DNA replication Flashcards
explain why DNA replicates ?
DNA copies itself before cell division so that each new cell has the full amount of DNA. The method is called semi-conservative replication
because half of the strands in each new DNA molecule are from the original DNA molecule. This means that there’s genetic continuity between generations of cells (i.e. the cells produced by cell division inherit their genes from their parent cells).
what is the first step of DNA replication ?
The enzyme DNA helicase
breaks the hydrogen bonds
between bases on the
two polynucleotide DNA
strands. This makes the
helix unwind to form two
single strands.
What is the second step of DNA replication ?
Each original single strand acts
as a template for a new strand.
Complementary base pairing
means that free-floating DNA
nucleotides are attracted to their
complementary exposed bases
on each original template strand
— A with T and C with G.
what is the third step of DNA replication ?
Condensation reactions join the
nucleotides of the new strand together — catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the bases on the original and
new strands.
Each new DNA molecule
contains one strand from
the original DNA molecule
and one new strand.
