2. DNA is an abbreviation for d eoxyribo n ucleic a cid. -------------------------------------------------------- *It is formed in the cells of all living things,including the human body. *The DNA is a very long molecule and is found in the nucleus of cells

3. DNA consists of three basic components: A. A sugar (pentose sugar) ~ dexoyribose which is oxygen less of the ribose sugar B. Phosphate group ~ chemically reactive

4. C. Organic nitrogenous base ~ 4types of nitrogenous base, 2 purines and 2 pyrimidines ~ purines consists of adenine (A) and Guanine(G) ~ pyrimidines consist of cytomsine(C) and thymine (T)

6. In 1962, James Watson (from America) and Francis Crick (from Britain) discovered the structure of DNA. They were awarded a Nobel Prize.

7. (A) The sequence of bases in DNA provides the genetic code to give information to control the cell activities and is specific to each species.

8. (B) The complementary relationship of the bases in the DNA molecule enables the DNA to replicate (make an exact copy) so that the same genetic information can be passed to the offspring. The type of protein and enzyme is characteristic of a species of organism.

10. Chromosomes are made up of proteins (e.g.histones) and nucleic acid (DNA and RNA). The nucleic acids carry the genetic code or genetic formation.

11. Some interesting information about DNA Genetic engineering is an unnatural insertion of a foreign sequence of genetic codes in the midst of the orderly sequence of genetic codes of the recipient, developed through millions of years.

12. Cloning is one aspect of genetic engineering, the part that allows scientists to use a variety of methods to duplicate copies of already existing organisms or genetic material. But the term "genetic engineering" is much broader, encompassing a wide range of procedures designed to alter genetic material, not only copying genes, but in some cases, making completely new proteins.

14. (1) Induced mutation can be induced artificially to occur at a higher rate by applying mutagenic agents (mutagens ). For example: (a) Chemical mutagens - nitrous acids, base analogues,  mustard gas, ethyl urethane  formaldehyde. (b) Physical mutagens - X rays,  ultra-violet rays,  cosmicrays  atomic radiation.