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 Project2000- sequence of chromosomes 21 and 22

was completed.2001- publication of a draft of the 3 billion

base pairs (ATCG) of DNA in most human cells.

Completed in 2003. (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 MapA genetic map that shows the

relative locations (loci) of genes on a chromosome.

Gene linkage in humans is inefficientHumans 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 disordersGene therapyNew methods of crime detection

Genetic DisordersWe 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

presentCan also analyze DNA for diagnosis

using gel electrophoresis.

Gel Electrophoresis

Gene TherapyThe 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 FingerprintingUsed 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 Investigations1. 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

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