Human Genome Project and Genetic Fingerprinting Analysis
The Human Genome Project
The human body consists of approximately 10 trillion cells. Each cell contains 46 chromosomes (23 pairs), and each chromosome holds a specific number of genes. The Human Genome Project is a national scientific research initiative focused on determining the sequence of chemical base pairs that constitute human DNA and identifying all genes within the human genome.
Launched in 1990 by a U.S. government agency, this project was technically and scientifically challenging, involving the development of cutting-edge technologies. Its success signaled the commercial and scientific superiority of the country. In 1996, the project evolved into a public consortium. This phase focused on highly accurate sequencing: chromosomes were separated, cut into pieces, and the sequence of bases for each one was individually identified. Concurrently, Celera Genomics was founded; they fragmented all human chromosomes simultaneously and used a computer program to reorganize the complete genome.
Genetic Fingerprinting
An individual's DNA is a long sequence of 3 billion base pairs. While 99.9% of the genome sequence is identical in all humans, scientists focus on the 0.1% that differs. In 1985, a method was discovered to obtain a genetic fingerprint. This method identifies specific regions of DNA where small fragments are repeated; the number of times these fragments repeat varies between individuals.
- Paternity tests: These involve comparing the genetic fingerprints of the child, the mother, and prospective fathers. The child possesses a series of bands corresponding to the mother, while the remaining bands must match the father.
- Criminal investigations: Forensic experts compare the genetic fingerprint of a sample found at a crime scene with the DNA fingerprints of suspects.
Characteristics of the Human Genome
The human genome contains approximately 3.2 billion base pairs. Only 2% of the genome contains genes that provide information to produce proteins. A very high percentage consists of "junk DNA," the exact function of which is still being studied. The genome is almost identical for all people, with only 0.1% accounting for individual differences. It contains about 25,000 genes—a number similar to that of a chimpanzee or a mouse—and the function of nearly half of these genes remains unknown.
Prenatal Diagnosis
Prenatal diagnosis is used to determine if a child will be born healthy. Chromosome analysis is typically indicated if the mother is over 35 years old, if there is a family history of anomalies, if healthy parents carry a known abnormality, or if anomalies are detected during pregnancy.
Types of Diagnostic Tests
- Chorionic villus biopsy: This involves the extraction and study of chorionic villus cells where the tissues of the mother and fetus meet. It is performed at 11–12 weeks of pregnancy. The risk of miscarriage is 1.1%, and the procedure is performed via the vagina.
- Amniocentesis: A needle is inserted through the abdominal wall into the uterine cavity to collect amniotic fluid. The risk of miscarriage is less than 0.5%, and results typically take 3 to 4 weeks.