Ch. 19 Part 4

Do Now Review Primer Probe Short length of DNA that attaches to one end of a single strand of DNA Allows DNA polymerase to begin to make a complementary copy of a single template strand Probe Short length of DNA that attaches to one end of a single strand of DNA Labeled in some way (fluorescence or radiation; phosphorus) Emits beta radiation that can be detected Indicates position of DNA

Gene Technology Enables humans to make necessary products (commercial and medical) Production of valuable human proteins: Human Insulin E. coli used to produce this protein Bypasses ethical concerns and accessibility concerns of using animal insulin Human growth hormone Factor VIII Blooding clotting protein Inability to make this protein leads to hemophilia Enzyme ADA Adenosine deaminase Used to treat Severe Combined Immunodeficiency Disease (SCIDs) ADA vital for functioning of immune system

What Researchers Use to Make Proteins Bacteria Advantages: Simple nutritional requirements Large volume produced Low space of production facilities Process carried out anywhere Few practical or ethical problems collecting protein this way Disadvantages: Do not modify proteins in same way eukaryotic cells do Yeasts Cultures of mammalian cells BEST source Transgenic animals

Examples of Eukaryotic Cells Being Used To Make Protein GM Hamster Cells Used to make Factor VIII Kidney & ovary cells Gene for Factor VIII inserted into GM hamster cell Cells cultured in fermenter Cultured cells constantly produce factor VIII Protein is purified and treated before given to humans GM Insect Larva From Cabbage Looper Moth Caterpillar Used to produce ADA protein for SCIDs Given to patients awaiting gene therapy Transgenic Animals Genetically modified to produce human proteins in their products (milk) Sheep Goats

Transgenic Animals Sheep Goats Makes human alpha- antitrypsin Used to treat emphysema Goats Makes human Anti- thrombin protein Used to stop blood clotting Anti-thrombin deficiency leads to increased risk of venous and arterial thrombosis

Genetic Screening Analysis of a persons DNA to check for presence of a specific allele Done to: Adults Fetus Embryos In utero In vitro Screen for faulty genes Useful for disordered where there may be a hereditary disposition Results can be used to prevent onset of disorder or to prepare treatments for disorder

Designer Baby Muscular dystrophy Thalassaemia Hemophilia Pre-implantation genetic diagnosis (PGD) Utilizes Mixing sperm with oocytes in petri dish Removal of cell from embryo during 8-cell stage DNA analyzed and used to predict if embryo would have genetic disorder for which both parents were carriers for Embryo WITHOUT the disease causing alleles is chosen as the one to be used for implantation Embryos with the disease allele discarded (ethical concerns) Popular technique to avoid pregnancies with: Muscular dystrophy Thalassaemia Blood disease similar to sickle cell anemia Common in Mediterranean Decrease in disease due to genetic screening Caused by mutated allele Parents can be carriers If fetus has the disease, therapeutic abortion is an option (termination of pregnancy for medical reasons) Hemophilia Huntington's Disease Late onset disease Symptoms appear at middle age (after children have been born) No cure Dominant allele (but some times disease does not develop) Ethical dilemmas 2004 UK Used to produce child with tissue match to older sibling who had genetic disorder Stem cells from umbilical cord used in sick sibling Ethical Concerns Downs Syndrome Cystic Fibrosis Designer Baby

Ethics of Genetic Screening UK Law, 2004 Allowed embryo to be chosen that did NOT have disease allele to produce baby Allowed embryo to be chosen that was a tissue match for another child in the family that needed those cells Does NOT allow addition of an allele into egg, sperm, or zygote Decision to Terminate Pregnancies Where to draw the line? Minor chance vs. major Other features such as gender

Fetal Genetic Screening Tests Amniocentesis Sample of amniotic fluid taken at 15-16 weeks of pregnancy Analysis of sample can check for genetic disorders- mainly chromosomal mutations Ultrasound scanning used to view placement of fetus, placenta, and umbilical cord Hypodermic syringe needle position marked on skins surface Needle inserted and extracts amniotic fluid Chance of miscarriage Chorionic Villus Sampling Carried out between 10 to 13 weeks of pregnancy Early warning of genetic abnormalities in fetus (earlier than amniocentesis) Ultrasound scanning used to located fetus and placenta Hypodermic needle used to extract sample of fetal chronic villi fluid located in the placenta Sample of fetal blood Increase risk of miscarriage Before 15 weeks, less risky than amniocentesis

Genetic Counselor/counseling: Doctor who will help people interpret results of the genetic screening tests and help them make decisions Difficult Moral, ethical, scientific issues Right to terminate life?

Gene Therapy Process of inserting normal alleles of genes into people who suffered from genetic disorders Cystic fibrosis a hereditary disorder affecting the exocrine glands Causes the production of abnormally thick mucus, leading to the blockage of the pancreatic ducts, intestines, and bronchi and often resulting in respiratory infection Sickle Cell anemia Difficulties with gene therapy Getting normal alleles of genes into a persons cells Making these normal alleles function properly in new cells 1st successful Gene Therapy 1990, Ohio, 4-year old girl with SCID (severe combine immunodeficiency disorder) Isolated in bubble Inability to make ADA protein (adenosine deaminase) Patient’s T-lymphocytes removed & normal ADA alleles inserted into cells using virus vector Cure not permanent; regular transfusion needed to maintain immune system function Adult Stem cells from bone marrow used for gene therapy 2000, France  children getting transplant developed leukemia due to retrovirus used as vector

Vectors to Carry Normal Alleles into Patient’s Cells Viruses Retroviruses Insert their genes into host’s genome randomly May interfere with regulatory sequence of a gene in hosts’ cells  activate gene causing cancer Lentiviruses Insert genes randomly into host genome Can be modified to inactivate replication HIV disabled to act as vector AAV (adeno-associated virus) acts as vector Virus does NOT insert its genes into the host genome = not passed onto daughter cells Problem with short lived cells (lymphocytes) Successful with long-lived cells (neurons and liver cells) Liposomes Small spheres of phospholipids