6.3 Manipulating Genomes

Question 1

What is the function of the polymerase chain reaction (PCR)?

Answer 1

Allows scientists to amplify (produce lots of) DNA from a very small sample

Question 2

What are the main stages in PCR?

Answer 2

1. Separating the strands of DNA by breaking H bonds (90 - 95 degrees)
2. Annealing the primers at 3’ end of DNA which are needed for DNA polymerase to attach (55 - 68 degrees)
3. DNA polymerase adds bases to primers in 5’ -> 3’ direction (71-75 degrees)

Question 3

What is electrophoresis?

Answer 3

Used to separate DNA / proteins based on size

Question 4

What are the main stages of electrophoresis?

Answer 4

1. DNA samples treated with restriction enzymes to cut them into fragments
2. DNA samples placed in wells in negative electrode (cathode) end of gel
3. Gel immersed in tank of buffer solution and electric current passed through
4. Shorter lengths of DNA move faster and further through gel plate
5. Position of fragments can be viewed using probes

Question 5

What are the uses of DNA profiling/

Answer 5

-Forensic science
-Paternity testing
-Identifying evolutionary relationships between species
-Identifying individuals at risk of developing a certain disease

Question 6

What are DNA probes?

Answer 6

Short single stranded piece of DNA that is complimentary to a section of DNA. They are either labelled by a radioactive marker or a fluorescent marker

Question 7

What are the main stages involved in genetic engineering?

Answer 7

-Isolating the desired gene
-Putting gene into vector
-Transferring vector into host cell
-Host cell will express new gene

Question 8

How is a desired gene isolated in genetic engineering?

Answer 8

EITHER - directly from DNA where a DNA probe is used to locate the gene and it is cut out using a restriction endonuclease
OR - from mRNA where mRNA is isolated for the desired gene from cells expressing the gene. mRNA is used as a template and reverse transcriptase is used to make a single strand of complimentry DNA, primers are added and DNA polymerase to make cDNA double stranded.

Question 9

How is the gene put into a vector in genetic engineering?

Answer 9

using plasmids - plasmids are cut using the same restriction endonuclease that was used to cut out the gene. Ligase enzyme used to join plasmid and gene

Question 10

How is the vector transferred into the host cell in genetic engineering?

Answer 10

-Heat shock treatment - walls become more permeable and allow DNA in
-Electroporation - high voltage pulses used to disrupt the membrane
-Electrofusion - electric currents applied to the membrane of 2 cells to fuse the cells
-Transfection - DNA can be packaged into a a bacteriophage which is a virus that infects bacteria cells and transfers the DNA into the host cell

Question 11

What is gene therapy?

Answer 11

Inserting a functional allele of a gene into a cell that contains a non-functioning allele of that gene so a functioning protein will be produced. This is only temporary and will not be inherited and only for recessive disorders

Question 12

What is germ line gene therapy?

Answer 12

Functional allele is inserted into gametes / zygotes so all cells are altered and it will be inherited by future generations

Question 13

What is somatic gene therapy?

Answer 13

Functional alleles can be packaged into viruses / liposomes then inhaled so the functional allele will get into some of the cells lining the respiratory tract

Question 14

List some positives of genetic manipulation

Answer 14

-Can benefit human health
-Decrease starvation
-Make life saving drugs
-Reduce use of pesticides