DNA replication Flashcards
The semi conservative replication of DNA ensures…
genetic continuity between generations of cells.
Why is DNA replication described as ‘semi conserved’?
When DNA is replicated it forms daughter DNA: one strand is from the parental DNA and one strand is newly synthesised.
Where does DNA replication occur?
In the nucleus
In what part of the cell cycle is DNA replicated?
The S-phase.
How is DNA replicated?
- DNA helicase breaks H bonds between complementary base pairs between the two strands of DNA
- double helix unwinds and strands are separated, forming a replication fork
- separated parental DNA strands act as a template
- free nucleotides within the nucleus are attracted to their complementary base pairs on the template strand
- DNA polymerase catalyses the joining together of adjacent nucleotides via condensation reactions in the 5’ to 3’ direction
- this forms phosphodiester bonds to create the sugar-phosphate backbone of the new DNA strand
- two new daughter DNA strands are now formed
What is the role of DNA helicase in DNA replication?
- catalyses the reactions that unzip the DNA double helix
- breaks the hydrogen bonds between complementary bases
What is the role of DNA polymerase in DNA replication?
- catalyses the condensation reactions that form phosphodiester bonds between adjacent DNA nucleotides in the 5’ to 3’ direction
- forms a polynucleotide
What is the role of DNA ligase in DNA replication?
Catalyses the reaction that joins two nucleic acid fragments.
Which direction are nucleic acids synthesised?
5’ to 3’
What did Watson and Crick discover with the help of Rosalind Franklin’s research on x-ray diffraction?
The structure of DNA
What did Watson and Crick hypothesis about DNA?
That DNA must replicate conservatively or semi-conservatively.
Who are Meselson and Stahl and what did they do?
Two scientists who conducted an experiment to see whether DNA is replicated conservatively or semi-conservatively.
What did Meselson and Stahl find?
That DNA replication is semi-conserved.
- proved Watson and Crick’s hypothesis
