA and coding for amino acids
, AP Biology, Conestoga High School, Berwyn, Pennsylvania, USA.
Example:
DNA triplets
|
TAC |
CCG |
ATA |
TGG |
TCT |
AGC |
ATT |
mRNA codon (transcription) |
AUG |
GGC |
UAU |
ACC |
AGA |
UCG |
UAA |
tRNA anti-codon |
UAC |
CCG |
AUA |
UGG |
UCU |
AGC |
AUU |
Amino acids (translation) |
methionine (start) |
glycine |
tyrosine |
threonine |
arginine |
serine |
stop |