In-class Exam #2 21 March 2001
Answer each question as succinctly as possible. You may use the back if you need more space than is provided below the question. Each question is worth 3 pts, unless otherwise noted, for a total of 70 points, which along with your 30 point take-home gives a possible 100 points for this exam. Read each question carefully, and donít hesitate to ask if a question seems unclear.
1. a. What are 2 unique characteristics of bacteria? (2pts)
any 2 of: no internal membrane, very rapid cell division, single circular genome, cell wall of glycans, single-celled
b. What are 2 ways bacteria are beneficial to humans and 2 ways
they are harmful? (4pts)
any 2 of Good: help digest, protection on body surface, nitrogen fixation, decay dead material, produce oxygen
any 2 of Bad: food spoilage, diseases (TB, food poisoning, cavities, STDs), bad breath
2. What is the greatest problem that thermoacidophiles need to overcome to survive where they live, and how do they overcome this problem? (4pts)High temperatures cause their proteins to denature. By using disulfide bonds between cysteines in the same protein to form covalent bonds that hold the 3-D structure together.
3. A person can be infected with HIV (a virus) for many years
before showing any signs of AIDS. What is happening to the HIV in their
body during this time? (4pts)
The HIV has integrated its DNA into the DNA of the host (human). The virus is not being actively replicated, but is replicated along with the host genome.
4. a. What are 2 unique characteristics of plants? (2pts)
any 2 of: have chloroplasts, cell wall of cellulose, growth only at meristem
b. Describe 3 differences between xylem and phloem.
Xylem: water movement, very large-thick walled cells, not use energy to transport, dead at maturity, only move from roots to leaves.
Phloem: sugar movement, small cells, use energy to transport, alive at maturity, can transport in many directions.
c. There are two major parts of seeds that were discussed in class,
what are they, and how are they formed? (4pts)
Embryo from the pollen and egg; endosperm from the pollen and other part of female
5. a. What are 2 unique characteristics of animals? (2pts)
any 2 of: motile, ECM made of protein, get cancer
b. How are the hearts of fish less efficient than those of mammals?
After the blood goes through the gills, there is low blood pressure to the body. Mammals pass blood to the heart after the lungs to increase blood pressure to the body.
c. Why are animals that have exoskeletons generally smaller than
animals with internal skeletons?
Exoskeleton limits size due to weight, and need to molt to grow.
6. a. What are 2 unique characteristics of fungi? (2pts)
any 2 of: cell wall of chitin, during reproduction nuclei are in same cell but do not fuse until later
b. What are 2 ways fungi are beneficial to humans and 2 ways they are
any 2 of Good: decay dead material, produce antibiotics, fermentation, we eat them, mycorrhizae help plants grow.
any 2 of Bad: spoil food, human disease, allergies.
7. a. Cells become cancerous because of mutations that accumulate
in a cell's genome. What are 2 types of mutations that might lead to cancer?
(I am looking for the types of genes that, when they have mutations, can
lead to cancer.) (4pts)
any 2 of: Mutations in genes that control cell-cycle, mutations in genes controlling contact inhibition, telomerase turned on, MDR turned on, mutation in DNA repair mechanism.
b. What are 2 causes of these mutations? (2pts)
any 2 of: radiation, viruses, toxins, replication errors
c. Briefly describe one current cure for cancer, its benefits
and drawbacks. (4pts)
Either: Surgery- if leave behind cancer cells, tumor will regrow
Radiation- damages other cells
Chemotherapy- damages other cells, or need to give high dose due to active MDR
8. a. Identical twins have identical genes, but by the time they
reach adulthood, they neither look nor act identically. Why?
Environment effects phenotypes.
b. The human population is approximately 50% male and 50% female.
50% distribution of Y chromosome, fathers gametes have 50% X chromosome, 50% Y
c. Why are genes that are far apart on a chromosome more
likely to be inherited separately? (4pts)
Genes further apart have more chance for recombination to take place between them.
9. a. If short people only mate with short people, and tall people
only mate with tall people, what will eventually happen to the human species?
Will eventually split into 2 species, divergent evolution.
b. What kind of selection is this?
10. a. What are 3 characteristics of earth 4 billion
years ago that would be different than today?
Any 3 of: no oxygen in air, higher temp, more volcanic activity, higher UV light, no life, higher CO2 levels in air, not many complex molecules
b. Why was the formation of lipids critical for the origin of living
Need to separate inside from outside of cells.