F215 Flashcards
Transcription
An mRNA copy of a gene is made in the nucleus;
1) transcription starts when
Polymerase chain reaction
PCR is used to make millions of copies of fragment DNA.
1) a reaction mixture is made up contains DNA SAMPLE, FREE NUCLEOTIDES, PRIMERS AND DNA POLYMERASE.
2) DNA mixture is heated 95C to break hydrogen bonds between DNA strands
3) cooled to between 50 - 65 degree to allows primers to bind to complementary base pairs at the beginning of the fragment.
4) heated to 72 degrees so that DNA POLYMERASE can work
5) DNA polymerase lines up free DNA nucleotides along side each template strand. Complementary base pairing means that new complementary strands are formed
6) two new copies are formed and one cycle of PCR is complete
7) cycle begins again when the mixture is heated to 95 degrees, and all 4 strands are used as templates
Making DNA fragments with restriction enzymes
1) some sections of DNA have palindromic sequences of nucleotides which consist of anti parallel base pairs.
2) RESTRICTION ENZYMES recognise specific palindromic sequences - known as recognition sequences - and cut the DNA at these places
3) different restriction enzymes cut at different specific recognition sequences, because the shape of the sequences is complementary to the enzyme’s active site.
4) if the recognition sequences are at either end of the desired fragment, it can be separated from the DNA fragment
5) dan sample is incubated with the specific restriction enzymes which cuts the dan fragment via a hydrolysis reaction
6) sometimes the cut leaves sticky ends - small tails of unpaired bases at each end of the fragment which can bind to DNA fragments with complementary sequences.
