DNA, or deoxyribonucleic acid, is a molecule that contains the human genetic code. It is similar to a recipe book that holds instructions for making every protein in our bodies.
The human genome is made of DNA and is a complete set of genetic building blocks. It contains all of the information needed to make a human and allow it to grow and develop. It has about 3.2 billion base pairs and is packaged into 23 pairs of chromosomes.
Chromosomes are molecules that contain hereditary information for everything from body type to eye color. They are made of DNA, and contain our genetic code, passed down from generations. Chromosomes are arranged in pairs within the nuclei of our cells.
Humans and most mammals have an additional pair of chromosomes. The extra pair determines gender and are referred to as X and Y. Their combination is different in women and men. Females have two X chromosomes while males possess one X and one Y.
In the past 20 years, DNA testing has become commonplace. Tests can be performed using blood, saliva, semen or even minute skin samples left behind on touched surfaces.
Portions of DNA are unique to each individual. DNA profiling is a way of establishing identity or heritage and can be used in many ways, such as finding out whether twins are fraternal or identical or establishing parent/child relationship.
DNA technology is increasingly utilized in our criminal justice system. It can identify perpetrators with incredible accuracy (one in a million) when there is biological evidence.
DNA profiling is used to solve crimes in several ways. In cases where a suspect is identified, a sample of that person’s DNA can be compared to evidence from the crime scene. That evidence can be on a glass or a cigarette butt or in bodily fluid. Results of the comparison can help establish whether or not the suspect committed the crime.
In cases where there is not a suspect, evidence from the crime scene can be analyzed and compared to profiles in DNA databases to help identify a perpetrator. Crime scene evidence can also be linked to other crimes through the use of DNA databases.
Every state has a provision for the establishment of a DNA database that allows the collection of DNA profiles from persons convicted of certain crimes. CODIS (Combined DNA Index System” is a computer program that allows law enforcement agencies to compare DNA profiles electronically. This can link serial crimes and identify suspects by matching profiles from crime scene evidence with DNA samples taken from convicted offenders and arrestees.
Contrary to public opinion, DNA profiling isn’t infallible. Critics point out various problems and limitations, including: DNA profiling technologies can give false positives or incorrect results, due to errors caused by poor collection practices or cross-contamination of samples; DNA profiles can only offer statistical probability, rather than absolute certainty; the more people tested, the lower the statistical probability there is for an exact match; the probability of one in a million may fall to one in 10,000 if enough people are profiled; DNA databases are vulnerable to exploitation via hackers or data loss and evidence can easily be planted at a crime scene.
Some legal scholars argue that holding a person’s DNA profile on record is, in a sense, a violation of that person’s DNA “ownership.”
DNA can also be used to clear suspects and persons mistakenly accused or convicted of crimes. For example, the Innocence Project has gotten many convictions reversed in the United States. The first DNA case reversal took place in 1989, and since 2000, there have been 263 exonerations. Twenty of those people served time on death row and another 16 were charged with capital crimes but not sentenced to death.
Opponents of the death penalty have used these statistics to argue that innocent people can be (and probably have been) put to death. So far, the Supreme Court has ruled execution constitutional.
There are many other uses of DNA testing. The one that offers great promise in the future is in the field of predictive medicine. Diagnostic DNA can identify whether an individual will likely get a certain genetic disease. This type of test commonly detects a specific gene alteration or mutation. Results are usually expressed in terms of probability and can be influenced by other genetic and nongenetic factors such as environment and lifestyle. This testing can identify individuals with increased risk of developing certain forms of breast and colorectal cancer.
The Human Genome Project, using multiple computers, mapped and sequenced the approximately 100,000 genes of human DNA. The focus of the project was the advancement of genetic knowledge that could be used to combat disease, effect human physiology, develop new medicines and much more.
Marcus Goodkind of Tuckasegee, a retired aerospace engineer, worked with the National Aeronautics and Space Administration as a manager at Kennedy Space Center on all the manned programs from Mercury to Shuttle, including Apollo 11, the first manned lunar landing.