1.2 Flashcards
What is the structure of a DNA nucleotide
nucleotides are made up of:
deoxyribose sugar (3’ end)
a phosphate (Carbon 5) (5’ end)
a base (Carbon 1) (Adenine, Thymine, Guanine or Cytosine)
What is the structure of DNA
DNA is made up of 2 strands of nucleotides twisted into a double helix
It has a sugar-phosphate backbone due to bonds forming between the phosphate of one nucleotide and the carbon 3 of the deoxyribose on another nucleotide
What is the relationship between both strands of DNA
The 2 strands are held together by hydrogen bonds and have an antiparallel structure
When is DNA replicated and why
Before cell division so that every daughter cell will inherit an identical copy of the DNA
Describe the process of DNA replication
DNA is unwound and unzipped as the weak hydrogen bonds break and the bases are exposed
A primer binds to the 3’ end of the template DNA strand to start replication
The leading strand is synthesised by DNA polymerase continuously in a 5’ to 3’ direction.
The lagging strand is synthesised in fragments because it is antiparallel to the leading strand and DNA polymerase can only add DNA nucleotides in a 5’ to 3’ direction.
The fragments are then sealed together by ligase.
The 2 new strands twist to form double helixes. Each is identical to the original strand.
What is PCR
PCR amplifies DNA using complementary primers for specific target sequences
What are the steps of PCR
DNA is heated to between 92 and 98°C to separate the strands.
It is then cooled to between 50 and 65°C to allow primers to bind to the 3’ end of target sequences.
It is then heated to between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.
What are practical applications of PCR
Amplified DNA is used to diagnose genetic disorders,
settle paternity suits and to help solve crimes
