13.3- The Human Genome

What is a genome? Genome: the total number of genes in an individual. Human Genome- approx. 20,000 genes on the 46 human chromosomes. Human Genome Project (HGP) ◦ Ongoing effort to completely map and sequence our genome.

Human Genome Project sequence of chromosomes 21 and 22 was completed publication of a draft of the 3 billion base pairs (ATCG) of DNA in most human cells. Completed in (13 year project) “The results of the Human Genome Project included a better understanding of the roles genes play in the human body. Scientists learned that there were fewer genes than originally believed that make up the human genome. They were able to learn that all genes do not have one specific role, as was previously believed, but can actually make up to three proteins” (Discovery Channel).

Linkage Map A genetic map that shows the relative locations (loci) of genes on a chromosome.

Gene linkage in humans is inefficient Humans only produce a few offspring. Human generation time is long (lifetime). Alternative Method: ◦ PCR (amplifies DNA fragments in hours) ◦ Fragments can contain genetic markers that can be traced throughout the genome. ◦ Used to track the inheritance pattern of a gene that hasn’t been identified but whose approximate location is known.

Applications of the Human Genome Project Improved techniques for prenatal diagnosis of human disorders. Diagnosis of genetic disorders Gene therapy New methods of crime detection

Genetic Disorders We want to find where the gene is located and that a mutation of the gene is the cause of the disorder. Can diagnose disorders before birth by taking cells from fluid that surrounds fetus and amplifying the cell’s DNA using PCR. ◦ If deviations are found  a mutation is present Can also analyze DNA for diagnosis using gel electrophoresis.

Gel Electrophoresis

Gene Therapy The insertion of normal genes into human cells to correct genetic disorders. ◦ Used to treat disorder SCID (severe combined immunodeficiency syndrome).  Cells of immune system are removed from bone marrow and the functional gene is added to them.  Modified cells are then injected back into the patient. ◦ Trials involving gene therapy: hemophilia, some cancers, AIDS, heart disease, cystic fibrosis.

DNA Fingerprinting Used by law enforcement to determine if suspects have been at a crime scene. DNA patterns can be used like fingerprints to identify the person from whom they came. This process works because no two individuals have the same DNA sequences.

Forensic Investigations 1. Small sample of DNA is obtained from suspect and blood, hair, skin or semen at a crime scene. 2. DNA is cut into fragments with restriction enzymes. 3. Fragments are separated by gel electrophoresis and analyzed. 4. If samples match- the suspect is probably guilty.

PLEASE COMPLETE THE PROBLEM SOLVING LAB: 13.3 (Page 353)