Molecular Pathology - Human and human remains identification Flashcards
List some reasons for identifying human remains
- Forensic matching
- Paternity testing
- Mass disasters
- Missing persons investigation
- Military identification
List all the genetic material in a cell
Nucleus: 23 pairs of chromosomes (Autosomes) + sex chromosomes
Mitochondria: Mitochondrial DNA mtDNA
List types of biological evidence
Blood Semen Saliva Hair Tissue, bone and teeth (human remains) Skin cells (Latent DNA, from touch)
Describe the function of STR typing
STR = short tandem repeats of 1-4bp sequences localized in specific regions of specific chromosomes
unique STR markers are used to match individual to database
e.g. US uses 15 unique STR markers to match DNA evidence to individuals
3 possible outcomes of DNA comparison
Exclusion
Inconclusive (e.g. sample contamination, low confidence…etc)
Probable match expressed as Random Match Probability
How is DNA match quantified?
Random Match Probability
Population data used to obtain various allele frequencies for calculation of RMP
Multiply individual allele frequency of each type to each STR marker
Effect of Random Match Probability on the strength of DNA match
Higher RMP = lower strength of DNA match
e.g. 1/100 = 1 in 100 share the same particular DNA profile
1/9,000,000 = 1 in 9 million share the same DNA profile
Name of DNA databank for criminals
Purpose of databank?
CODIS
- Combined DNA Index System
- Allow direct comparison of sample to all criminals
- Used to link serial crimes and repeated offenders
Criteria for giving DNA for Database in HK?
Serious criminal offense sentenced to imprisonment for more than 7 years
Precautions with DNA samples?
- Prevent contamination, mishandling
- Prevent degradation in storage
2 DNA types used for paternity and maternity testing
Paternity - Y-STR
Maternity - mtDNA
