Biological Fluids: Blood, Semen, Saliva, and an Introduction to DNA

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Chapter 13

• Biological Fluids Blood, Semen, Saliva, and an
  Introduction to DNA

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Objectives

• Students should gain an understanding of
• Tests for the presence of blood
• Serological blood typing
• Tests for the presence of saliva
• Tests for the presence of semen
• The principles of paternity
• DNA, genes, and chromosomes
• Mitochondrial DNA

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Introduction

• Prior to the development of DNA typing, forensic
  serology was the primary technique of crime labs.
• Most labs still use basic serological testing
  procedures.
• Some do not have a DNA typing facility owing to
  either a lack of resources or a lack of enough
  cases to warrant the investment.

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Blood (1 of 2)

• Plasma the liquid portion of blood
• Accounts for 55 of the total blood volume
• Consists of 90 water and 10 dissolved materials

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Blood (2 of 2)

• Cellular components of blood
• Account for 45 of the total blood volume
• Include three major types
• Erythrocytes red blood cells
• Leucocytes white blood cells
• Thrombocytes platelets

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Tests for the Presence of Blood (1 of 6)

• Police want to answer three questions
• Is this blood?
• Is it from a human?
• How closely does it match the blood of the victim
  or the suspect?

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Tests for the Presence of Blood (2 of 6)

• Presumptive tests for blood
• Luminol sprayed directly on bloodstained object
  produces a glow when it contacts blood
• Color tests

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Tests for the Presence of Blood (3 of 6)

• Serological tests for blood precipitin
  serological test
• Determines if blood is of human origin
• Can be used with antiserum prepared for other
  animals if it is negative for human blood
• Requires only a small blood sample
• May produce a positive result even if bloodstains
  were washed down to a tiny sample remaining
• Is highly sensitive even when bloodstains are odd

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Tests for the Presence of Blood (4 of 6)

• Serological blood typing
• ABO system separates human blood into four broad
  classifications based on the presence or absence
  of the antigen A or antigen B on the surface of
  red blood cells
• Rh factor expressed as positive or negative

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Tests for the Presence of Blood (5 of 6)

• Because blood types are inherited from a persons
  parents, blood types may become concentrated
  among certain ethnic groups.
• 80 of the population are secretorsthey have
  significant concentrations of antigens in other
  body fluids.

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Tests for the Presence of Blood (6 of 6)

• Other blood typing systems based on the presence
  of proteins in red blood cells
• Polymorphic proteins occur in multiple forms.
• Different forms can be identified and their
  statistical occurrence in the population
  calculated.
• The more independent factors that can be
  identified in a blood sample, the smaller the
  percentage of the population possessing that
  combination of blood traits.

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Forensic Characterization of Saliva (1 of 2)

• Characteristics of saliva
• Consists of more than 99 water
• pH range 6.87.0
• Contains salivary amylase (a digestive enzyme)
• Produced in three main pairs of salivary glands
  parotid, submaxillary, sublingual
• Cleanses mouth and provides lubrication

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Forensic Characterization of Saliva (2 of 2)

• Saliva is always present at the crime scene if
  there are bit marks on the victim.
• It can be used to identify an individual through
  DNA profiling.

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Forensic Characterization of Semen (1 of 2)

• Characteristics of semen
• Consists of more than 90 water
• pH range 7.27.4
• A crime scene may include a large number of items
  stained by semen (e.g., garments, bed clothing,
  rugs, drapes, solid surfaces).

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Forensic Characterization of Semen (2 of 2)

• Identification of semen
• At the crime scene UV light
• Presumptive tests acid phosphatase test, p30
  test
• In the laboratory direct observation of sperm
  under a microscope

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Rape Evidence Collection (1 of 4)

• Conviction often hinges on the ability to link
  the perpetrator to the victim and the victims
  injuries.
• Gather evidence from both the physical
  surroundings and the victim
• Collect the victims clothing if the victim is
  still at the scene
• Ensure that the victim is examined by a physician
  immediately

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Rape Evidence Collection (2 of 4)

• Physical evidence collected from the victim
• Blood sample Head hair
• Combings from pubic hair Fingernail scrapings
• Pubic hair reference samples Oral swab
• Vaginal swab and smear All clothing
• Rectal swab and smear Urine specimen

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Rape Evidence Collection (3 of 4)

• Saliva residues
• Collect saliva from the victims skin if the
  assailant bit, sucked, or licked an area of the
  victims body

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Rape Evidence Collection (4 of 4)

• Physical evidence collected from the suspect
• All clothing
• Combings of pubic hair
• Head hair and pubic hair standards
• Penile swab
• Blood sample

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Principles of Paternity (1 of 4)

• Nucleus largest structure in a human cell
  controls heredity
• Ribosomes site of protein synthesis
• Mitochrondria site of energy production

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Principles of Paternity (2 of 4)

• Chromosomes hereditary material found in the
  nucleus
• Egg cell contains an X chromosome
• Sperm contains either an X or a Y chromosome
  determines the sex of the offspring

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Principles of Paternity (3 of 4)

• Chromosomes are made of nucleic acids.
• Deoxyribonucleic acid (DNA) is the primary
  hereditary material.
• DNA consists of a series of coding regions and
  noncoding regions that are arranged along the
  chromosomes.
• Genes are sections of the DNA molecule.
• Pairs of chromosomes are considered homologous
  because they are the same size and contain the
  same information.

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Principles of Paternity (4 of 4)

• When fertilization occurs, one chromosome is
  inherited from the mother and one is inherited
  from the father.
• Sons inherit their Y chromosome from their
  father, so paternity can often be determined by
  comparison of the Y chromosomes from father and
  son.

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Introduction to DNA (1 of 13)

• Functions of nucleic acids
• DNA and RNA are responsible for storage and
  transmission of genetic information.
• They determine how genetic information is
  transferred from one cell to another and how
  genetic traits are transferred from parents to
  offspring.
• The major function of DNA is control and
  direction or protein synthesis in body cells.

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Introduction to DNA (2 of 13)

• Nucleic acids are composed of long chains of
  repeating units (nucleotides).
• Each unit includes three components
• Sugar
• Nitrogen-containing heterocyclic base
• Phosphoric acid unit

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Introduction to DNA (3 of 13)

• A nucleic acid can contain any of five bases
• Adenine double-ring base (a purine)
• Guanine double-ring base (a purine)
• Cytosine single-ring base (a pyrimidine)
• Thymine single-ring base (a pyrimidine)
• Uracil single-ring base (a pyrimidine)

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Introduction to DNA (4 of 13)

• Structure of nucleic acids
• Adenine, guanine, and cytosine found in both DNA
  and RNA
• Thymine found in DNA
• Uracil found in RNA

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Introduction to DNA (5 of 13)

• Primary structure of a nucleic acid sequence of
  the four bases
• Secondary structure the double helix

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Introduction to DNA (6 of 13)

• The double helix each DNA molecule has two
  polynucleotide chains wound around each other
  like a spiral staircase
• The phosphatesugar backbone represents the
  handrails
• Pairs of bases linked together by hydrogen bonds
  represent the steps
• Hydrogen bonds hold the two chains together under
  normal physiological conditions

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Introduction to DNA (7 of 13)

• DNA
• Carries the information needed for making and
  maintaining the different parts of an organism
• Chromosomes
• Consist of DNA in the nuclei of cells coiled
  around proteins (histone molecules)
• Humans have 46 chromosomes, 23 from each parent
• Genes
• Are segments of DNA molecules that control the
  production of different proteins in an organism
• Vary in terms of the number and sequence of base
  pairs they contain

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Introduction to DNA (8 of 13)

• Cell replication
• Before a cell divides, the double helix strand
  begins to unwind.
• Each unwinding strand serves as a template for
  the formation of a new complementary strand.
• Nucleotides are attracted to the exposed bases
  and become hydrogen-bonded to them A to T, T to
  A, C to G, G to C.

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Introduction to DNA (9 of 13)

• Ribonucleic acid (RNA)
• Primary structure is similar to DNA
• Ribosephosphoric acid units form backbone
• Each ribose unit is bonded to one of the four
  bases
• Protein synthesis a series of complex steps
  involving RNA
• Transcription
• Translation

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Introduction to DNA (10 of 13)

• Protein synthesis transcription
• A single strand of RNA is synthesized inside the
  cell nucleus.
• A segment of the DNA double helix separates into
  single strands.
• The exposed bases of one strand act as the
  template for the synthesis of an RNA molecule.
• The base sequence (messenger RNA) complements the
  base sequence on the DNA strand with one
  exception RNA transcribes a uracil instead of a
  thymine to adenine.

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Introduction to DNA (11 of 13)

• Protein synthesis translation
• The code that has been copied to the new protein
  is interpreted.
• mRNA leaves the nucleus and takes its chemical
  message to the cytoplasm of the cell, where it
  binds with ribosomes.
• Guided by the first codon on the mRNA strand, a
  transfer RNA molecule with an anticodon that is
  complementary to this codon transports a specific
  amino acid to the mRNA codon

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Introduction to DNA (12 of 13)

• Protein synthesis
• The actual protein synthesis occurs in the
  ribosomes, which move along the mRNA one codon at
  a time as the amino acid chain grows.
• The mRNA is read codon by codon and the protein
  is built up one amino acid at a time in the
  correct sequence.

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Introduction to DNA (13 of 13)

• The genetic code
• Each three-base sequence in mRNA codes for a
  specific amino acid
• 64 three-base codons can be formed from the four
  bases in mRNA

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Nuclear DNA and the Law (1 of 2)

• 1985 routine analysis of the structure of human
  genes led to the discovery that portions of the
  DNA structure are as unique to each individual as
  fingerprints
• 1987 individuals were first convicted of rape
  based on DNA evidence (in both the United States
  and the United Kingdom)

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Nuclear DNA and the Law (2 of 2)

• State v. Woodall the court accepted the results
  of DNA testing, but ruled that the inconclusive
  results failed to exculpate Woodall
• Spencer v. Commonwealth admission of DNA
  evidence led to guilty verdicts resulting in the
  death penalty for the defendant
• People v. Castro the court required laboratories
  and personnel to follow appropriate practices and
  prove the validity of their procedures before DNA
  evidence would be accepted in court
• DNA testing is generally accepted as admissible
  under Frye or Daubert standards

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Mitochondrial DNA

• Mitochondria
• Provide 90 of the bodys energy
• Contain DNA that can be used for testing purposes
• Mitochondrial DNA (mtDNA)
• Is circular and much smaller than nuclear DNA
• Is inherited from the mother
• State of Tennessee v. Ware (1996) first use of
  mtDNA in court to match hair samples at the crime
  scene to the suspect