BIOLOGY 1400

Fall 2002: Lecture Exam 2

This exam consists of 50 multiple-choice questions. Each one has only one right answer. Read each question and all possible answers carefully before answering. Please mark your answers on the Scantron form provided, using only #2 lead pencil. If you erase an answer, make sure you erase it fully, or the machine may mark it incorrect. Check carefully to ensure that your answers are on the correct rows on the Scantron form.

Turn in both the Scantron form and the test paper when you are finished. Make sure your name is on both. You may write on the test paper if you wish, but anything you write on the test paper will not be graded. Good luck.

1. Parkinson's disease is a loss of motor control that results from the death of nerve cells in a certain region of the brain. An experimental treatment of Parkinson's disease involves transplanting stem cells into the affected part of the brain. Stem cells are cells which

have not specialized

2. Mature nerve cells have lost the ability to undergo ____, which stem cells still can do.

differentiation

3. Nerve cells can transmit messages in the brain, in part, because they have molecules on the outside of the cell membrane that can"receive" chemical signals from other nerve cells. These are called receptors, and they're proteins, meaning that they're made from ___.

amino acids

4. Many drugs, poisons and toxins interfere with the action of nerve cell receptors. Cocaine, for instance, blocks the active site on a particular receptor protein, because cocaine molecules fit into the active site just as well as the intended "chemical messenger" does. Taking cocaine would create an example of

competitive inhibition

5. Some people might make faulty nerve cell receptor proteins because of a "copying error" in their DNA, also known as a/an

mutation

6. A human disease called congenital myasthenic syndrome (CMS) results from a faulty nerve receptor protein. People with CMS tire easily and develop weak muscles. (CMS is sometimes lumped together with many other similar muscle diseases as a form of "muscular dystrophy", of Jerry Lewis Labor Day Telethon fame.) It can happen that two people who don't have CMS may have a child who does have CMS. This must mean that

CMS is caused by a recessive gene.

7. Two people who don't have CMS marry, and their first child has CMS. They come to you for counseling, wanting to know whether their next child will be healthy. What do you tell them?

Each child has a 25% chance of having CMS.

8. Cells in the human liver don't make the same receptor proteins that nerve cells do.

This is because liver cells have "switched off" that part of their DNA.

9. Rattlesnake venom contains toxic proteins that interfere with nerve cells. Some people who get bitten by rattlesnakes try to treat themselves with strong electric shocks. (This doesn't really work very well.) The idea is that the electricity will case the rattlesnake venom proteins to denature-meaning that they will

change shape

10. The proteins in rattlesnake venom are chains of amino acids that tend to attract each other to form shapes such as alpha-helices and beta-sheets. This describes their

secondary structure

11. One rattlesnake protein is actually made up of six different chains of amino acids, each folded up separately and then attached to each other. This describes their

quaternary structure

12. Suppose a terrorist decided to make a huge amount of rattlesnake venom to use as a poison. What would be the easiest way?

Insert the venom gene into a bacterium and grow the bacteria.

13. A stretch of DNA reads: TTGACCCAAGGT. What must the complementary DNA strand be?

AACTGGGTTCCA

14. TTGACCCAAGG is the DNA strand that actually codes for a protein. That strand is called the

sense strand

15. Which of the following is a way to divide the DNA strand into codons?

TTG ACC CAA GGT

16. DNA is made up of two strands of monomers known as

nucleotides

17. The letters A, C, G and T in question 13 refer to the specific parts of the monomers known as the

bases

18. Proteins are actually made

on ribosomes.

19. Molecules known as transfer RNAs

"carry" specific amino acids to a ribosome

20. The two strands of a DNA molecule are fastened to each other by weak, breakable links called

hydrogen bonds.

21. Many drugs have the effects that they do because they mimic a naturally occurring compound within the body (these are called analogs). A drug called ddI (sold under the trade name Videx®), shown at right, is a nucleotide analog -- it resembles a nucleotide, but it doesn't work in the same way that the body's nucleotides do. Dosing a cell with ddI would impair the cell's ability to make DNA and RNA

22. Why is ddI used to treat AIDS and other viral diseases?

Virus-infected cells make viral DNA or RNA.

23. ddI has severe side effects (which is why you wouldn't want to treat a common head cold with it). Its side effects result from the fact that cells full of ddI cannot

replicate their own DNA.

24. The result of ddI's effects on the body's cells is that cells will

not undergo mitosis.

25. Another molecule, domoic acid, is toxic to humans (it may be found in shellfish and causes a type of poisoning in people who eat tainted shellfish). Domoic acid is an amino acid analog, meaning that cells try to use it to make ___ in the process of ___, but fail.

proteins; translation

The rock group Creed played a concert in Little Rock on September 24, 2002. Imagine that, nine months later, Brytnee Sue McFadden, an unusually persistent and energetic groupie from Searcy, gives birth to a healthy baby boy. She promptly sues the group for child support, but is unable to specify which of the four band members is in fact the father.

26. Brytnee Sue has type AB blood. Just knowing this, what blood type do you know that her baby will not have?

Type O
Her baby must have received either an A or a B from her, if she's AB.

27. As it happens, the baby has type A blood. Which of the four members of Creed's current touring lineup is not the father?

Any of the four members could be the father.
If she's AB and the baby's A, then the baby must have received that A allele from her. The baby could then have the AA or the AO genotype, meaning that the father must have had either an A or an O allele to pass on to the kid. Unfortunately, all four members either have an A, have an O, or could have an O.

28. Mark Tremonti, the guitarist, swears that the kid can't be his. What evidence would get him off the hook?

Both his parents have type AB blood.
He's got type B blood. He could have the genotypes BB or BO. If he is BO, then he could have contributed the O allele to the baby, who got an A allele from Mom. But if he's BB, he's off the hook. If both his parents have AB blood, then he must have received the B allele from each parent, making him BB.

29. Blood typing may not be enough to tell who the father of Brytnee Sue's baby is. If it's not, it would be possible to look at inherited variations in the length of certain DNA sequences called

RFLPs

30. The DNA sequences that would be examined using the modern technique mentioned in question 29 are often called "junk DNA." Why is this is a misleading name?

We're not sure whether they have a function or not.

31. This new technique pinpoints Scott Stapp, lead singer and lyricist for Creed, as the father of Brytnee Sue's baby. (Apparently his rendition of "With Arms Wide Open" went a little too far that night.) Anyway, now that we know this, what must the baby's genotype be?

AA
Stapp is AB, meaning his kid must inherit either an A or a B from him. We know the baby's A and inherited one A allele from Mom; the baby must have inherited a second A from Stapp.

32. The First Law of Thermodynamics states that

energy can neither be created nor destroyed.

33. The disease Duchenne's muscular dystrophy is far, far more common in boys than in girls, although it's possible for girls to have it. This probably means that the gene for this disease is

on the X chromosome.

34. A boy with Duchenne's muscular dystrophy

inherited it from his mother.

35. Which of these is an example of activation energy?

The spark that sets off a forest fire.

36. A cell that is haploid

has one of each type of chromosome.

37. If a diploid cell undergoes meiosis, the result is

four haploid cells.

38. When you dissolve the chemical ammonium nitrate in water, the water turns colder. This is because heat energy is being taken out of the surroundings by a chemical reaction. This reaction is

endothermic.

39. In bell pepper plants, genes determine whether the bell pepper fruit loses its green color or not. Some bell peppers keep their green color until they're picked. Others lose their green pigment as they ripen. Suppose you crossed two green bell pepper plants, and some of the offspring stayed green but others changed color. This would mean that the gene for staying green was ___ to the gene for losing green pigment.

dominant
If the green gene was recessive and the not-green gene was dominant, then both parents would have to have the genotype gg -- and all of their offspring would be gg and would be green. The fact that two green peppers can have not-green offspring must mean that the not-green gene can "hide" in one generation but appear in the next. In other words, non-green is recessive (g) and green is dominant (G).

40. If we crossed a homozygous green bell pepper with a heterozygous green bell pepper, what would we get?

All of the offspring would stay green.
The cross GG x Gg would make half the offspring GG and half Gg -- and all would look green.

41. A second set of genes codes for either red or yellow pigments in the bell pepper. Green color can cover up yellow, but if a plant produces both green and red together it looks purple (yes, there are purple peppers!) If we represent the red gene as R and the yellow as r, and abbreviate the genes that affect greenness as G and g, which of these genotypes would belong to a red bell pepper?

ggRr

42. Suppose we crossed a purebred red bell pepper with a purebred yellow bell pepper. The offspring would all look the same; they would look

red
Purebred red = ggRR. Purebred yellow = ggrr. Cross 'em, and all the offspring are ggRr.

43. Now suppose we took one of the offspring from the cross in question 42, and we crossbred it with a plant whose genotype was Ggrr. How many kinds of offspring would that cross produce?

Red, yellow, purple and green.
Why? We're crossing ggRr with Ggrr. The ggRr parent can pass on two allele combinations: gR and gr. The Ggrr parent can pass on two allele combinations: Gr and gr. Put these on a 2x2 Punnett square, and you'll see that there are four possible genotypes of the offspring: GgRr (purple), ggRr (red), Ggrr (green), and ggrr (yellow).

44. A plant called Japanese four-o'clock may produce either red or white flowers. This is caused by a single gene that determines the flower color. This gene comes in two forms called

alleles

45. If you cross a Japanese four-o'clock plant with red flowers with one that has white flower, you get a bunch of plants with pink flowers. At first glance, this looks like support for a discredited theory of heredity which stated that organisms have traits that are the "averages" of their parents' traits. This theory was called

blending inheritance.

46. However, flower color in Japanese four-o'clocks is an example of incomplete dominance. This means that, if you cross two pink-flowered plants, you should get

25% red-flowered, 50% pink-flowered, and 25% white-flowered plants.

47. Gregor Mendel remains famous for

showing the existence of genes.

48. One of the minerals called zeolites will turn wood alcohol (methanol) into high-octane gasoline. (Mobil Corporation invented it in the 1970s, and it's being used in some places to generate fuel.) The zeolite causes methanol molecules to link together, but it itself is not used up in the reaction. This means that this zeolite

is a catalyst.

49. You go to the Library and find a book with a recipe for bread that sounds really tasty, and you decide that you'd like to try baking it. Unfortunately, the book's in the Reference section and can't be checked out. So you photocopy the page with the recipe and take the copy out of the Library to your kitchen. What biological process is this like?

transcription

50. The mascot of the UCA football team is the

Bears