Human Biology, Fourth Quiz: 4 April 2000

A. Multiple choice questions: 0.5 points each.

• 1. Name two bacterial sexually transmitted diseases.

  (a) hepatitis B and herpes.	(b) vaginitis and pubic lice.
  (c) syphilis and chlamydia	(d) none of the above.

• 2. Which of the following is not a characteristic of HIV infections?
  • (a) a long latency period before the most serious symptoms arise.
  • (b) suppression of immune response to secondary pathogens.
  • (c) transmission through insect vectors is common.
  • (d) the majority of those currently infected live in Africa.
  • (e) most cases in the US up through the mid-1980's were found among homosexual males and intravenous drug users.
• 3. When a sperm contacts an oocyte
  • (a) it releases digestive enzymes.
  • (b)it may attach to receptors on the vitelline envelope.
  • (c) if the membranes of the two cells fuse, the sperm nucleus can enter the oocyte.
  • (d) if it is the first one to enter the oocyte, no others will be able to do so.
  • (e) all of the above.
• 4. In development, the ability of a chemical or tissue to influence the fate of nearby cells is called

  (a) cleavage	(b) cytoplasmic streaming	(c) induction
  (d) reduction	(e) interaction

• 5. After 3 months of development
  • (a) the fetus is over 12 inches long.
  • (b) sexual differentiation has occurred.
  • (c) the fetus drops so his or her head lies against the cervix.
  • (d) dilation of the cervix often begins.
  • (e) the fetus is essentially developed and only growth remains.
• 6. In which stage of the cell cycle is chromatin uncondensed rather than organized into chromosomes?

  (a) prophase	(b) anaphase	(c) early interphase
  (d) metaphase	(e) telophase

B. Fill in the blanks: 0.5 points each.

• 7 Typically, viruses have an inner core of _________ and a capsid of __________.
  
  
• 8. The ______________ membranes include the ___________,
  the amnion, the allantois, and the yolk sac.
  
• 9. According to a popular genetic theory of aging, antioxidant enzymes that detoxify __________,
  which are reactive compounds that tend to react with DNA and other cellular macromolecules to produce damage, help to slow the aging process.
  

C. Definitions: 0.5 points each.

Provide a one-sentence definition for each word or phrase.

• 11. antibiotic.
  
  
  
• 12. morphogenesis (in the context of development).
  
  
  
• 13. episiotomy.
  
  
  

D. Short answers: 1 point each.

• 13.Arrange the stages of development in the correct order (earliest to latest as 1-5):

  blastula	morula	zygote	neurula	gastrula

  
  
• 14. Which of the embryonic (germ) layers will produce the following types of tissues?

  muscles	skin epidermis	pancreas	bone, cartilage	nervous system

  
  

D. Full-paragraph answer: 2 points.

Answer either of the following two questions with a short paragraph. If you answer both, you will receive credit for neither.

• 15. The early mitotic divisions of the zygote are called cleavage. The first two cell divisions are along the axis determined by two poles called the animal and vegetal poles. These poles are defined by uneven distributions of components of the cytoplasm. The first four cells get material from both poles. The third cleavage is perpendicular to the axis and the daughter cells include cytoplasm from either the animal or vegetal pole. If one were to extract one cell from a 4-cell embryo and attempt to culture it under conditions that allow for differentiation and development, would one expect that single cell to be able to develop into an entire animal? What if one extracted one cell from an 8-cell embryo? Explain.
  
• 16. Many AIDS patients in the US receive a treatment regimen involving several drugs, including azidothymidine (AZT), which is an analog of an RNA base; and ritonavir, which is a peptidomimetic, i.e. a compound that resembles a short stretch of protein. Each of these compounds binds to and inhibits a specific viral enzyme necessary for the survival and proliferation of the virus. Name the relevant enzymes. Why would you expect such multidrug therapy to work better than a therapeutic regimen involving only one of the two?