Applications of Genetics

1. Applications of Genetics SBI3U Mr. Tabone

2. Manipulating Genes • Even before Mendel humans have been using selective breeding to manipulate plant and animal populations • Domesticating dogs, increasing milk or wool production from livestock, using seeds from a hardy crop

3. Selective Breeding • Benefits • Desirable traits can be kept and undesirable trait can be eliminated from future generations • Drawbacks • Low genetic variety • Susceptibility to disease • High chance for expression of harmful recessive alleles (eg. albinism)

4. Hybridization • When 2 different species are bred together to create a new species • The new species is sometimes fertile and sometimes sterile • Eg: Loganberries are fertile hybrids of blackberries and raspberries • Eg: Seedless watermelons are sterile hybrids • Done to create crops resistant to weather conditions or disease, or to have desirable characteristics (no seeds)

5. Cloning • Cloning is a term that refers to creating an exact copy of an organism from one single cell • This is exactly what happens in mitosis • The biotechnology technique is slightly different from normal mitosis however • Multicellular organisms have two classes of cells • Stem cells and Specialized cells • Specialized cells have specific functions and are quite different from one another (muscle vs. brain vs. skin etc.) • Stem cells can divide and create any type of specialized cell

6. Cloning • Since specialized cells do not normally divide to create different specialized cells • Muscle cells only divide into muscle cells, they do not create brain cells (for example) • Adults are mostly composed of specialized cells, with very few stem cells • Therefore creating a clone animal out of a specialized cell is difficult • Traditionally stem cells have been used for the purpose of cloning

7. Cloning • Recently there have been many breakthroughs in this area, and some specialized cells can now be turned into clone cells and used for cloning • This is still a very active area of research • Dolly the sheep • Many species of animals have been successfully cloned • All have had short life spans and exhibited many physiological problems, like arthritis, premature aging, and lung disease • Click and Clone

8. Applications of Cloning • We can genetically modify certain organisms to give them advantageous traits and then clone them to produce several identical organisms • Eg: Producing corn plants that can grow in cold weather, or cows that produce more milk than normal • Cloning allows us to produce several organisms with our specific modifications • We already do this for several of our fruits and vegetables • Homework pg 151 #1-9, 11, 12

9. Gene Therapy • Using genes to treat disease • Used in two different ways • A normal gene product can be given to affected individuals • Manipulate genes in parents or offspring to treat the disease

10. Gene Therapy • Using gene products to treat disease • Leptin and obesity • Obese mice lack the receptor for the protein leptin • Leptin controls appetite • Leptin injections can help control obesity

11. Gene Manipulation • Involves replacing defective genes with properly functioning ones • Eg: replacing the non-functional gene that codes for leptin receptors in obese mice with a properly functioning one • Will often use specially-tailored viruses to deliver genes • Difficult to get copies of the desired gene into enough cells in the target tissues

12. Gene Manipulation • Problems with immune response to the viruses • Problems with division in the new cell line • Some success has been seen with adenosine deaminase deficiency (ADA) • Defect in a key protein involved in the immune response • Bone marrow stem cells are removed, manipulated, and replaced

13. Mutation • How are different alleles created? • One way is by mutations • Mutations are changes in the DNA sequence • Since DNA codes from protein synthesis, changing the DNA can alter the proteins made or stop them from being made all together • This can be both useful and detrimental

14. Mutations • Mutations can be caused several different ways, including; • Substitution • One base pair change • Deletion • Removing a section of DNA • Insertion • Inserting a section of DNA

15. Mutagens • Anything that alters DNA is labelled as a mutagen • Radiation and several chemicals can act as mutagens • Mutations in somatic cells often go unnoticed • Mutations in gamete cells are passed on • Cancer can be caused by mutation

16. Sickle Cell Anemia • A blood disorder caused by a recessive mutation on an autosomal chromosome • Blood cells are shaped like crescents instead of their normal shape • Sickle cells are not efficient at carrying oxygen • Being heterozygous for sickle cell anaemia confers resistance to malaria

17. Genetic Screening • Geneticists can identify if a person has an increased risk of inheriting a disorder • Genes can give an increased susceptibility to certain diseases • Huntington Disease • Autosomal dominant • Onset after 30-40 years of age • Diminished mental capacity and uncoordinated muscle movements

18. Genetic Screening • Cystic fibrosis • Large amount of mucus lining the lungs and digestive tract • Autosomal recessive trait • Would you want to know if you were susceptible to a certain disease? • Or if your kids would be susceptible?

19. Genetic Counselling • Counsellors determine whether an individual is at risk of inheriting detrimental traits • Such as sickle cell anemia, or a predisposition for cancer • It is possible that in the future we can know all the susceptibilities and predispositions an individual will have • What implications does this have for society?

20. Prenatal Diagnosis • Testing a fetus for problems before birth • Process is called amniocentesis • Extracting amniotic fluid (which contains some cells) with a syringe • Guided by ultrasound • Allows parents to be prepared for any special needs before birth