6.1.3 Manipulating Genomes

Question 1

What is DNA sequencing ?

Answer 1

Identifying the base sequence of a DNA fragment

Question 2

How have DNA sequencing methods changed over time ?

Answer 2

•It used to be manual now it is automated
•Much faster now, entire genomes can be mapped.

Question 3

Give some advantages for genome-wide comparisons

Answer 3

•Comparing between species allows us to compare evolutionary relationships
•Comparing between individuals of the same species allows us to develop more effective medicines.

Question 4

How can DNA sequencing be used in synthetic biology ?

Answer 4

•Knowing the base sequence of a gene allows us to predict the chain of amino acids it will create (polypeptide)
•This allows us to progress further in synthetic biology

Question 5

What is DNA profiling ?

Answer 5

Identifying the unique areas of a persons DNA in order to create a profile that is specific for them

Question 6

Give uses of DNA profiling

Answer 6

•Forensics - DNA obtained from a crime scene can be compared to that of suspects
•Medicine - screening for a particular base sequence in order to identify heritable diseases.

Question 7

How can we amplify DNA fragments in order to sequence them ?

Answer 7

Using polymerase chain reaction (PCR) allows us to make millions of copies of a fragment, which can then be cut at different lengths in order to be sequenced

Question 8

Describe the reaction mixture in the first stage of PCR

Answer 8

Contains the DNA fragment which will be amplified, two primers complementary to start/end of fragment, free nucleotides for the exposed bases and TAQ/DNA polymerase

Question 9

Summarise the process of amplifying DNA fragments using PCR

Answer 9

•Heat to 90’C to break apart DNA strands
•Cool to x’C to allow primers to bind
•Heated again to activate TAQ polymerase and allow nucleotides to join
•New DNA can then act as a template for next cycle.

Question 10

How is gel electrophoresis used in DNA profiling ?

Answer 10

•DNA fragments of varying lengths are placed at one end of a slab of gel
•Electrical current is applied, fragments move towards anode (DNA is -ve)
•Shorter fragments travel further, the pattern of bands created is specific to every individual.

Question 11

What is meant by genetic engineering ?

Answer 11

•Where a DNA fragment from one organism is inserted into the DNA of another organism, sometimes across different species
•This is done through the use of a vector and a host cell.

Question 12

Summarise the process of isolating a DNA fragment

Answer 12

•Restriction enzymes cut DNA at specific sequences : different REs cut at different points but the same RE cuts at the same point
•Therefore using specific REs allows us to cut out a specific DNA fragment.

Question 13

Summarise the process of inserting DNA fragment into a vector

Answer 13

•A plasmid (DNA from bacteria) is used as the vector, and is cut out using the same restriction enzymes so that the sections are complementary
•DNA ligaments joins the fragment and the plasmid together.

Question 14

Summarise the process of inserting a vector into a host cell

Answer 14

The host cells (bacteria) are mixed with the vectors in an ice-cold solution , then heated and shocked (electroporation) to increase the permeability of the cells and encourage vector uptake.

Question 15

Give some issues around genetic engineering

Answer 15

Pros
•Insect resistance introduced to crops
•GE animals used to produce pharmaceuticals
•GE pathogens can be produced for research
Cons
•GE seeds would be hard to acquire for poor farmers
•Ethical issues for larger organisms.

Question 16

What is gene therapy ?

Answer 16

•Replacing a faulty allele (e.g. that codes for a genetic disease) with a normal allele
•The two types are somatic and germ line.

Question 17

Differentiate between somatic gene therapy and germ line therapy

Answer 17

•Somatic - allele introduced to target cells only, short term, needs replacing
•Germ line - allele is introduced to embryonic cells so it is present in all resultant cells, permanent, passed onto offspring.