AP Biology Free-Response Week 9 (September 29, 2008)
Use the tips for answering free response questions found on the FSHS AP Biology website. Each question should be answered in essay form with complete sentences and labeled clearly. After completing answer, use a highlighter to emphasize main points and clarifying details of your response. Your free response questions will comprise a major test grade each nine weeks.
1.A mule is the offspring of a horse and a donkey. A donkey sperm contains 31 chromosomes and a horse egg cell 32 chromosomes, so the zygote contains a total of 63 chromosomes. The zygote develops normally. The combined set of chromosomes is not a problem in mitosis, and the mule conbines some of the best characteristics of horses and donkeys. However, a mule is sterile; meiosis connot occur normally in its testes or ovaries. Explain why mitosis is normal in cells containing both horses and donkey chromosomes but the mix set of chromosome interferes with meiosis.
2. Red blood cells, which carry oxygen to body tissues, live for only about 120 days. Replacement cells are produced by cell division in bone marrow. How many cell divisions must occur each second in your bone marrow? How many cell divisions must occur each second in your bone marrow just to replace red blood cells? Here is some information to use in calculating your answer: There are about 5 million red blood cells per cubic millimeter of blood. An average adult has about 5 L (5,000 cm³) of blood. (Hint: What is the total number of red blood cells in the body? What fraction of them must be replaced each day if all are replaced in 120 days?)
3.Bacteria are able to divide on a much faster schedule than eukaryotic cells. Some bacteria can divide every 20 minutes, a rapidly developing embryo is about once per hour, and most cells divide much less often than that. State several testable hypotheses explaining why bacteria can divide at a faster rate than eukaryotic cells.
4.A portion of a specific DNA molecule consists of the following sequence of nucleotide triplets.
TAC GGA CTT GGG TCC
The DNA sequence codes for the following short polypeptide.
Methionine-leucine-glutamic acid-proline-arginine
Describe the steps in the synthesis of this polypeptide. What would be the effect of a deletion or an addition in one of the DNA nucleotides? What would be the effect of a substitution in one of the nucleotides?