structure & replication of DNA 1.2 Flashcards
what are DNA strands composed of
repeating units called nucleotides
what does each nucleotide consist of
a deoxyribose sugar, a phosphate group and a base
how are the deoxyribose sugar and the phosphate group held together
a chemical bond
what does the repeating nucleotides make up
the sugar phosphate backbone
DNA replication stage 1
DNA is unwound and the weak hydrogen bonds between bases are broken to form two template strands
DNA replication stage 2
DNA is replicated by DNA polymerase which needs primers to start replication
DNA replication stage 3
a primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing DNA polymerase to add DNA nucleotides
DNA replication stage 4
DNA polymerase adds DNA nucleotides using complementary base pairs to the deoxyribose 3’ end of the new DNA strand which is forming
DNA replication stage 5
DNA polymerase can only add nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments
DNA replication stage 6
fragments of DNA are joined by ligase
requirements of DNA replication
DNA template strands, primers, a supply or DNA nucleotides, DNA polymerase and ligase enzymes and ATP
what is PCR
a technique used to amplify a region of DNA
PCR stage 1
DNA is heated up to between 92 and 98°C to separate the two strands
PCR stage 2
the two strands are then cooled down to between 50 and 60°C to allow primers to bind to specific target sequences
PCR stage 3
it is then heated between 70 and 80°C for heat resistant DNA polymerase to replicate a region of DNA
