ABO Blood Type Inheritance

10 Questions

What is the primary step in determining the species origin of a blood sample?

Determining whether it is human or non-human blood

How is the sex of a person determined from a biological sample?

DNA typing

What type of samples are typically analyzed in a DNA analysis case?

Victim's blood, suspect's blood, and one or two questioned samples

What is the purpose of a differential extraction technique in seminal stains?

To separate sperm cells from vaginal secretions

Who typically conducts the analyses of biological evidence?

Any of the above

What is used to identify seminal stains?

Prostatic acid phosphatase test

Which of the following body fluids cannot be typed?

Urine

What is the primary purpose of identifying seminal stains in forensic analysis?

To match the DNA profile of the unknown sample with the DNA profile of the standard blood sample

Which of the following can be identified by the presence of amylase?

Saliva

Why are private laboratories used in forensic analysis?

For cases requiring paternity determination

Study Notes

ABO Blood Group System

ABO blood group system has three alleles: A, B, and O
A and B alleles are dominant over O
Individuals with AO genotype have A phenotype
Individuals with OO genotype have O phenotype
Individuals with AB genotype have AB phenotype due to codominance of A and B alleles
Agglutination tests can identify A and B characteristics in AB blood type

Presumptive Blood Tests

Used to identify blood at crime scenes
Based on color change or chemiluminescence of reagents when in contact with haemoglobin
Luminol is commonly used, but can react with other substances like bleach, saliva, and animal/vegetable proteins

Body Fluids

Liquids originating from inside the human body
Include fluids secreted or excreted from the body
Examples: bile, blood serum, breast milk, gastric juice, mucus, saliva, sebum, semen, sweat, tears, vomit, urine

Types of Bodily Fluids

Secreted: produced by cells, glands, or organs
Excreted: waste produced by the body, eliminated through processes like fecal matter, urine, tears, carbon dioxide, vomit, and sweat

Bodily Fluids as Evidence

Found on or about the body of a crime victim
Common bodily fluids found: blood, semen, and saliva
DNA analysis can identify individuals based on genetic factors
DNA typing has high power of discrimination and can be used for identification and characterization

Blood

Red fluid that circulates in veins and arteries
Functions: transport system, defense against infection
No substitute for blood; cannot be made or manufactured
Rhesus (Rh) blood type: Rh positive (83% in Australia) or Rh negative (17% in Australia)

Blood Group Compatibility

Plasma contains Anti-A and Anti-B antibodies depending on blood group
Patients should only receive plasma that does not contain an antibody that could attack their own red cells

Plasma Compatibility

Group O people have both Anti-A and Anti-B; group O plasma can only be given to group O patients
Group A plasma contains anti-B; can only be given to patients who are group A or O
Group B plasma contains anti-A; can only be given to patients who are group B or O

Detecting Semen

Ultraviolet light causes semen to fluoresce
Acid phosphatase test is used to detect semen, but can also react positively with other bodily fluids
Prostate-Specific Antigen (PSA) is used to detect semen, but can also be found in urine
Microscopic detection of sperm is a more confirmatory method

Blood Evidence Value

Valuable in crimes like murder, rape, assault, robbery, and burglary
Can aid investigation by locating crime scene, identifying weapon, proving or disproving alibi, and eliminating suspects
DNA profiling can be performed on any biological substance

Information Determined

Analysis must determine if a stain is blood, and then determine species origin
If human, further classification is achieved by isoenzyme and DNA analysis
Sex of the person can be determined by DNA typing
Private laboratories are used for DNA analysis in paternity cases