IB BIO TOPIC 4.4 : GENETIC ENGINEERING & BIOTECHNOLOGY Flashcards
Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA.
PART 1
• Makes millions of exact copies of DNA from a biological sample

• eg., Forensic application: DNA amplification with PCR allows DNA analysis on biological samples as small as a few skin cells. The ability of PCR to amplify such tiny quantities of DNA enables even highly degraded samples to be analysed. Great care, however, must be taken to prevent contamination with other biological materials during the identifying, collecting, and preserving of a sample.
State other examples for the use of polymerase chain reaction (PCR) : (medical & science)
eg., Medical application: DNA amplification with PCR allows DNA analysis on laboratory synthesised short pieces of DNA called probes, whose sequences are complementary to the mutated sequences. These probes are amplified and then will seek their complement among the three billion base pairs of an individual’s genome. If the mutated sequence is present in the patient’s genome, the probe will bind to it and flag the mutation.
• eg., Scientific application: DNA amplification with PCR allows DNA analysis on laboratory synthesised short pieces of DNA from the clone (called probes), whose sequences should be complementary to the parent or comparative clone sequences. These probes are amplified and then run through gel electrophoresis. The fragments of DNA will create banding patterns that can be compared to determine if the organism is in fact a clone.
In gel electrophoresis, fragments of DNA move in an electric field. How are they separated ?
According to their size.
When is gel electrophoresis of DNA used ?
Gel electrophoresis of DNA is used in DNA profiling.
Describe the application of DNA profiling in forensic investigations .
• Forensics: DNA fingerprinting for criminal cases
o collect samples of DNA-containing substance (blood, hair follicles, semen)
§ from suspect
§ from crime scene
o amplify quantity using PCR if necessary
o add endonucleases to produce DNA with Restriction Fragment Length Polymorphism
(RFLPs)*,
o use gel electrophoresis to separate RFLPs into DNA fingerprint o compare samples from crime scene and suspect for match
What is RFLP ?
RFLP is a technique for analysing the variable lengths of DNA fragments that result from digesting a DNA sample with a special kind of enzyme. This enzyme, a restriction endonuclease, cuts DNA at a specific sequence pattern know as a restriction endonuclease recognition site. The presence or absence of certain recognition sites in a DNA sample generates variable lengths of DNA fragments, which are separated using gel electrophoresis. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample.
How is DNA fingerprinting used to determine identity (paternity) ?
o collect samples of DNA-containing substance (blood, cheek cells, skin cells etc.)
§ from children
§ from suspected father/parent
o amplify quantity using PCR if necessary
o add endonucleases to produce DNA RFLPs
o use gel electrophoresis to separate RFLPs into DNA fingerprint
o compare samples from children and suspected father/parent for matching RFLP patterns
Summarise DNA profiling :
- sample of DNA obtained / leucocytes / hair / saliva / semen
- reference samples of DNA are obtained
- repetitive sequences used for profiling
- amplification of DNA by polymerase chain reaction (PCR) / produce more copies of the DNA
- cutting DNA into fragments using restriction enzymes
- separation of fragments of DNA (by gel electrophoresis)
- separation according to the length of the fragments
- pattern of bands obtained / different pattern of bands with DNA from different individuals
- bands compared between different samples
- if pattern of bands is the same then DNA is (almost certainly) from same source
- if some bands are similar then individuals are (almost certainly) related
For what is DNA profiling used :
Used:
• for criminal investigations / example of use in criminal investigation
• in archaeology / taxonomy
• to check paternity / who is the father / mother / parentage
• to check whether two organisms are clones
What are the Outcomes of DNA profiling:
- Knowledge of the number of human genes
- discovery of proteins and their functions
- evolutionary relationships between taxa
Outline 4 outcomes of the sequencing of the complete human genome.
- medical benefits:
• number of human genes = about 25,000
• huge improvements in sequencing technology
• new insights into the role of non-coding DNA
What are the medical benefits of the sequencing of complete human genomes ?
o diagnosis of disease, or predisposition to disease
o identification of disease carriers
o better drugs design using knowledge of protein structure eg. pharmocogenetics o greater success of gene therapy
What is the aim of the HGP ( Human Genome Project) ?
The aim of the Human Genome Project (HGP) was to determine the entire base sequence of every gene in the human genome. Also, to produce precise maps of the chromosomal location of each gene. The HGP was able to show/confirm:
• - the specific sequences of bases for a particular gene and its exact position on the chromosome eg., the insulin gene
• - the patterns such as where start and stop codons are located on genes
• - the variation in bases in different alleles and mutations
This has led to improved medical diagnosis, treatment and technologies/forensic analysis/phylogeny.
What happens when genes are transferred between species ?
the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.
Outline a basic technique used for gene transfer involving plasmids :
plasmids = vector = medium by which genes of interest are transferred to host o small (2 - 30 genes) loops of bacterial DNA which bacteria can:
§ capture from environment by transformation
§ replicate and transfer to other bacteria
