Download 13.3- The Human Genome

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
2000- 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 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.
2.
3.
4.
Small sample of DNA is obtained from
suspect and blood, hair, skin or semen at
a crime scene.
DNA is cut into fragments with
restriction enzymes.
Fragments are separated by gel
electrophoresis and analyzed.
If samples match- the suspect is
probably guilty.
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13.3
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