1.2 Genes: Answers and Questions

1. 1.2 Genes: Answers and Questions

2. The Nucleus: control centre of the cell • The nucleus contains the master set of instructions that determines: • what each cell will become • how it will function • how long it will live before being replaced • These instructions are carried in chromosomes Chromosome – a thread-like structure made mostly of DNA, found in the nucleus of a cell

3. Chromosomes • Every species has a specific number of chromosomes • Chromosomes come in pairs (one from each of the parent) • Humans have 46 chromosomes (23 from the mother’s egg and 23 from the father’s sperm)

4. The DNA Code • Each chromosome consists of a single molecule of DNA DNA (deoxyribonucleic acid)– material found in the cell nucleus that contains genetic information [Dee-OXy RYE-bo-NEW-clee-ik] • DNA is divided into segments called genes Gene – a segment of DNA that controls protein production

5. Why is DNA important? • DNA controls many of your features (hair, eye colour) • Lifestyle choices also play a role in how your body functions and looks

6. Genes Direct Protein Production

7. The DNA Code • In 1953 scientists James Watson and Francis Crick created a model of DNA (the twisted ladder design is sometimes called a “double helix”).

8. DNA Screening DNA Screening – testing for the presence of genetic disorders

9. DNA Screening karyotype - micrograph of the chromosomes in a person’s cells • individual chromosomes from the karyotype can be mapped and then be examined for any irregularities Karyotype

10. Down Syndrome • can be detected in a fetus through amniocentesis • technicians look at chromosome 21 • positive test = 3 chromosomes (instead of the usual pair) • the extra chromosome leads to overproduction of certain proteins which result in physical and development disabilities

11. PKU • babies are tested after birth by examining a blood sample • if uncorrected, it can lead to severe brain damage • treatment includes following a diet low in natural protein • testing is inexpensive compared to the costs of treating PKU if not detected early

12. Huntington Disease • affects nerve cells • symptoms include loss of muscular control & brain function • normally appear in a person’s 40’s and worsen for about 15 years before the disease causes death • individuals have a 50% chance of having the gene if one of the parents have it • someone who has the gene will develop the disease Control HD

13. Issues Related to DNA Screening • DNA testing can reveal genetic disorders (such as Down Syndrome, PKU, Huntington Disease) and can help determine how susceptible a person might be to ailments such as cancers and heart disease. • The controversy related to genetic testing revolves around a variety of social issues.

14. Ethics of Genetic Screening AGAINST TESTING • may lead to needless emotional pain (if there is no cure, nothing can be done) • the testing is expensive (will not save lives) IN FAVOUR OF TESTING • results (positive or negative) reduce the stress of uncertainty • might change a person’s life decisions

15. Ethics of Drug Research Example: • Drug company develops an effective drug in lab condition • Carries out clinical trials on humans (very risky and expensive) • Tries to recover the cost by putting high price on drug • Ex. the annual cost of taking Kuvan (PKU drug) may be as high as US $200,000 • What do you think?

16. Ethics of Drug Research A company discovered a very expensive cure for cancer. • Does the company own the cure and has the right to sell it? • Does the company have an ethical obligation to make life-saving cures available to everyone?

17. Section1.2 Review Concepts to be reviewed: • genetic material in the nucleus: DNA, chromosomes, and genes • the structure of DNA • DNA screening and related issues • various genetic diseases • ethics of genetic screening

18. Homework • Complete Activity 1.2 0n p 21. • Work in groups of five • Complete question 1-6.