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Principles of Biology I
Exam III, Fall ‘05
Name:_____________________________
Read all of the possible answers for each question before choosing the BEST ANSWER.
1. Mendel chose two true breeding cultivars of the pea for an experiment. One had
purple flowers and the other white. Later, when he had completed his experiment
and was recording the results, these two cultivars would be called:
a. the parental (P) generation.
b. the first filial (F1) generation.
c. the second filial (F2) generation.
d. hybrids.
e. generation X.
2. The height of a human male seems to vary widely with no obvious individual
phenotypes (individuals can be found that represent virtually all different heights
over a rather wide range). This is primarily an example of the phenomenon
called:
a. continuous variation.
b. epistasis.
c. pleiotrophism.
d. independent assortment.
e. environmental effects.
3. The chromosomal theory of inheritance is commonly attributed to:
a. Mendel.
b. Sutton.
c. Chargaff.
d. Messelson and Stahl.
e. Morgan.
4. The arctic fox has a white fur coat in the winter but a reddish brown coat in the
summer. This is an example of:
a. continuous variation.
b. epistasis.
c. pleiotrophism.
d. incomplete dominance.
e. environmental effects.
5. The ultimate source/mechanism for the introduction of new alleles into a species
is:
a. gene flow.
b. founder effects.
c. hybridization.
d. genetic drift.
e. mutation.
6. A time traveler has brought Mendel “back to the future” and he has now accepted
a position at UNT. He decides to continue his work and begins by performing a
dihybrid cross for pea pod shape and plant height. These are the two loci are
located very close to each other on chromosome four and therefore do not assort
independently during meiosis. Unfortunately Mendel does not keep up with the
literature and doesn’t know this. If he properly interprets his new results, Mendel
will now rediscover:
a. epistasis.
b. crossover fixation.
c. linkage.
d. codominance.
e. why he never performed this cross in the 1800’s..
7. Humans cannot tolerate a variable number of chromosomes in a developing
embryo and yet the male embryo has one X chromosome and the female has two.
The X chromosome is also large and carries many genes. We now know that the
female cells compensate for this problem by forming a/an:
a. autosome.
b. centriole.
c. nucleosome.
d. Barr body.
e. inclusion body.
8. A human female with the karyotype XO will:
a. have Klinefelter syndrome.
b. have Turner syndrome.
c. be normal since the second X chromosome isn’t used anyway..
d. have Down syndrome.
e. None of the above are true since monosomic chromosomes are fatal before
birth.
9. Mendel proposed a Law of Independent Assortment. Today we would call the
units that he hypothesized to assort independently:
a. alleles.
b. homozygotes.
c. genes.
d. cultivars.
e. filials.
10. Another term for reproductive success is:
a. natural selection.
b. epistasis.
c. syngamy.
d. fitness.
e. prototrophy.
11. Recently one of the Martian rovers stumbled across the remains of that planet’s
library of natural history. One of the books describes the evolutionary processes
that lead to a now extinct, long-legged animal translated as the akfar. The
ancestors to the akfar apparently received painful scratches on their underbellies
from a very thorny bush then common on the planet. Clearly the animals had to
stretch their legs to the maximum to avoid this painful experience. The book goes
on to describe the fossil record leading to the akfar and explains the progressively
longer legs of each succeeding generation as resulting from the passing on the
stretched legs (longer from all of the stretching) of the parents to the offspring
which in turn stretched them further before passing the even longer legs on to the
next generation. This Martian theory is very similar to an explanation for the
process of evolution described by:
a. Wallace.
b. Lamarck.
c. Sutton.
d. Flemming.
e. Darwin.
12. In a stable population of individuals, the allele frequencies should remain
relatively constant if certain conditions are met. This is the:
a. Hardy-Weinberg principle.
b. theory of natural selection.
c. theory of evolution.
d. first law of Mendel.
e. second law of Mendel.
13. The sickle cell allele is lethal in the homozygote state, but the same allele in
heterozygote form provides resistance to malaria. This is an example of:
a. independent assortment
b. heterozygote advantage
c. homozygote deficiency
d. frequency-dependent selection
e. crossing over
14. A population of flowers under study has a range of colors from white to pink to
dark red. In this case red, pink and white are all the phenotypic result of separate
alleles at the flower color locus. Deer prefer to eat pink flowering plants to the
point where the numbers of pink plants are severely and continuously reduced in
the population. Eventually this yields a population where red and white are
common colors but pink plants are almost never found. This would be an
example of:
a. stabilizing selection.
b. directional selection.
c. disruptive selection.
d. random selection.
e. frequency-dependent selection.
15. Millions of years ago the sole surviving herd of triceratops was astronomically
reduced (struck by a sizeable asteroid, reducing it to only 10 members).
However, the number of these reptiles rebounded over time and the species once
again become common (until a bad experience with an even larger asteroid).
Given these facts, a modern study of genetic diversity in the DNA of post-asteroid
triceratops (recovered from blood sucking insects preserved in amber) might be
expected to reveal that from the point of population genetics, these reptiles
experienced:
a. natural selection.
b. directional selection.
c. the bottleneck effect.
d. diversifying selection.
e. one of those very bad hair days.
16. Which of the following is NOT required to maintain Hardy-Weinberg
equilibrium?
a. random mating
b. no migration
c. no mutation
d. large population size
e. All of the above are required to maintain Hardy-Weinberg equilibrium.
17. The average birth weight of a human baby is 6-7 pounds. Babies with
substantially higher or lower birth weights have a much higher infant mortality
rate (lower survival). This is an example of:
a. epistasis.
b. disruptive selection.
c. directional selection.
d. stabilizing selection.
e. the bottleneck effect.
18. A person is determined to have a blood type of AB. At this locus this person is a:
a. dihybrid.
b. zygote.
c. homozygote.
d. heterozygote.
e. heterokaryon.
19. A red flowered plant is crossed with a white flowered plant. Flower color in this
particular plant exhibits incomplete dominance. The fraction of pink plants in the
F1 generation would be expected to be:
a. 0/4) (zero).
b. 1/4.
c. 2/4 (50%).
d. 3/4.
e. 4/4 (100%).
20. Alternative forms of a character (e.g. round vs. wrinkled peas) are called:
a. genes.
b. hybrids.
c. heterozygotes.
d. alleles.
e. filials.
21. Genes located on the same chromosome are said to be:
a. polygenic.
b. bottlenecked.
c. pleiotropic.
d. linked.
e. epistatic.
22. The expression of human blood groups ia an example of the genetic phenomenon
known as:
a. epistasis.
b. pleotropism.
c. incomplete dominance.
d. codominance.
e. continuous variation.
23. A homozygous dominant plant (PP) is crossed with a homozygous recessive plant
(pp). The F1 generation is then self-crossed to produce the F2 generation. The
phenotypic or Mendelian ratio of the offspring will be:
a. 1:3
b. 3:1
c. 9:3:3:1
d. 9:7
e. 2:2
24. An example of a human genetic disorder involving a male with a Barr body is:
a. Klinefelter syndrome.
b. Down syndrome.
c. Huntington disease.
d. Turner syndrome.
e. muscular dystrophy.
25. A human gene is said to be sex-linked if:
a. it is more common in females than males.
b. it is found on the “Y” chromosome.
c. it is found on the “X” chromosome.
d. it is expressed only in males.
e. it is recessive in males.
26. An allele at one locus affects several phenotypic traits (e.g. cystic fibrosis is
caused by a single defective gene which causes clogged blood vessels, sticky
mucus, salty sweat, liver failure, etc.). This is an example of:
a. continuous variation.
b. codominance.
c. incomplete dominance
d. epistasis.
e. pleiotropic effects.
27. The red flower allele exhibits incomplete dominance over the white flower allele. Using the
Hardy-Weinberg equation (p2 + 2pq + q2 = 1), if the frequency of the red allele in a population
is 0.8, and the frequency of the white allele is 0.2, what is the fraction of plants that will have
pink flowers?
a. 4%
b. 8%
c. 16%
d. 32%
e. 64%
28. If you listen in lecture, according to Dr. Benjamin, that hemophilia in the
European royal families is a clear example of:
a. incomplete dominance.
b. multigenic inheritance.
c. epistasis.
d. genetic warfare.
29. Which of the following properties are NOT properties of the presently accepted
(Watson and Crick) model for DNA structure?
a. Nucleotides are connected by phosphodiester bonds.
b. The two strands are complementary.
c. Adenine pairs with cytosine.
d. The two strands are antiparallel.
e. All of the above are correctly stated properties of the present model.
30. The process of DNA replication is said to be carried out in a semiconservative
manner. This means that:
a. although the individual nucleotides of a strand are held together by
covalent bonds, the two strands of the duplex are held together by weak,
easily broken bonds.
b. only half of the DNA is passed on to the next generation, with the
remainder being discarded as heterochromatin.
c. some of the DNA is replaced by RNA during replication.
d. base pairing rules change each purine position to a pyrimidine, and vice
versa, during the replication process..
e. each daughter duplex has one of the parental duplex strands passed on to
it.
31. The semidiscontinuous nature of the DNA replication process was discovered by:
a. Watson and Crick.
b. Messelson and Stahl.
c. Chargaff.
d. Okazaki.
e. Gurdon.
32. The 3’exonuclease activity of a DNA polymerase is used for:
a. proofreading.
b. nick translation.
c. synthesis.
d. mobility.
e. All of the above are dependent upon this activity.
33. The protein which binds to single-stranded DNA to keep it protected and to
prevent base pairing is called:
a. gyrase.
b. helicase.
c. SSB.
d. replicase.
e. ligase.
34. The enzyme responsible for primer removal during DNA replication in E. coli is
called:
a. helicase.
b. gyrase.
c. DNA polymerase I.
d. DNA polymerase III.
e. DNA ligase.
35. A pea plant is determined to be Aa at a certain locus. In this case Aa is
considered to be its:
a. phenotype.
b. genotype.
c. filial.
d. hybrid makeup.
e. Punnett square.
36. Mendel’s first law of heredity, demonstrated/proven by the monohybrid cross
data, was:
a. the law of probability.
b. the law of dominance.
c. the law of segregation.
d. the law of inheritance.
e. the law of independent assortment.
37. The British doctor who observed that an unusual metabolic disorder was inherited
in families in a Mendelian fashion and therefore made an early connection
between the gene and the enzyme was:
a. Tatum.
b. Garrod.
c. Gurdon.
d. Sutton.
e. Griffith.
38. During the process of making a polypeptide, the new amino acid enters the
ribosome’s:
a. rbs.
b. “P” site.
c. “A” site.
d. “E” site.
e. anticodon.
39. The template used by a ribosome making a polypeptide is called:
a. an mRNA.
b. a tRNA.
c. an rRNA.
d. an rbs.
e. the sense strand of the DNA duplex.
40. The sequence of nucleotides commonly found at the –10 position of an E. coli
promoter is:
a. TATAAT.
b. AAAAAA.
c. TTGACA.
d. called the rbs.
e. ATG.
41. A hairpin structure with a GC-rich stem followed by a string of U’s is commonly
associated with:
a. transcriptional terminators.
b. promoters.
c. the rbs.
d. the transcription bubble.
e. rRNA molecules.
42. The process of making a polypeptide using an RNA template is called:
a. phosphodiester synthesis.
b. translation.
c. transcription.
d. replication.
e. transition.
43. The enzyme that eliminates primers during DNA replication is:
a. DNA polymerase I.
b. primase.
c. DNA polymerase III.
d. helicase.
e. DNA ligase.
44. The codon AUG in protein synthesis is read as:
a. stop.
b. start.
c. an internal amino acid, but not start or stop.
d. release the polypeptide.
e. start transcription here.
45. The region of a gene (DNA) where the RNA polymerase binds to begin gene
expression is called the:
a. origin.
b. ribosome binding site.
c. promoter.
d. initiator site.
e. P site.
46. The individual(s) who obtained the first X-ray diffraction data from DNA crystals
that showed it was a helix of uniform diameter was/were:
a. Watson and Crick.
b. Erwin Chargaff.
c. Rosalind Franklin.
d. P. A. Levine.
e. Messelson and Stahl.
47. The correct model of the structure of a DNA molecule was elucidated (solved) by:
a. Franklin and Wilkins.
b. Linus Pauling.
c. Hershey and Chase.
d. Erwin Chargaff.
e. Watson and Crick.
48. During DNA replication, the double helix is opened by the enzyme:
a. DNA gyrase.
b. DNA polymerase I.
c. Primase.
d. DNA polymerase III.
e. helicase.
49. During DNA replication, the enzyme DNA ligase:
a. connects short segments of DNA together.
b. connects the first few nucleotides of each new molecule.
c. Opens the helix at the replication fork.
d. removes the “over winding” caused by the opening of the DNA helix.
e. binds to single-stranded regions at the fork to keep them from reforming
base pairs.
50. The two strands of a DNA molecule are held together by:
a. phosphodiester bonds.
b. ionic bonds between the phosphates.
c. hydrophobic interactions between the bases.
d. hydrogen bonds.
e. aminoacyl bonds.
51. Messenger RNAs are synthesized by:
a. ribosomes.
b. DNA polymerases.
c. RNA polymerase.
d. promoters.
e. aminoacyl tRNA synthetases.
52. The enzymes that connect the amino acids to the tRNAs are called:
a. aminoacyl tRNA synthetases or activating enzymes.
b. promoters.
c. ligases.
d. RNA polymerases.
e. elongation factors.
53. A common transcriptional terminator in a bacterial system would be:
a. a GC-rich stem structure followed by a string of U’s in an mRNA.
b. UAG.
c. a transcription factor.
d. a releasing factor.
e. The sequence TAA at the 3’end of a gene.
54. A spliceosome is a complex of nucleic acid and protein that:
a. transcribes mRNAs in bacteria.
b. is involved in the process of protein synthesis (translation) in both
prokaryotes and eukaryotes.
c. ss considered a transcription factor found in eukaryotes.
d. is involved in DNA methylation in eukaryotes.
e. is involved in RNA processing in eukaryotes.
55. Two white-kernelled true-breeding strains of corn are crossed and surprisingly
give F1 plants that all have purple kernels. A selfing of the F1 plants yields F2
generation plants that have a ratio of 9 purple kernelled to 7 white kernelled. This
is likely an example of:
a. incomplete dominance.
b. blending.
c. codominance.
d. epistasis.
e. pleiotropic effects.
56. Nearly all mRNAs in eukaryotes end in the sequence:
a. AAA200.
b. UAA.
c. AUG.
d. TATA
e. TTGACA