DNA Typing Systems Flashcards
1
Q
What are the strengths of DNA testing?
A
- Discriminatory potential
- Great sensitivity
- DNA is stable in comparison to proteins
2
Q
What are the advantages of short tandem repeats?
A
- Can be used w/ degraded samples
- Small amount of DNA
- Number of loci is large
- Multiplexing and automation
3
Q
What are the limitations of short tandem repeats?
A
- Possibility of contamination is increased
- Equipment expensive
- Micro-variants (differ by less than one repeat)
4
Q
What is the difference between VNTR (minisatellite) & STR (microsatellite)?
A
- VNTR → short nucleotide sequence unit
STR → highly repetitive DNa - VNTRs are larger than STRs
- VNTR → repeating unit consists of 10-100 nucleotides
STR → repeating unit consists of 2-13 nucleotides
5
Q
What are single nucleotide polymorphisms?
A
Alterations at a single nucleotide position
Occurs once every 300 nucleotide base pair
6
Q
What are the advantages of SNP?
A
- Very numerous in mammalian genomes
- Single base changes → very short amplicons can be employed
- Whole genome SNPs microarrays → powerful for biogeographic identification
7
Q
What are the limitations of SNP?
A
- Bi-allelic → 3/4 alleles
- Less informative than multi-allelic STRs → complicates analysis of mixed samples
- Whole-genome SNPs microarrays → substantial amount of DNA
8
Q
What are some limitations of systems w/ sex-specific transmission used for human identification?
A
- High mutation rate
- Heteroplasmy
→ more than one mtDNA genotype occurs in one individual
→ levels of heteroplasmy may not always be the same in various tissues
→ 1 mtDNA type in 1 tissue & different type in different tissue - Lack of recombination
9
Q
What is the advantages of using mtDNA?
A
- Small amounts of DNA can be informative
- Not degraded as fast as nuclear DNA
- Useful marker for tracing family lineages
- Discriminatory power is larger than a single nuclear locus
10
Q
What are the limitations of using mtDNA?
A
- Cannot distinguish among maternal relatives
- Heteroplasmy can complicate the analysis
- MITOMAP → discrimation power limited by the database size
11
Q
When are Y chromosome markers useful in the forensic field?
A
- Excluding males in crime cases
- Kindship testing
- Disaster victims investigations
12
Q
What is the NGS HLA typign workflow?
A
- Sample prep
- HLA PCR
- Library construction
- NGS Seq
- Raw data
- Bioinformatics Analysis
- High resolution HLA results
13
Q
What are the benefits of NGS vs. Sanger Sequencing?
A
- Higher sensitivity to detect low-frequency variants
- Faster turnaround time for high sample volumes
- Comprehensive genomic coverage
- Higher throughput with sample multiplexing
- Ability to sequence hundred to thousands of genes or gene regions simultaneously
