what allows DNA to code for protein synthesis Flashcards
(15 cards)
Does DNA code for polypeptides first in order for protein synthesis to occur
Yes , this is essential because proteins are made of one or more polypeptide chains
Name 5 ways in which RNA is structurally different from DNA
-sugar molecule in each nucleotide is ribose
-the nitrogenous base uracil replaces thymine
-the polynucleotide chain is usually single-stranded and shorter
-there are three forms of RNA - messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).
Where are genes found
each chromosome in a eukaryotic cell nucleus includes a molecule of DNA. On each chromosome, there are specific lengths of the DNA called genes.
What does each gene contain
Within each gene there is a sequence of DNA base triplets that determines the amino acid sequence, or primary structure, of a polypeptide.
What is crucial for a polypeptide to fold right and be held in its tertiary structure or shape
The primary structure of a polypeptide must be correct
What does the polypeptide folding right and being held in its tertiary structure or shape allow it to do
Allow it to carry out its function
Functions: What role do polypeptides play in enzymes if they fold right and make proteins
-Makes the shape of the active site of an enzyme molecule complementary to the shape of the substrate molecule
Functions: What role do polypeptides play in antibodies if they fold right and make proteins
-Makes part of an antibody molecule have a shape complementary to that of the antigens on the surface of an invading pathogen
Functions: What role do polypeptides play in receptors if they fold right and make proteins
-Makes a receptor on a cell membrane have a shape complementary to the shape of the cell-signalling molecule, such as a hormone, that it must detect.
Functions: What role do polypeptides play in ion channel proteins if they fold right and make proteins
-an ion-channel protein must have hydrophilic amino acids lining the inside of the channel, and lipophilic amino acids on the outside portion that will be next to the lipid bilayer of the plasma membrane.
How many possible combinations are in the triplet code
Three bases= one amino acid so the possible amino acids are (4x4x4) which is 64. The number used is 4 because there are 4 possible bases.The reason the number is bigger than the 20 possible amino acids is because ,for example ,two different triplet codes can code for the same amino acid.
Where are genes
Inside the cells nucleus but proteins are made in the cytoplasm in the ribosomes .
What does it mean when the nature of genetic code is described as universal
in almost all living organisms , the same triplet/triplets of DNA bases code for the same amino acid.
What does it mean when the nature of the genetic code is described as degenerate
for all amino acids, except methionine and tryptophan, there is more than one base triplet. This may reduce the effect of point mutations, as a change in one base of the triplet could produce another base triplet that still codes for the same amino acid.
What does it mean when the nature of the genetic code is described as non overlapping
it is read starting from a fixed point in groups of three bases. If a base is added or deleted then it causes a frame shift, as every base triplet after that, and hence every amino acid coded for, is changed.
