paper 2: Gene Technology

Question 1

define genome

Answer 1

entire set of DNA in anorganism or cell

Question 2

define proteome

Answer 2

range of proteins that a cell can produce

Question 3

explain what a genome project is and how it can be used ot determine an organisms proteome

Answer 3

• genome project determins the DNA base sequence of organisms proteome
• this allows the amino acid sequences of the proteins to be determined ( the proteome)

Question 4

explain why it is easier to determine the denome and proteome of simpler organisms compared to more complex organisms

Answer 4

• easier ot determine prokaryotic DNA as it is shortter and doesnt contain introns that need to be removed by splicing
• whereas more complex organisms the non-coding DNA and regulatory genes mean that the genome cannot be easily translated into the proteome

Question 5

name one medical use of genome prjects

Answer 5

by identifying the proteome of microoganisms it allows the identification of antigens for the use of vaccine production

Question 6

define recombinant DNA

Answer 6

DNA made from 2 or more different organsims

Question 7

explain how complimentary DNA is produced using reverse transcriptase and the advantages of this method

Answer 7

method:
- in beta cells in the human pancreas
- mRNA which codes for insulin is extracted
- the mRNA acts as a template on which a cDNA is formed using reverse transcriptase
- forms single stranded DNA
- then double stranded DNA is formed using DNA polymerase and DNA nucleotides

advantage:
- use mRNA as there are no introns

Question 8

explain how DNA is cut into fragments and what enzyme is used

Answer 8

• restriction enzymes hydrolyse phosphodiester bonds at recognition sites
• these sequences are palendromic so can be read in oposite directions
• they form sticky ends

Question 9

explain the advantages of the gene machine method

Answer 9

• faster as no need to isolate DNA/RNA from cell
• any sequence of nucleotides can be made
• no introns so can be expressed by prkaryotes
• vary accurate

Question 10

define the term vector in therms of making recombinant DNA

Answer 10

vectors carry the gene into the plasmid

Question 11

explain how a DNA fragment can be inserted into a vector including the improtance of sticky ends

Answer 11

• the plasmid is cut open using the same restriction enzyme as was used to cut out the gene from the DNA
• this is so that the stciky ends on the plasmid are complimentary tot he sticky ends on the gene
• they hydrogen bond
• DNA ligase forms phosphodiester bonds to join the nucleotides of the plasmid and the gene.
• forms recombinant DNA

Question 12

explain how the DNA of the vector is introduced to host cells by transformation

Answer 12

• the DNA can enter the host cell by using calcium ions, electric shock or heat shock
• makes the membrane more porous
• or using a virus like a bacterophage

Question 13

explain what a gene marker is and how it can be used to identify which cells have taken up the recombinant DNA/gene

Answer 13

a gene marker identifies which cell has taken up the gene
- antibiotic resistance marker genes grow bacteria on a medium containing the antibiotic the plasmid is resistant to so only the cell containing the plasmids survive
- gene fourescent marker genes glow brighly under UV light

Question 14

explain why PCR is used

Answer 14

make many copies of a particular DNA base sequence from a small sample

Question 15

in PCR explain why the DNA has to be heater to 95°

Answer 15

to break the hydrogen bonds between complimentary bases causing the strands to separate

Question 16

explain in PCR why it is cooled to 55°

Answer 16

to allow primer to bind to the DNA

Question 17

explain in PCR why it is heated to 72°

Answer 17

it is the optimum temperature for heat stable DNA polymerase

Question 18

explain in PCR what the primers are for and why 2 are used

Answer 18

primers are used to mark the start and end of the gene that is to be copied

Question 19

explain how electrophoresis separates DNA and how you can identify unknown lengths of DNA

Answer 19

• DNA fragments are run on an electrophoresis gel
• DNA is negatively charged so moves towards positive electrodes
• shortest fragments move the furthest
• gel is read by lazerbeam and the sequence of colours in converted into DNA sequence

Question 20

describe what a DNA probe is

Answer 20

a short single strand of DNA that has a complimentary base sequence to the allele and thye bind to the allele and have a radioactive or flourescent label for detection

Question 21

describe the step-by-step method by which DNA probes can be used to identify the presence of a certain allele by genetic screening

Answer 21

• extract DNA using homogonisation and centrifugation
• use PCR to make many copies of DNA
• cut DNA with restriction enzymes by hydrolysing phosphodiester bonds at recognition sites
• use gel electrophoresis to separate the DNA fragments by lengths
• transfer DNA from gel to nylon mebrane ( southern blotting)
• DNA is made single stranded
• add DNA probe with a complimentary base sequence to the allele with a radioactive/ flourescent label which binds to the alle if present
• wsh the membrane to remove unbound probes and prevent false positives
• identify allele is present using autoradiography

Question 22

describe the use of genetic counselling

Answer 22

provides individuals with information regarding their probability of developing genetic disorders and probability f passing on genetic disorders to their offspring using genetic screening results.

Question 23

describe what VNTRs are

Answer 23

repeating DNA bases sequence found between genes.

Question 24

explain how genetic fingerprinting is acrried out

Answer 24

• extract DNA using homogonisation and centrifugation
• use PCR to make many copies of DNA
• cut DNA ontaininh VNTRs with restriction enzymes by hydrolysing phosphodiester bonds at recognition sites
• use gel electrophoresis to separate the DNA fragments by lengths
• transfer DNA from gel to nylon mebrane ( southern blotting)
• DNA is made single stranded
• add DNA probe with a complimentary base sequence to the VNTRs with a radioactive/ flourescent label which binds to the VNTRs if present
• wsh the membrane to remove unbound probes and prevent false positives
• identify VNTRs is present using autoradiography

Question 25

explain how the results of genetic fingerprinting are interpreted in a paternity test

Answer 25

all the bands that the child doesn’t mathc the mother must match the father

Question 26

decribe the uses of genetic fingerprinting in terms of medical diagnosis, forensic science and animal/ plant breeding.

Answer 26

medical diagnosi:
- certain tumours have certain genetic fingerprints which are different formm normla body cells so can be compared to knows types of tumour to diagnose.

forensic science:
-match suspects genetic fingerprint to DNA found at a crime scene e.g. from hair or blood sample

animla and plant breeding:
- can be used to select the least closely related orgnisms, those wo have the most different bands on their gentic fingerprint to prevent inbreeding and reduce chances of gentic disorders