7.1 Flashcards
what are exons
coding regions of DNA
what are introns
large non-coding areas of DNA that are removed before mRNA is transcribed
what is DNA/gene sequencing
the analysis of the individual base sequence along a DNA strand or an individual gene
what is DNA profiling
analysis of the repeating patterns in the non-coding areas of DNA
what does PCR stand for
polymerase chain reaction
define PCR
the reaction used to amplify a sample of DNA to make more copies of it rapidly
what is amplification
repeated replication using PCR to produce a bigger sample
how does PCR work
- sample is mixed with enzyme taq, DNA polymerase, primers, nucleotide bases and a buffer
- it is then placed in the PCR machine where it is heated to 90’-95’ causing DNA strands to separate as hydrogen bonds are broken
- it’s then cooled to 50’-55’ so that the primers can anneal
- then its heated to 72’ so that taq and DNA polymerase can build a complementary strand of DNA
what are primers
small sequences of DNA that must join to the beginning of the separated DNA strands before copying can begin
what is the general process of gene sequencing
- DNA strands are chopped into smaller pieces
- double strands separate into single strands
- PCR replicates fragments for analysis
- labelled terminator bases are added to the single strands to stop DNA synthesis
- these coloured tags allow the sequence to be read rapidly
what are terminator bases
modified versions of the four nucleotide bases that stop further DNA synthesis
what are gene variants
different versions of a gene
what is siRNA
small inferring RNA
coded for in non-coding regions of DNA
they interact with mRNA to prevent production of certain proteins
what are micro-satellites
a section of DNA with a 2-6 base sequence repeated 5 - 100 times
what are mini-satellites
section of DNA with a 10 -100 base sequence repeated 50 - several hundred times
How is DNA prepared for DNA profiling
strands of DNA are cut into fragments via restriction endonuclease which cuts the DNA at particular points in the intron called recognition sites either side of mini and micro satellites
How is gel electrophoresis carried out
DNA fragments are placed in wells in agarose gel medium with a known buffer solution and known DNA fragments
the gel contains a dye which will bind to the DNA fragments and fluoresce as well as a visible dye that moves faster than the DNA
an electrical current is passed through the apparatus and DNA fragments move towards positive anode at different rates depending on size and charge
once its complete it is put under uv light so the fragments can be identified
what is southern blotting
DNA fragments are drawn from electrophoresis gel to a filter leaving blots on the filter and denaturing the fragments so that the bases are exposed
how is southern blotting carried out
an alkaline buffer solution is added to the complete gel electrophoresis and a nylon filter is placed over it then the fragments leave blots on the filter and the alkaline buffer denatures the fragments to leave exposed bases
what are gene probes
short DNA sequences fluorescently labelled which are complementary to DNA sequences
what is hybridization
the binding of a gene probe to its complementary strand
what are short tandem repeats
micro-satellite regions used in DNA identification
