Lecture 12: Biotechnology & Forensic

These flashcards cover key concepts in biotechnology and forensic science related to lineage markers, Y-STRs, and mtDNA, as discussed in the lecture.

What are lineage markers in forensic science?

Genetic markers inherited unchanged across generations, allowing the tracing of paternal or maternal ancestry.

What are the two main types of lineage markers?

Y-STRs (Y-short tandem repeats) for paternal lineage and mtDNA (mitochondrial DNA) for maternal lineage.

What is the forensic advantage of Y-STRs?

Y-STRs can be used for male-specific profiling, especially useful in female-biased mixtures.

What is mtDNA and when is it most effectively used in forensics?

Maternally inherited DNA found in mitochondria, effective when nuclear DNA is degraded or absent.

What is a haplotype?

A linked block of Y-STRs and mtDNA that acts as a single genetic locus.

What is the main limitation of Y-STR analysis?

Limited discrimination among direct paternal relatives as they share identical Y-STR profiles.

What is the mutation rate for Y-STRs compared to mtDNA?

Y-STRs have a higher mutation rate (≈10−3) than mtDNA (≈10−8), allowing for finer resolution.

Describe the Male-Specific Region (MSY) of the Y-chromosome.

Approximately 95% of the Y-chromosome, inherited as a single block from father to son, barring mutation.

What are the advantages of commercial Y-STR kits?

They offer more loci which enhance the discrimination power of the haplotype, making it more unique within a population.

What is the significance of the Revised Cambridge Reference Sequence (rCRS) in mtDNA analysis?

It serves as the forensic gold standard for comparison in mtDNA analysis.

What is homopolymeric C-stretch in mtDNA and why is it a challenge?

A repeated run of cytosines that can vary in length due to heteroplasmy, causing sequencing difficulties.

What are single nucleotide polymorphisms (SNPs)?

Variations at a single DNA base at a specific position, commonly used in forensic mtDNA analysis.

What are the categories of interpretation for mtDNA analysis according to SWGDAM Guidelines?

Exclusion (≥ 2 nt differences), inconclusive (1 nt difference), and cannot exclude (identical sequences).

What is the importance of population databases in mtDNA analysis?

They provide allele frequency data to estimate how common a haplotype is within different populations.

How is mtDNA utilized in genetic genealogy?

To trace maternal ancestry due to uniparental inheritance.

What challenges does heteroplasmy present in mtDNA interpretation?

Variability of mtDNA variants across tissues or samples complicates the interpretation of results.

How does the circular structure of mtDNA benefit forensic analysis?

It is more resistant to degradation compared to linear nuclear DNA.