Applying Our Knowledge of Genetics

Selective Breeding Selective breeding (domestication) has been going on for centuries. It is simply the process by which people choose the animals or plants with the best traits and breed them together to get offspring that have all of those same traits. Animal breeders and farmers do this all the time. The organisms with the best traits are used to make the next generation and since most traits are based on your DNA…You are picking the best DNA to make up the offspring. Positive – You know what you are going to get in your offspring. Only desired traits show through. Negative – You end up with a “monoculture” and homogeneity…All are the same…Not so good if something comes along that can kill one of you…It can kill all of you!

Genetic Screening & Counseling Genetic screening is a process used by those in the medical field to see if someone has a defective or lethal gene in their genetic code. This may lead to someone seeing a genetic counselor. Genetic counseling occurs when an expert in the field of genetics and medicine explains one or more of the following to a patient that has a genetic disorder. Items discussed may include: –Cause of Disorder –Symptoms and/or Treatments –Odds of Passing it on to Children –Clinics and/or Facilities Where Help is Available

Prenatal Diagnosis There are a variety of prenatal tests that are performed on babies while they are still in the womb. A prenatal diagnosis involves testing a fetus to check for possible health-related risks. Possible testing procedures include: –Amniocentesis – A portion of the amniotic fluid is removed and analyzed. Amniotic fluid surrounds the fetus while in the womb and contains fetal cells. –Ultrasound – using sound waves to “see” the fetus. –Chronic Villus Sampling – Cells surround the fetus are removed and analyzed. This is only done in high risk cases because there are risks associated with it. –Maternal Serum Screening – Mother’s blood is taken and analyzed for abnormal protein levels that cross from child to mom. (DNA  RNA  Protein)

Recombinant DNA In a recombinant DNA experiment, scientists attempt to take DNA from one organism and implant it into the DNA of a second organism. We have had success in taking human genes, like the one for insulin, and inserting them into bacterial cells. The bacterial cells adopt the gene and make insulin according to the directions on the human DNA – it is human insulin! We use restriction enzymes that cut DNA at specific sequences (A’s, C’s, G’s, & T’s) and remove the gene from the human cell’s DNA. It is then put into a bacterial cell plasmid (DNA) that is cut open using the same restriction enzyme. Some of the plasmids will adopt the gene and when the bacterial take in the plasmid – they make the proteins that the plasmid DNA makes – including our insulin!

Recombinant DNA Recombinant DNA can be used to make transgenic plants and animals (maybe people someday) that have healthy genes inserted into them to replace or mask the effects of faulty genes. A transgenic plant may have the toughness genes of a desert plant inserted into a fruit- bearing plant in order to help feed those in harsh environments such as those in some third world countries.

Gene Therapy Gene therapy involves the insertion of a properly working gene into a patient that has a faulty gene in hopes that the new, healthy gene could be used to cure the disorder. A vector, or DNA delivery system, would need to be used to insert the “foreign” DNA into the patient’s cells. Some vectors being used are viruses and plasmids. Stem cells are usually the target cells because they have not matured yet and will divide and differentiate after the DNA has been inserted into them. There are some problems… –Hard to deliver to all cells. –Immune response of patient to vector. –Cells do not always divide after they receive the foreign DNA.

Gene Therapy

Human Genome Project The human genome project began in 1990 and its goal was to map out the “genetic library”. It would mark the position of genes on the chromosomes and then go back and sequence those genes according to DNA nucleotide sequence – the A’s, C’s, G’s and T’s. The scientists will now know the position and code associated with each gene in the human genome. It is hoped that this information will be used to make stronger connections between phenotypes and genotypes. (DNA Codes  Observable Traits)

Cloning…Cloning…Cloning… Scientists studying reproductive technology are now using nuclear cloning to create living organisms that are exact copies (clones) of previously living organisms. Basically, here is what we do… –Scientists take body cell from creature to be cloned and an unfertilized egg cell from another individual. –They remove the DNA from the egg and place the DNA from the body cell into it. –The egg now has 46 chromosomes and will be implanted into a surrogate mother. –The egg/zygote matures and is given birth to…It looks exactly like the donor DNA and not the mother! No…Humans are not going to give birth to dogs, horses or sharks…That is crazy talk!

Cloning…Cloning…Cloning…

That’s All I Got…