DNA Flashcards
DNA definition
the chemical used to encode genetic information for most known life forms
Who discovered DNA?
Watson and Crick (but they discredited Rosalind Franklin)
What is DNA’s shape?
double-helix
Nucleotide
composed of three parts –
phosphoric acid,
pentose sugar,
a nitrogen containing base (A,C,T,G)
What are the complementary base pairings?
A-T : form two hydrogen bonds
G-C : form three hydrogen bonds
DNA Replication definition
semi-conservative
– the double stranded nature of DNA allows for each strand to serve as a template for each copy of DNA
1st Major Event of DNA Replication
DNA helicase unwinds double stranded DNA
2nd Major Event of DNA Replication
New complementary DNA nucleotides are fit into place and joined by DNA polymerase
3rd Major Event of DNA Replication
Antiparallel configuration means synthesis occurs in opposite directions
(leading strand follows helicase enzyme, lagging strand forms okazaki fragments)
4th Major Event of DNA Replication
DNA ligase seals and breaks in the sugar-phosphate backbone, and DNA returns to its coiled structure
5th Major Event of DNA Replication
The two double helixes are identical to the original DNA membrane
DNA polymerase works very _____
rapidly (about 50 nucleotides per second)
Replication errors ______
do occur (1/100,000,000 nucleotides)
What happens when an error does occur?
an enzyme will usually fix it
What happens if an enzyme doesn’t fix the error?
It becomes a mutation (which is a source of novel diversity in populations)
