21.1 DNA profiling and PCR

Question 1

what is the genome?

Answer 1

all of the genetic material an organism contains

Question 2

what is a VNTR?

Answer 2

variable number tandem repeats

short sequences of DNA which are repeated many times within introns

Question 3

what is a STR?

Answer 3

SHORTER sequences of DNA which are repeated many times

Question 4

trend in the differences in repeats

Answer 4

different people have a different number of repeats so a different satellite pattern

Question 5

what does DNA profiling do?

Answer 5

allow you to identify an individual and determine familial relationships

Question 6

when is DNA profiling used?

Answer 6

forensics
family genetics
medical diagnosis

Question 7

forensics

Answer 7

used to profile blood to link DNA on a crime scene to the DNA of suspects

Question 8

medical diagnosis

Answer 8

allows you to identify mutations

Question 9

first step of DNA fragmentation

Answer 9

extract the DNA
but not a lot of DNA
therefore PCR is done to replicate DNA to get more copies

Question 10

second step of DNA fragmentation

Answer 10

enzymes are used to cut the DNA at specific sites to create different fragments

Question 11

what enzymes are used to cut up the DNA sample into fragments?

Answer 11

restriction endonuclease

Question 12

what are the sites at which restriction endonucleases cut at?

Answer 12

the restriction site

Question 13

what happens to the VNTRs after fragmentation?

Answer 13

they stay in the same positions in the DNA fragments

Question 14

what technique is used to separate cut fragments of DNA?

Answer 14

electrophoresis

Question 15

what is gel electropheresis?

Answer 15

technique which utilises the way charged particles can move through a gel medium using an electrical current

Question 16

what gel is used in electrophoresis?

Answer 16

agarose

Question 17

how is the current induced on a gel plate?

Answer 17

the wells containing the DNA fragments are found at the negative end

the other side has the positive end

Question 18

what is the gel immersed in to separate the DNA strands?

Answer 18

in alkali

Question 19

why does the DNA move up the gel plate?

Answer 19

DNA is negatively charged and is therefore repelled by the negatively charged bottom of the plate upwards
AND
attracted by the positively charged top

Question 20

how are the DNA fragments separated in electrophoresis?

Answer 20

the smaller fragments move to the positive electrode QUCKER

the larger fragments move to the positive electrode SLOWER

means that larger and smaller fragments are spread out

Question 21

why is alkali added to the gel?

Answer 21

to turn the DNA into single strands

Question 22

what type of blotting is done to the DNA strands?

Answer 22

southern blotting

Question 23

what is southern blotting?

Answer 23

a nylon sheet is used to soak up the data onto a paper

Question 24

what are the 2 types of DNA probes?

Answer 24

radioactive
fluorescent

Question 25

how do the DNA probes bind to the DNA?

Answer 25

they are complimentary to the base sequence of the DNA

Question 26

what is used in electrophoresis to identify DNA fragments?

Answer 26

a DNA ladder

Question 27

how are the results seen using radioactive probes?

Answer 27

by using an X-ray

Question 28

how are the results seen using fluorescent probes?

Answer 28

UV light is used and the probes glow

Question 29

what is the PCR version of DNA?

Answer 29

an artificial replication of DNA from a small sample to produce a large sample

Question 30

what is a PCR machine called?

Answer 30

a thermal cycler

Question 31

step 1 in PCR

Answer 31

95 degrees the hydrogen bonds in the DNA fragment are broken by a high temperature which separates DNA into two strands

Question 32

step 2 in PCR

Answer 32

55 degrees the DNA primers anneal to the ends of the separated DNA strands

Question 33

step 3 in PCR

Answer 33

72 degrees (optimum for polymerase) DNA polymerase used to attach complimentary nucleotides starting from the DNA primer DNA polymerase forms phosphodiester bonds between adjacent nucleotides

Question 34

product of PCR after the first cycle?

Answer 34

four strands of DNA so 2 DNA molecules

Question 35

what DNA polymerase is used for the synthesis of the DNA in PCR?

Answer 35

Taq polymerase

Question 36

why is Taq polymerase thermophilic?

Answer 36

high temperatures cannot denature Taq polymerase hence it is useful in PCR where temperatures are high allows PCR to continually happen without needing to replace enzymes

Question 37

what does DNA ligase do?

Answer 37

make phosphodiester bonds

Question 38

how is PCR done with RNA fragments?

Answer 38

same process as with DNA

Question 39

how is PCR done with proteins?

Answer 39

as proteins can be positively and negatively charged, a chemical needs to denature the protein to ensure all the proteins have the same charge

Question 40

what is different about the genomes of different humans?

Answer 40

the NON-CODING regions VNTRs are many repeats of introns which are unique to humans allows use to compare the genomes of humans coding regions are much similar between humans