Manipulating genomes

Question 1

What is DNA sequencing?

Answer 1

Identifying the base sequence of a DNA fragment

Question 2

Give benefits of genome wide comparisons

Answer 2

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

Question 3

What is DNA profiling?

Answer 3

Identifying the unique areas of a person’s DNA making a profile individual to them

Question 4

Give uses of DNA profiling

Answer 4

Forensics

Medicne

Question 5

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

Answer 5

Using polymerase chain reaction which makes millions of copies of a fragment which are cut at different lengths to be sequenced

Question 6

How is gel electrophoresis used in DNA profiling?

Answer 6

• DNA fragments of varying length in agarose gel
• Electric current applied
• Shorter fragments travel further, pattern of bands are unique to every individual

Question 7

How is a DNA fragment isolated?

Answer 7

Restriction enzymes cut DNA at specific sequences but can leave uneven strands, one with longer unpaired bases has sticky ends and is hard to insert

Isolation mRNA for the desired gene, uses reverse transcriptase to produce a single strand of comp DNA

Question 8

How is a DNA fragment inserted into a vector?

Answer 8

A plasmid is used as the vector and is cut using the same restriction enzymes as the DNA

Ligase joins them

Question 9

How is the vector inserted into a host cell?

Answer 9

Host cells are mixed with vectors in a cold solution then shocked to increase membrane permeability which encourages cells to take up the vectors

Question 10

Ethical issues around genetic engineering

Answer 10

+ Insect resistance can be introduced to crops
+ GE animals used to produce pharmaceuticals
+ GE pathogens can be produced for research
- GE seeds harder to acquire for poorer farmers

Question 11

What is gene therapy?

Answer 11

• Replacing a faulty allele with a normal one
• Somatic and germ line

Question 12

Differentiate between somatic gene therapy and germ line

Answer 12

Somatic= allele introduced to target cells only, short term and needs repeating

Germ line= allele introduced to embryonic cells so it is present in all resultant cells, permanent and will be passed to offspring

Question 13

Introns

Answer 13

Non coding

Question 14

DNA profiling

Answer 14

Producing an image of patterns in the DNA of an individual

Question 15

Producing a DNA profile

Answer 15

1. Extracting DNA
2. Digesting sample= DNA cut into fragments using restriction endonucleases, they cut at the restriction site
   - they make 2 cuts once through each DNA strand
3. Separation
   - Electrophoresis
   - Gel immersed in alkali to separate DNA double strands into single strands
   - Transferred onto a membrane by southern blotting
4. Hybridisation
   - Radioactive or fluorescent DNA probes are added
   - Bind to comp strands (hybridisation)
5. Seeing the evidence
   - UV tags glow, radioactive labels seen on x ray images

Question 16

Polymerase chain reaction

Answer 16

1. Temperature increased to 90-95c for 30 seconds to denature the DNA
2. Temperature is decreased to 55-60c and primers annea to ends of DNA strands
3. Temp increased to 72-75c which is the optimum temp for DNA polymerase to add bases to the primer
   - Produces identical DNA strands
   - Uses Taq polymerase which is a thermophile which can withstand extremely hot conditions

Question 17

What is computational biology and bioinformatics used for?

Answer 17

Bioinformatics= The dev of software and coputing tools needed to organise biological data

Computational biology= uses data from bioinformatics to build theoretical models of biological systems which can be used to predict what will happen in certain circumstances

Question 18

What does sequencing genomes of pathogens enable?

Answer 18

• doctors to find out the source of an infection
• Doctors can identify antibiotic resistant strains of bacteria
• Scientists can track the progress of an outbreak of a potentially serious disease
• Scientists to identify regions in the genome of pathogens that may be useful targets in the development of new drugs

Question 19

Identifying species

Answer 19

• Identifies particular sections of the genome that are common to all species but vary between them
• Allows comparisons to be made also known as DNA barcoding
• the region chosen is a 648 base pair section of the mitoDNA in the gene cytochrome c which codes for an enzyme used in respriation

Question 20

How can plant species be identified?

Answer 20

• DNA does not evolve quickly enough to show clear differences
• however 2 regions in the DNA of chloroplasts have been identified which can be used in identification

Question 21

Proteomics

Answer 21

The study and amino acid sequencing of an organism’s entire protein complement

• evidence highlights the complexity of the relationship between phenotype and genotype

Question 22

How can proteomics predict sequences?

Answer 22

• knowing the DNA sequences should mean that you can predict amino acid sequence