Human Genome Project - International Baccalaureate Biology - Lecture Slides, Slides of Biology

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Human genome project

• Purpose
• 1. Determine the nucleotide sequence of the human genome
• i. e., a normal person
• 2. Determination of the function and location of genes.

Information used

• 1. Linked genes.
• 2. Restriction fragment analysis.
• 3. Comparison of human sequences to

those of other organisms where the function of the genes are known.

• 4. Sequencing.

Problems / Challenges

• 1. Distinguishing normal variation from variation causing abnormalities.
• 2. Specific genetic disorders may be caused by many different mutations.
• Example: hemophilia can be caused by any 1 of 208 variations in DNA

• 3. Genetic abnormalities may be the result of the interaction of genes.
• 4. Most abnormalities are not solely due to genes.
• 5. In many cases it is unclear how genetic disorders are to be treated.

2. Restrict exposure to chemicals

which the missing gene product

reacts with.

• Example : treatment of PKU with low phenylalanine diet.

3. Gene therapy

• Definition:
• Treatment of a disease by modifying a patients genes.

Extract cells from patient with abnormal allele

Place normal gene in retrovirus

Infect cells

Normal gene becomes part of cells chromosomes

Inject modified cells back into patient

• 3. Germ cell therapy:
• treatment of cells that do produce gametes.

2 types of non coding DNA

• 1. Promoter and terminator sequences.
• 2. Repetitive sequences. Copies of the same DNA sequences found in various locations in the genome.
• Probably the result of retroviruses and transposable elements.

Transposable elements

(transposons)

• Discovered by Barbara McClintock in the 1940’s.
• Sections of DNA that can move from one region to another in the genome.

• If a transposon inserts into a gene, it makes the gene non functional
• Transposon enzyme cuts sections of DNA with specific sequences and pastes the section into another region in the genome

Variability in the human genome

• Non coding region
• Highly variable
  • because
• mutations generally have no effect on the organism.

Coding region

• About 6% of genes have more than one allele.
• Variation within groups of humans is generally as great as variation between groups.