Emerging Trends - Phenotyping
- Created by: AAntonianannetti
- Created on: 14-05-19 10:16
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- Emerging Trends
- DNA profiling developments
- 1985 - Sir Alec Jeffreys published the first paper detailing DNA fingerprinting and how it could be used for identification purposes in biological samples
- DNA is powerful identification tool than blood groupings and had a high discriminatory power
- Initial method used by Jeffrey was difficult to perform in the lab and varying results were not obtained
- Required a certain amount of DNA which meant it was not appropriate for many biological samples
- Especially forensic samples which are often degraded
- The sensitivity of the technique needed to be improved and by the end of the 1980s, DNA profiling had replaced DNA fingerprint, and the method of PCR had been developed.
- Meaning that biological samples with smaller amounts of DNA could be analysed
- Important for forensic science applications
- Meaning that biological samples with smaller amounts of DNA could be analysed
- Required a certain amount of DNA which meant it was not appropriate for many biological samples
- Initial method used by Jeffrey was difficult to perform in the lab and varying results were not obtained
- DNA is powerful identification tool than blood groupings and had a high discriminatory power
- Continued research into genetic mapping
- Resulted in more polymorphisms being identified,, particular shorter repeat units of 2-6bp (STRs)
- Several STRs could be combined into one analysis and fluorescent dyes allowed the fragments to be detected
- Resulted in more polymorphisms being identified,, particular shorter repeat units of 2-6bp (STRs)
- Ability to store DNA profiles digitally
- Allows easier comparison
- Developments of Y-STRs and mtDNA profiling techniques
- Familial, Paternity, missing persons and mass identification
- Current techniques (DNA 17) are highly sensitive and discriminating
- Can be used on degraded and difficult samples
- 1985 - Sir Alec Jeffreys published the first paper detailing DNA fingerprinting and how it could be used for identification purposes in biological samples
- Determining behavioural traits
- Chromosome regions have been identified which might be linked to smoking, left handedness and stuttering
- Not as easy to identify
- Chromosome regions have been identified which might be linked to smoking, left handedness and stuttering
- Determining physical appearance
- Phenotype
- Coding regions of DNA
- Insertion/deletions of bases or SNPs within a coding region can alter the proteins made and in some cases a phenotypic change can be observed
- Phenotyping
- Still in its infancy
- Requires identification of SNPs within a gene or non-coding region that shows association with a particular trait
- Lack of detailed understanding of the basis of natural human variation
- Research funding tends to focus on disease-causing vairation
- Lack of detailed understanding of the basis of natural human variation
- Requires identification of SNPs within a gene or non-coding region that shows association with a particular trait
- Complex traits
- Determined by several genes, each with a small effect
- Requires large genome-wide association studies to achieve statistical significance
- Determined by several genes, each with a small effect
- Large environmental component
- A lot of the variation cannot be captured in genetic tests and can make prediction less accurate
- Ethical issues
- High potential for mismatches
- Stigmatisation
- Privacy
- Stigmatisation
- One off observation (by the witness) vs. the storage of genetic information on a persons EVC for future use
- Data becomes useable for different purposes
- High potential for mismatches
- Charactersitics
- Hair Colour
- Melanin and melanosomes
- HIrisPlex system for hair and eye colour - validation
- Only relevant in populations where there is variability in hair colouration
- HIrisPlex system for hair and eye colour - validation
- Melanin and melanosomes
- Eye Colour
- Most accurately predicted EVC
- Human traits with most variability in colour
- Defined by the amount of melanin and the number of melanosomes present
- Affects pigmentation
- Relies on finding an association between certain SNPs and particular eye colouration
- Affects pigmentation
- Defined by the amount of melanin and the number of melanosomes present
- Human traits with most variability in colour
- Most accurately predicted EVC
- Height and Age
- Very low predictive value as almost 700 genes involved in determining height
- Accumulation of mtDNA deletions and telomere shrinking
- Very low predictive value as almost 700 genes involved in determining height
- Skin
- Most complex pigmentation phenotypes
- Variability in skin colour is likely to have evolved as a response to UV intensities around the world
- Incomplete understanding of the genetics of skin pigmentation
- Variability in skin colour is likely to have evolved as a response to UV intensities around the world
- Most complex pigmentation phenotypes
- Hair Colour
- Still in its infancy
- Coding regions of DNA
- Predicting externally visible characteristics can provide important information
- Research began in 1990s
- Investigative Value
- At present, forensic DNA Phenotyping can only provide broad categorisations
- cannot be used for identification purposes
- value in generating investigative leads
- Limited however due to possibility of traits being altered
- value in generating investigative leads
- cannot be used for identification purposes
- At present, forensic DNA Phenotyping can only provide broad categorisations
- Phenotype
- DNA profiling developments
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