Download GENETIC SEROLOGY PP JANUARY 2016

SEROLOGY AND GENTICS
DR. GRAY
JANUARY 2016
GENETICS
• THE VEHICLES OF GENTIC INFORMATION
TRANSFER ARE GENES. Genes are found in
sequential combinations along each of the arms
of a chromosome. A chromosome is a collection
of genes (alles)
• During reproduction a sperm and egg combine to
form a zygote. The zygote is formed by the
contribution of 23 chromosomes from each of
the sperm and egg.
GENETICS
• An X chromosome is contributed to the zygote by
the egg.
• The sperm will contribute either an X or a Y
chromosome, resulting in the developing sex of
the embryo. XX for female and XY for a male.
• The sperm cell determines the chromosome pair,
and therefore determines the developing sex of
the embryo.
GENETICS
• Genes that govern oppisite characteristics of a
given trait (brown eyes v. green eyes) are found
on opposite arms (locus) of the chromosome.
Such a pair is known as an allele-or an allelic
trait.
• Gene pairs for a given trait may result in
expressing a dominant trait (homozygous) or a
recessive trait (heterozygous).
GENETICS
• The given expression of a gene pair will result
in a physical expression of the combined trait.
• This outward, or physical, expression of an
allelic pair is known as the phenotype.
• Genetisists may use a punnett square test to
trace the origins of a given trait or expression.
GENETICS
• There is a much less percent chance of a
recessive trait being expressed in a given
cross.
• So, if blood type AO is dominant over BO, AO
will be the phenotype that is expressed.
• PATERNITY TESTING
• Based on the blood genotypes of the offspring
and parents.
GENETICS
• Most of the results of paternity testing can be
resolved with the use of a punnett square.
• Routine paternity testing involves the
identification of blood factors other than those
involved in the ABO SYSTEM.
• The text mentions the HLA (human leukocyte
antigen ) system as an alternative method of ID
the parents of an offspring.
GENETICS
• THERE ARE SEVERAL IMPORTANT TESTS
WHICH MAY BE USED IN THE IDENTIFICATION
OF SEMEN FLUID. THESE ARE PARTICULARLY
IMPORTANT IN THE CASE OF MAKING AN ID IN
A CRIMINAL SEXUAL ASSUALT CASE.
• THERE IS NO RELIABLE MEANS OF
RECOGNIZING SEMEN STAINS OF FABRICTHERE IS NO CONSISTENT APPEARANCE.
GENETICS
• THERE ARE TWO IMPORTANT TESTING
MEHODS USED IN THE ID OF SEMEN STAINS.
THESE CONSIST OF BOTH THE ACID
PHOSPHATASE TEST AND THE PSA (PROSTATE
SPECIFIC ANTIGEN).
• ACID PHOSPHATASE HAS A HIGH
CONCENTRATION IN THE SEMEN-UP TO 400
TIME SGREATER THAN OTHER BODILY FLUIDS.
GENETICS
• THE USE OF AN ACIDIC SOLUTION OF SODIUM
ALPHA NAPPHTHYLPHOSPHATE AND FAST
BLUE B DYE, WILL FLOURESCE UNDER UV
LIGHT WHEN IT COMES IN CONTACT WITH
THE ACID PHOSPHATASE.
• PROSTATE SPECIFIC ANTIGEN:
• P30 IS VERY SPECIFIC TEST
GENETICS
• THE PSA TEST INVOLVES THE USE OF
POLYCLONAL ANTIBODIES WHICH MAY BE
DIRECTED AGAINST THE P30 PROTIEN (ANTIP30).
• THE ABOVE TEST IS SET UP IN A
ELECTROPHORESIS PROCESS.
GENETICS
• IN SUMMARY, THE ACID PHOSPHATASE TEST
IS THE BEST METHOD FOR POSITIVE
IDENTIFICATION OF SEMEN STAINS ON
FABRIC.
• A FORENSIC EXMINER WHO CAN DETECT THE
PRESENCE OF SPERMATOZOA OR P30 (PSA) IN
A BODY FLUID SAMPLE-HAS POSITIVELY ID
SEMEN FLUID