6. True or False: The advent of DNA technology has dramatically altered the approach forensic scientists have taken toward the individualization of bloodstains and other biological evidence.
7. True or False: The fundamental principle of blood typing is that for every antigen, there exists
a specific antibody.
8. True or False: The standard test sued to determine whether a blood stain is of human or
animal origin is the precipitin test.
9. True or False: Today it is possible for forensic scientists to successfully link seminal material to
one individual with DNA technology.
10. True or False: The presence or absence of four antigens determines an individual’s blood type
in the A-B-O system.
11. What technique supplanted blood typing for associating bloodstain evidence with a particular
Characterizing biological evidence by elect regions of DNA supplanted blood typing for
associating bloodstain evidence with a particular individual. 12. What is plasma? What percentage of blood content does plasma account for?
Plasma is the fluid portion of the blood. It accounts for 55 percent of blood content. 13. Which of the following types of cells are not contained in plasma?
14. What are antigens and antibodies? What part of the blood contain antibodies?
An antigen is a substance that stimulates the body to produce antibodies against it. An
antibody is a protein in the blood serum that destroys or inactivates a specific antigen.
Antibodies are contained in the blood serum. 15. Describe how antibodies and antigens determine one’s A-B-O blood type?
type O). The type of antigen on ones red blood cells determines one’s A-B-O blood type.
People with type A blood have A antigens on their red blood cells, those with type B blood
have B antigens, and those with type O blood have no antigens on their red blood cells. 16. What is the fourth important antigen other than A, B, and O?
Rh factor (D antigen) is the fourth important antigen other than A, B, and O. 17. What happens when serum containing B antibodies is added to red blood cells carrying the B
antigen? Will the same thing happen if serum containing B antibodies is added to red blood
cells carrying the A antigen? Explain your answer.
When serum containing B antibodies is added to red blood cells carrying the B antigen, the
blood agglutinates, or clots. This does not happen when serum containing B antibodies is
added to red blood cells carrying the A antigen because an antibody reacts only with its
specific antigen and no other. 18. Briefly describe how antibodies capable of reacting with drugs are produced in animals.
To produce antibodies capable of reacting with drugs, the analyst first combines a specific
drug with a protein and injects this combination into an animal such as a rabbit. This drug-protein complex acts as an antigen, stimulating the animal to produce antibodies. The recovered blood serum of the animal now contains antibodies that are specific or nearly specific to the drug. 19. What is the greatest problems associated with detecting marijuana in urine?
The greatest problem associated with detecting marijuana in urine is that it is difficult to determine when the individual actually used marijuana. 20. What is the difference between monoclonal and polyclonal antibodies?
Monoclonal antibodies are designed to attack one and only one site on an antigen. Polyclonal antibodies attack a variety of different sites on an antigen. 21. Name the most common color test for blood and briefly describe how it identifies bloodstains.
The most common color test for bloodstains is the Kastle-Meyer test. This test is based on the fact that enzymes called peroxidases accelerate the oxidation of hemoglobin in the blood. When a bloodstain is subjected to this test, oxidation of the hemoglobin in the blood produces a deep pink color. 22. Briefly describe how luminol is used to detect bloodstains.
To detect bloodstains, luminal reagent is sprayed onto suspect items and the room containing the items is darkened. Any bloodstains produce a faint blue glow, known a luminescence. 23. What is the standard test used to determine whether blood is of human or animal origin?
Briefly state the principle underlying the test.
The standard test used to determine whether blood is of human or animal origin is the precipitin test. This test is based on the fact that when animals (usually rabbits) are injected with human blood, antibodies are formed that react with the invading human blood to neutralize its presence. 24. Which technique takes advantage of the fact that antibodies and antigens move toward one
another on a plate coated with medium made from a natural polymer called agar?
Gle diffusion takes advantage of the fact that antbodies and antigens move toward one another on a plate coated with a medium made from a natural polymer called agar. 25. In what technique can antigens and antibodies be induced to move toward one another under
the influence of an electrical field?
In electrophoresis, antigens and antibodies can be induced to move toward one another under the influence of an electrical field. 26. Define gene and chromosome.
The gene is the basic unit of heredity. A chromosome is a threadlike structure in the cell nucleus along which the genes are located.
the cell? What cells are the exception to this rule? How are these cells different from all other cells?
Most human cells contain forty-six chromosomes, arranged in twenty-three mated pairs. The only exceptions are the human reproductive cells, the egg and sperm, which contain twenty-three unmated chromosomes. 28. Describe how genetic material is transferred from parents to offspring.
During fertilization, a sperm and egg combine so that each contributes twenty-three chromosomes to form the new cell, or zygote, that develops into the offspring. The chromosomes from a parent carry that parent’s genes, so the new individual begins life with twenty-three mated chromosomes pairs, each carrying genetic material from one of the parents. In this way, the new individual inherits genetic material from each parent. 29. What is an allele?
An allele is any of several alternative forms of genes that influence a given characteristic and that are aligned with one another on a chromosome pair. 30. What is the difference between a heterozygous gene pair and a homozygous gene pair?
A heterozygous gene pair is made up of two different alleles; homozygous gene pair is made up of two similar alleles. 31. What is the difference between a dominant and a recessive gene?
Two different genes are inherited, the characteristic coded for by dominant gene is expressed. The characteristic coded for by a recessive gene remains hidden. 32. Define genotype and phenotype. What is the only way to determine an individual’s genotype?
A genotype is the particular combination of genes present in the cells of an individual. A phenotype is the physical manifestation of a genetic trait such as shape, color, or blood type. An individual’s genotype can be determined only by studying his or her family history. 33. The best way to locate and characterize a seminal stain is to perform what test? In what
situation is this test particularly useful?
The best way to locate and characterize a seminal stain is to perform the acid phosphatase test. The acid phosphates test is particularly useful when it is necessary to search many garments or large fabric areas for seminal stains. 34. Define oligospermia and aspermia.
Oligospermia is an abnormally low sperm count. Aspermia is the absence of sperm, or sterility in males. 35. The presence of what protein proves that a sample stain contains semen? What two
techniques are used to detect this protein?
The presence of prostate specific antigen (PSA), or p30, proves that a sample stain contains semen. Two techniques used to detect this protein are electrophoresis and monoclonal antibody testing.
Besides swabs, blood and urine samples should be collected from a rape victim during a medical examination. 37. What terms should be collected from the suspected perpetrator of a sexual assault?
The following items should be collected from the suspected perpetrator of a sexual assault: all clothing, and any other items believed to have been worn at the time of the assault, pubic hair combings, pulled or cut head and pubic hair standard/reference samples, a penile swab (when appropriate to the case history), and a blood sample or buccal swab for DNA typing.