STUDY GUIDE, CON’T
Test: DNA & MEIOSIS v. MITOSIS
Be able to answer the following questions:
1. List and describe the parts of a nucleotide? A nucleotide is made of three components. The sides are alternating sugar and phosphate molecules. The third element is a nitrogenous base that is attached to the sugar molecule. There are four bases: adenine, thymine, cytosine, and guanine.
2. Which bases pair together in a DNA molecule? Adenine always pairs with thymine, and guanine always pairs with cytosine.
3. What shape was suggested by Rosalind Franklin’s X-ray images? Franklin’s images suggested that the shape of DNA was a double helix or spiral shape.
4. Explain what is meant by the statement, “DNA unites all organisms”. DNA is the same structure for all living organisms. Sugar and phosphates alternate along the sides of the ladder and the rungs are composed of four bases; A with T and G with C.
5. If a sample of DNA were found to contain 20% cytosine, what percentage of guanine would be in this sample? Why? It would contain 20% guanine because C pairs with G (always!) and this was revealed through research by Erwin Chargaff.
6. List the three types of mutations. How do they differ? The three types of mutations are: DELETION: a base is left out; INSERTION: an extra base is included in the strand; and SUBSTITUTION: a different base is used in place of the original one in the sequence.
7. What causes a recessive disorder? A recessive disorder is caused when an organism inherits two recessive alleles for a disease. You have to have both alleles (one from Mom and one from Dad) in order to develop the disease. If you only have one allele you will be a carrier; you will not develop the disease nor will you ever have any symptoms of the disease.
8. How is genetic engineering different from selective breeding? Genetic engineering can change the DNA sequence of an organism by splicing in DNA from another organism. Selective breeding is the selection of organisms with desirable traits that are bred to produce offspring with the desired traits.
9. Mutations can occur in sex cells or in body cells. In which cell type might a mutation be passed from generation to generation? Explain. Mutations that occur in the sex cells (eggs and sperm) will be passed from generation to generation because the sex cells are what form the DNA of the next generation.