13. translation, genetic code and tRNA Flashcards
what is the definition for the genetic code (word for word)
the set of rules by which information encoded in genetic material (DNA or RNA) is translated into amino acid sequences
what is a codon?
a triplet code in which three nucelotides make up a code-word for ONE AMINO ACID
what direction are codons read in?
from the 5’ end to the 3’ end (same direction as the synthesis of the RNA)
what does redundancy mean? how many codons and amino acids are there?
some amino acids are encoded by more than one codon. eg ‘car’ and ‘automobile’ mean the same. there are 64 codons, 61 of them code for amino acids but there are only 20 amino acids
what does it mean that the ‘genetic code is nearly unviersal’? why is this importnat - two points
codons have the same meaning in all living systems, which is imporntant as it suggests all living things are related to one another. also genes can be moved from one species to another and keep the same meaning
how do amino acids interact with mRNA codons? what is the function of this molecule?
with transfer RNAs (tRNA). tRNAs function is to transfer amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome
how does the shape of the tRNA relate to its function?
tRNA has a specific amino acid at one end, while at the other end a nucelotide triplet that can base pair with the codon on the mRNA. this means a mRNA molecule that approaches the ribosome, an amino acid sequence can be added onto a polypeptide chain because the tRNA read a triplet codon on the mRNA - translated languages
what are tRNA molecules made out of? how does this affect their strucure
single rNA strand that is about 80 nucleotides long, therefore the nucleotide bases hydrogen bond with each other and form a three dimentional sturcure
what is aminoacyl-tRNA? how do they help in translation?
aminoacyl-tRNA is an enzyme that helps with the correct matching up of tRNA and amino acids. the active site of each aminoacyl-tRNA fits only a specific combination of amino acids and tRNA. ATP catalyses the covalent bonding of the amino acid to its specific tRNA
STUDY IMAGE
what is amino acid activation? 3 steps
the attachment of an amino acid to its tRNA. amino acid reacts with ATP, which results in AMP group (ATP minus two phosphate groups).
the amino acid-AMP complex reacts with the tRNA, so the AMP group is replaced by the tRNA
energy from ATP then used in polypeptide synthesis
define what wobble is
flexible base pairing of the third codon position. because there are codons that mean the same thing in the third nucleotide base, NOT ANY OTHER POSITIONS
