DNA & Genetics Flashcards
What are the applications of DNA profiling?
- forensic cases: matching suspect DNA with evidence
- paternity testing: identifying father
- mass disasters: identifying body parts
- missing persons investigations
- DNA databases: cold case investigations
DNA typing much be performed …… and ……..
Efficiently and reproducibly (evidence must hold up in court)
What is the basis of DNA profiling?
The genome of an individual is unique (apart from twins) and is inherited from parents
What is a genotype?
Genetic constitution of an individual, the total complement of inherited traits or genes of an organism
What is an allele?
Alternate form of a gene at a specific locus
What is phenotype?
Trait determined by genotype and environment
What is a heterozygote?
Different allele
What is a homozygote?
Same allele
How much do humans differ by at a DNA level?
0.1 - 0.2% (3-6million base pairs)
How many base pairs are in the human genome?
3.4 billion
What are the forms of variation?
- Sequence polymorphism (single nucleotide polymorphism)
- Lengths polymorphism (indel)
- Copy number variation
- Chromosome inversions/genome variation
When was the first use of DNA profiling?
- 1984: Sir Alec Jeffreys
- lead to the conviction of Colin Pitchforker for the rape and murder of two girls in 1988 and the release of another suspect
What are the disadvantages of Southern blot?
- long process
- requires lots of high quality DNA
Southern Blot process
- restriction enzyme added to DNA
- electrophoresis to separate DNA in Aragone gel
- transfer DNA from gel to membrane
- probe membrane with labelled DNA of interest
What does PCR do?
Increases amount of target DNA
Mitochondrial DNA
- > 1000 copies/cell
- maternally inherited
- not unique to individual (ie siblings with same mother)
- target regions in forensics: highly variable region 1 (HV1) and HV2
What variation is used in DNA profiling?
Short tandem repeats (STRs)
Why are STRs used?
- high level of variability wishing most populations
- have multiple alleles
What is the PCR process?
- denaturing: 95o: hydrogen bonds between DNA strands break and the double helix is separated
- annealing: 56o: primer binds to target DNA sequences
- extending: 72o: Taq polymerase adds complementary nucleotides to the existing single stranded DNA
Repeated for 25-30 cycles
What is microbial forensics used for?
To trace outbreaks or micro-organisms (personal, bioterrorism or contamination)
What does microbial forensics include?
- using DNA and non DNA methods
- detection of molecular variation between microbial strains
- can infer the origin, relationships, or transmission route of a particular isolate/strain
What are the different transmission routes?
- aerosol (via droplets)
- oral (via consumption/inhalation)
- direct contact
- vector Bourne (via insect)
- zoonotic (via another animal)
What is anthrax?
Disease caused by Bacillus anthracis spores
Why are spores used in bio crime?
- highly resistant
- can be made into an aerosol using common ingredients (silica)
- odourless and invisible
- potential to travel many kilometres
How does transmission in personal bio crime occur?
- Microbes transfer between humans
- Microbes have a genome
- Their genomes changes over time
- Genomes can be compared just like human DNA
- It’s not that simple though as mutation rate is so high
How do phylogenetic trees work?
Points closer to each other are more genetically similar
Category A diseases
- anthrax
- botulism
- plague
- smallpox
- tularaemia
- Ebola
Category B diseases
- meliodosis
- glanders
Category C diseases
- influenza
- SARS
Category A biological agents
- highest priority
- easily disseminated from person to person
- high mortality rates
- cause public panic and social disruption
Category B biological agents
- second highest priority
- moderately easy to disseminate
- moderate morbidity and low mortality
Category C biological agents
- thirds highest priority
- have the potential for mass dissemination in the future
- have potential for high morbidity and mortality
