DNA replication Flashcards
What unzips DNA into 2 separate strands (nucleotides)?
DNA helicase (an enzyme)
What is a phosphodiester bond?
Covalent bond between phosphate group and carbons of sugars, result of a condensation reaction (ester bond).
Joins phosphate groups to sugars.
How does the enzyme DNA helicase unzip the double helix DNA?
It travels along the DNA backbone catalysing reactions that break the hydrogen bonds between the complementary base pairs.
What happens after the unzipping of DNA?
Free nucleotides line up with old nucleotides, these new nucleotides are only held by hydrogen bonds between bases, no phosphodiester bonds.
Difference between activated and normal nucleotides?
Activated nucleotides contain 3 phosphate groups rather than one.
No phosphodiester bonds in activated nucleotides like in normal nucleotides.
What does DNA polymerase do to the activated nucleotides?
Catalyses the formation of phosphodiester bonds between the activated nucleotides.
Difference between the nucleic acids RNA and DNA
.DNA is usually double-stranded and RNA is usually single stranded
.DNA contains the sugar Deoxyribose and RNA contains the sugar Ribose
.The base thymine is replaced by uracil in RNA, A bonds with U
.DNA found in chromosomes in the nucleus, RNA found in the cytoplasm (this is for eukaryotic cells)
Difference between deoxyribose and ribose
Ribose contains OH and Deoxyribose contains H, de means remove.
Oxygen is removed at second carbon in deoxyribose.
What does DNA ligase do?
Seals the cut between okazaki fragments
In what direction does DNA polymerase travel?
From the 3’ end to the 5’ end
Why does DNA polymerase not catalyse the joining of okazaki fragments?
The enzymes are substrate specific, DNA polymerase enzymes are used to join nucleotides, nucleotides have a different shape to okazaki fragments.
What is degenerate code?
Multiple codons can code for the same amino acid
3 different types of mutation:
Insertion, deletion, substitution
What effect does insertion and deletion have?
Frameshift mutation occurs, changes the codons further on in the DNA sequence
