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 FABRIC- THERE 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 (ANTI- P30). 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