Chapter 21 - Manipulating Genomes

Question 1

What is DNA sequencing?

Answer 1

Identifying the base sequence of a DNA fragment.

Question 2

How have sequencing methods changed over time?

Answer 2

• Entire genomes can now be read (with the help of computers)
• Used to be a manual process, but is now automated

Question 3

Give some benefits of genome-wide comparisons.

Answer 3

• Comparing interspecies allows us to determine evolutionary relationships
• Comparing between individuals of the same species allows us to tailor medical treatment to the individual.

Question 4

How can DNA sequencing be used in synthetic biology?

Answer 4

Knowing the sequence of a gene allows us to predict the sequence of amino acids that will make up the polypeptide it produces. This allows for development of synthetic biology.

Question 5

What is DNA profiling?

Answer 5

Identifying the unique areas of a person’s DNA, in order to create a profile that is individual to them.

Question 6

Give uses of DNA profiling

Answer 6

• Forensics - DNA obtained during crime investigations can be compared to that of victims or suspects.
• Medicine - To screen 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

PCR - Polymerase Chain Reaction

- Makes millions of copies of a fragment, which are cut at different lengths in order to be sequenced.

Question 8

Describe the reaction mixture in the first stage of PCR

Answer 8

DNA fragments (to be amplified), complimentary primers, free nucleotides to match exposed bases, and DNA polymerase (create new DNA)

Question 9

Summarise the process of amplifying DNA fragments using PCR

Answer 9

1. Heat (95C) break apart DNA strands
2. Cool (50C) to allow primers to bind
3. Heat again (72C) to activate DNA polymerase and allow free nucleotides to join.
4. New DNA acts as template for the next cycle.

Question 10

How is Gel Electrophoresis used in DNA profiling?

Answer 10

• DNA fragments of varying length are placed at one end of a slab of gel
• Electric current is applied; DNA fragments move towards the other end of the gel
• Shorter fragments travel further. The pattern of bands created is unique 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 differing species) - done via use of a vector and a host cell.

Question 12

Summarise the process of isolating a DNA fagment.

Answer 12

• Restriction Enzymes (RE) cut DNA at specific sequences.
• Different REs cut at different points - however, one RE will always cut at the same sequence. Therefore, using particular REs alows you to cut out a certain gene of interest.

Question 13

Summarise the process of inserting a DNA fragment into a vector.

Answer 13

• A plasmid (circular DNA from bacteria) is used as the vector, and is cut using the same restriction enzymes as the DNA - therefore, ends are complimentary.
• DNA ligase joins fragment and plasmid together.

Question 14

Summarise the process of inserting a vector into a host cell

Answer 14

• The hose cells (bacteria) are mixed w/ the vectors in an ice-cold solution, then shocked to increase the permeability of the cell membrane (electroporation)
• Encourages the cells to take up the vectors.

Question 15

Give some ethical issues around genetic engineering

Answer 15

• GE animals used to produce pharmaceuticals (pharming)

- GE seeds would be hard to acquire for poorer farmers.

Question 16

What is Gene Therapy?

Answer 16

Replacing a faulty allele (e.g. one that codes for a genetic disease) with a normal allele.

Question 17

What are the two types of Gene Therapy?

Answer 17

Somatic - allele introduced to target cells only (short term)
Germ line - allele introduced to embryonic cells so it is present in all resultant cells. (permanent, will be passed to offspring.)