Chapter 13Gene Technology

Facts about Human DNA

• Except for identical twins, no one has the same DNA

• 10% of genome is different (person to person)– Use these differences to compare/ID– Restriction length polymorphisms (RLPM)

• (Variable number tandem repeat)

DNA fingerprinting

• Able to compare DNA samples in regions of a chromosome that differs

• Use in – paternity– identification of human remains– tracing human origins– evidence in criminal cases

Steps in Identification

1. Copy DNA (Polymerase Chain Reaction)

2. Cutting DNA (Restriction Enzymes)

3. Sorting DNA by size (Electrophoresis)

Polymerase Chain Reaction (PCR)

Don’t have enough of a sample-need to make copies

Cutting DNA: Restriction Enzymes

EcoR1: Bacterial protein

Sort DNA: Gel Electrophoresis

1. Cut DNA is placed in wells of thick gel

2. Electric current runs through gel

3. Negatively charged DNA migrate to + end

4. Smaller fragments go faster and farther

GENE THERAPY• Use of nucleic acids as medicine

• Introduction of a gene into a patient’s cell

• 5,000+ people worldwide are already treated with Gene Therapy

How does it work?

1. Isolate the functional gene

2. Insert the healthy gene into a viral vector

3. Introduce the recombinant virus to the patient (infect the patient)

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Cystic Fibrosis

• Lung disease

• Lack of functional gene (CFTR gene)– Encodes for a protein that helps transport ions

into and out of cells in breathing passage– Without the gene: poor ion exchange causes the

buildup of sticky mucus that blocks the airway

Cystic Fibrosis cont.

• 1989, discovered the CFTR gene

• Have had some trials of adding healthy copies into cells– No cure yet– Cells that line the airway slough off

periodically– Treatments must be repeated

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Severe Combined Immunodeficiency

• Bubble Boy– 1976 David Vetter

• Loss of a cytokine receptor (one gene is missing)– Can’t make B and T

cells

• X-linked

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SCID cont..

• Take bone marrow from patient

• Use a virus to carry a new version of the gene into immune cells from the marrow

• Reimplant into the patient

• Began to generate further cells

• Study done: 9/10 were completely restored

Cloning

• Introduction of a nucleus from a body cell into an egg cell to generate an organism identical to the nucleus donor

• Dolly(1996)– Suffered premature aging and disease– Had short telomeres-premature aging– Died at age 6– Other cloned species, have not had telomere shortening– http://images.google.com/imgres?imgurl=http://wwwimage.cbsnews.com/images/2004/09/08/image642074x.jpg&imgrefurl=http://

www.cbsnews.com/stories/2004/09/08/eveningnews/main641999.shtml&usg=__3XK03j8Ov6p2Nh2zP2HJh70LFtI=&h=278&w=370&sz=15&hl=en&start=12&um=1&tbnid=ReSiW4_1Z6oO4M:&tbnh=92&tbnw=122&prev=/images%3Fq%3Dclone%2Byour%2Bpet%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN

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Vaccines• Made by using one or more genes from a

pathogen• Does not have disease-causing capability• Immune system mounts a defense against

the protein• If come in contact again…ready to defend

STEM CELL

• Embryonic stem cells– Can reproduce indefinitely in culture– Have the potential to grow into any cell type– Harvested from human embryos that are unused

for fertility treatment– Embryo is destroyed

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• At blastocyst stage: all cells are precursors to placenta, some to embryo

• No exclusively embryonic cell population until 14 days.

HeLa cells

• Cells taken from Henrietta Lacks• Died from cancer on Oct. 4, 1951• Cells taken from her cervical

cancer mass• Immortal line of cells• Have been used for cancer research• The total number of cells that have

been propagated in cell culture far exceeds the number of cells in her body

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• Adult Stem Cells– Found in colon, brain, bone marrow

– Naturally produce just one or a few types of cells

– Limited life span in the lab

– Avoid possible immune response

• Already used for– Bone marrow

– Grafts for cancer

– Sometimes genetic blood disese

– Cultivated skin grafts for burns*

– Limbus grafts for cornea*

– *a few cases

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Induced pluripotent stem cells (iPs)

• Reprogram adult human cells to a pluripotent state (act like embryonic stem cells)

• Introducing genes for 4 important stem cell transcription factors-into adult human fibroblasts using engineered retrovirus– OCT4, SOX2, NANOG, LIN28

• Easy to make• No embryo• Made from the individual patient

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