7.1

Question 1

what are exons

Answer 1

coding regions of DNA

Question 2

what are introns

Answer 2

large non-coding areas of DNA that are removed before mRNA is transcribed

Question 3

what is DNA/gene sequencing

Answer 3

the analysis of the individual base sequence along a DNA strand or an individual gene

Question 4

what is DNA profiling

Answer 4

analysis of the repeating patterns in the non-coding areas of DNA

Question 5

what does PCR stand for

Answer 5

polymerase chain reaction

Question 6

define PCR

Answer 6

the reaction used to amplify a sample of DNA to make more copies of it rapidly

Question 7

what is amplification

Answer 7

repeated replication using PCR to produce a bigger sample

Question 8

how does PCR work

Answer 8

• 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

Question 9

what are primers

Answer 9

small sequences of DNA that must join to the beginning of the separated DNA strands before copying can begin

Question 10

what is the general process of gene sequencing

Answer 10

• 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

Question 11

what are terminator bases

Answer 11

modified versions of the four nucleotide bases that stop further DNA synthesis

Question 12

what are gene variants

Answer 12

different versions of a gene

Question 13

what is siRNA

Answer 13

small inferring RNA
coded for in non-coding regions of DNA
they interact with mRNA to prevent production of certain proteins

Question 14

what are micro-satellites

Answer 14

a section of DNA with a 2-6 base sequence repeated 5 - 100 times

Question 15

what are mini-satellites

Answer 15

section of DNA with a 10 -100 base sequence repeated 50 - several hundred times

Question 16

How is DNA prepared for DNA profiling

Answer 16

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

Question 17

How is gel electrophoresis carried out

Answer 17

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

Question 18

what is southern blotting

Answer 18

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

Question 19

how is southern blotting carried out

Answer 19

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

Question 20

what are gene probes

Answer 20

short DNA sequences fluorescently labelled which are complementary to DNA sequences

Question 21

what is hybridization

Answer 21

the binding of a gene probe to its complementary strand

Question 22

what are short tandem repeats

Answer 22

micro-satellite regions used in DNA identification