DNA replication Flashcards
(27 cards)
what were the 3 theories of dna replication
conservative
semi conservative
dispersive
what is the theory of semi conservative replication
each strand of a parental double helix acts as a template for the formation of a new molecule
What is the key points of the DNA replication experiment (3)
- dna bases should contain nitrogen
- N14 is light, N15 is heavy
- bacteria uses nitrogen to make the nitrogenous bases found in DNA
what is the name of DNA replication experiment
Meselsohn-Stahl
SEMI CONSERVATIVE
each strand of a DNA molecule is used as a template for a newly synthesised strand
new DNA molecule will include 1 original strand and 1 newly synthisied strand
how many bases code for each amino acid
3
how many amino acids are there?
20
how many stop codes are there?
3
what would happen if one base coded for one amino acid
only four amino acids could be made
what would happen if two bases coded for one amino acid
16 combinations
what would happen if three bases coded for one amino acid
64 combinations which is enough for 20 amino acids
what are degenerate codes
more than one triplet code coding for the same amino acid
what is the equivilant of dna triplets in RNA
rna codons
what is a non-overlapping code
each base only appears in one triplet
what is a universal code
the same in all living organisms
definition of stop - codon code
acts as a terminating signal
defenition of degenerate code
more than one triplet code for an amino acid
what happens if theres a mutation in the DNA / m RNA
triplet code will chane which COULD change the amino acid
what parts can mutate
DNA
mRNA
exons and introns in prokaryots
mRNA directs the synthesis of the polypeptide
exons and introns in eukaryots
RNA has the be processed before it can be used to synthesise the polypeptide
what is the phase before final mRNA
pre- mRNA
what needs to be removed in pre mRNA
introns
how are introns cut off
using endonucleases
