Chapter 2: Sources of DNA Evidence

 DNA is located in cells which are the building blocks of the human body  Two Types of cells:  Sex Cells  Somatic Cells Forensic Biology by Richard Li2

 Cell membrane  Cytoplasm  Nucleus Forensic Biology by Richard Li3

 Blood  Most common type found at crime scenes  Consists of erythrocytes (red blood cells), leucocytes (white blood cells), and platelets  Nuclear DNA obtained from leucocytes Forensic Biology by Richard Li4

 Hair  Consists of root and shaft  Medulla  Cortex  Cuticle  Grows at approximately 0.3mm per day  Anagen phase- growing phase  Catagen phase- follicle becomes inactive  Telogen phase- growth cycle ends Forensic Biology by Richard Li5

 Hair as a source of DNA evidence  PCR allowed more productive analysis of hair  Formerly just analyzed morphology and comparisons  mtDNA can be isolated from roots and shafts  Nuclear DNA analysis or hair is preferred ▪ Plucked hair with roots ▪ Naturally shed hairs contain little nuclear DNA ▪ Most hairs at crime scenes are naturally shed Forensic Biology by Richard Li6

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 Bone  Compact vs. Spongy  Osteocytes  Osteoblasts  Osteoclasts Forensic Biology by Richard Li8

 Bone  Rate of degradation of human remains varies greatly with environmental conditions  Soft tissue is lost  Bones are more stable  Mass Fatalities-identify victims  Sanding- used to reduce potential of comingled remains, adhering inhibitors, and bacterial contamination Forensic Biology by Richard Li9

 Teeth  Deciduous/Primary teeth vs. Secondary dentition/Permanent dentition  Dentin- Does not contain cells  Pulp Cavity  Root Forensic Biology by Richard Li10

 Teeth  Identity of a person ▪ Characteristics of teeth ▪ Alignment ▪ Overall structure ▪ X-rays  Bite mark analysis Forensic Biology by Richard Li11