Piecing Together an Identity

1. Piecing Together an Identity

2. Blood Group Antigens • Antigens are defined as substances recognized by the body, causing the body to produce an antibody to react specifically with it. • Antibodies are proteins that react specifically with an antigen • When a blood antigen and antibody react with each other agglutination occurs

3. Blood Typing vs Secretor Status If the saliva of a secretor is mixed with the antiserum or lectin specific for its blood group substance then most of the antibody in the antiserum will bind to the blood group substance in the saliva. So when you add the red blood cells for that type no clumping or very little clumping should be observed. This is the opposite of what you would see during a traditional blood test.

4. Importance of Gender • Establishing individual identity is an imperative aspect of any investigative procedure. Determination of gender helps in investigations by narrowing down potential pools of victims of potential pools of suspects.

5. X Chromosome Inactivation X Chromosome Inactivation • Since cells in a male contain a single X chromosome and cells in a female contain two X chromosomes, females contain twice as many copies of the genes on the X chromosome per cell as do males. To equalize the dosage of X chromosome genes between the two sexes, one of the two X chromosomes in each cell of all female mammals is inactivated early in embryonic development by becoming very tightly wound up or condensed. These condensed chromosomes are Barr Bodies.

6. Barr Bodies Barr bodies allow one to distinguish between male and female mammals but will not be able to tell if the cell containing the Barr body is human.

7. Secretor Status • The term “secretor” refers to the presence of A, B, and H substances in the body fluids, such as in sweat, tears, saliva, and serum. • Secretor status is used when blood or blood products are too degraded or not available.

8. Amelogenin • The amelogenin gene for tooth pulp is six bases shorter on the X chromosome than on the Y chromosome. When amplified and examined on an agarose gel, a female will have one band, (two X’s) and a male will have two bands one for the X and one for the Y. • So the use of this gene is a common identifier to determine gender.

9. Mitochondrial DNA • With nuclear DNA, a child receives half of its DNA from each parent in any give strand, half of the sequence will match the mother’s DNA and the other half will match the father’s DNA. • In the case of mitochondrial DNA, an exact copy is inherited from your mother as it has been passed from all of the female relatives on your mother’s side of the family.

10. Heteroplasmy • A very small portion of the mitochondrial DNA might be a contribution from the male parent. • This occurs only if the tail of the sperm enters the egg during the process of fertilization. • The head of the sperm is an empty vessel that contains the DNA of the male parent. • The tail of the sperm must contain mitochondria to supply energy for the process of locomotion.