Biological Evidence
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What are mitochondria ?
Cellular organelles responsible for energy production through oxidative phosphorylation
Where are mitochondria located ?
Cytoplasm
How many genes do mitochondria have ?
37
what is the inheritance pattern of mitochondrial DNA ?
MtDNA is inherited exclusively from the mother. All maternal relatives share the same mtDNA sequence
When was mtDNA fully sequenced ?
1981
What are the advantages of using mitochondrial DNA ?
-high copy number: each cell contains hundreds of thousands of mitochondria -maternal linage tracing: allows for identification of maternal relatives across generations -databases can be created
What are the limitations of using mitochondrial DNA ?
-lack of individuality: mtDNA is shared among all maternal relatives across -Heteroplasmy: the presence of multiple mtDNA types within an individual, which can complicate interpretation
Where is the most mitochondria most likely to be found ?
The more energy the tissue requires the more mitochondria
What are mitochondria critical for ?
Cellular metabolism and function
What is Sanger sequencing ?
-uses single-stranded DNA template, primer, DNA polymerase, ddNTPs and fluorescent labels -ddNTPs terminate DNA extension and emit specific wavelengths of light -sequence determined by electrophoretic separation
What is the Y chromosome ?
One of the two sex chromosomes in males
What is the Y chromosome characterised by ?
• approximately 60 million base pairs -contains 200 genes -passes exclusively from father to son -highly stable
What is the inheritance pattern of the Y chromosome ?
Inherited only through male lineage, sons receive Y-chromosome from their fathers
What are the advantages of using Y chromosomes ?
-tracing paternal lineages -male-specific, allowing for isolation of male DNA in mixed samples
What are the limitations of using Y chromosomes ?
-lack of individuality: shared among male relatives -limited genetic diversity compared to autosomal markers
What is the difference in lineage markers ?
Autosomal- passed on in part from all ancestors Y-chromosome- passed on complete but only by sons Mitochondrial- passed on complete but only by daughters
What is LMD (laser micro-dissection)
-isolates sperm cells from microscope slides -allowing re-analysis -effectively separates sperm from mixed cell types without loss of male material
What is LCN an extension of ?
SGM plus (10 autosomal loci + sex marker)
What are the different techniques used in LCN ?
-increased PCR cycles -enhanced detection methods
What are the PCR cycles increased to in LCN ?
From 28-30 to 34-35
What are limitations of LCN ?
-require careful handling to avoid contamination -increased risk of contamination can lead to false positives -incorrect or misleading results can complicate interpretation
What are common biological fluids in forensics ?
-blood -saliva -semen -vaginal secretions -urine
What are the identification methods for biological fluids ?
-immunological tests/ chemical tests -molecular methods -RNA-Based methods
What are spectroscopic techniques of bodily fluid analysis ?
-Raman Spectroscopy: Analyses light scattering to create complex spectra for fluid identification; variability observed with aging bloodstains. -Fourier Transform Infrared (FT-IR) Spectroscopy: Evaluates biological fluids while accounting for environmental contamination.