Biology 204
Principles of Biology I
A. Definition/Comparison Questions
Instructions: In your own words, define the pairs of terms given below. Write in complete sentences, stating the differences and relationships between the two terms, and give specific examples where appropriate. A complete answer usually requires four to eight sentences.
Each question is worth four marks, for a total of 40 marks.
1. centriole / kinetochor
2. cleavage furrow / cell plate
3. allele / locus
4. RNA primer / DNA polymerase
5. guanine / cytosine
6. translation / anticodon
7. operator / promoter
8. conjugation / transformation
9. RFLPs / Southern blot analysis
10.pleiotropy / polygenic inheritance
B. Short Answer/Short Essay Questions
Instructions: Answer each of the questions given below in your own words. Write in complete sentences where appropriate. A complete answer usually requires one to two sentences per mark, so a three-mark question would be answered in three to six sentences. This section is worth a total of 40 marks.
(4 marks) 1. Explain how CDKs regulate cell division.
(4 marks) 2. Explain the role of transposable elements in eukaryotes.
(8 marks) 3. Using the following DNA template strand sequence, answer the
questions that follow:
3’–TGCAGGAAGCTACATTAG–5’
a. What is the mRNA sequence?
b. What is the final sequence of amino acids in the peptide produced?
c. If the sequence is mutated so that adenine at position 11 is replaced with uracil, how will the peptide be affected? What kind of a mutation is this?
(5 marks) 4. a. What is an operon?
b. How do inducible operons (e.g., the lactose operon) and repressible operons (e.g., the tryptophan operon) benefit a bacterial cell?
(5 marks) 5. Explain the possible role of telomerase in cellular aging and in cancer
formation.
(6 marks) 6. a. Draw a diagram to show what could happen during meiosis that
would result in an egg with two X chromosomes.
b. If this egg is fertilized and develops, what are the possible karyotypes of the offspring?
(6 marks) 7. A female yellow Labrador retriever homozygous for coat colour
(bbee) is mated with a male black lab. They have two chocolate
puppies, three black puppies and one yellow puppy. What is the
genotype of the father? Use Punnett squares to show your reasoning.
(2 marks) 8. What is a proteome, and why is it studied in addition to (or instead
of) the genome?
C. Multiple Choice Questions
Instructions: Select the single best answer to each of the questions given below. Each question is worth one mark, for a total of 30 marks.
1. A zygote contains the ________ complement of chromosomes.
a. haploid
b. diploid
c. polyploid
d. spermatogenesis
e. none of these
2. How is the nucleoid of a bacterial cell replicated?
a. The linear DNA molecule is replicated from multiple origins of replication bidirectionally.
b. The linear DNA molecule is replicated from one origin of replication bidirectionally.
c. The circular DNA molecule is replicated from multiple origins of replication bidirectionally.
d. The circular DNA molecule is replicated from one origin of replication bidirectionally.
e. The circular DNA molecule is replicated from one origin of replication unidirectionally.
3. Some cats have calico coats. These result from
a. polygenic inheritance.
b. epistasis.
c. pleiotropy.
d. inactivation of the X chromosome.
e. independent assortment.
4. A male human with normal vision is mated with a colour blind woman. If they have children together, what is the probability that they will have a colour blind daughter?
a. 1
b. 0.75
c. 0.5
d. 0.25
e. 0
5. Which of the following is NOT correct about bacterial conjugation?
a. F– cells do not contain the F factor.
b. Bacterial conjugation results in an exchange of genes between two bacterial cells.
c. Genes on the F factor code for sex pili.
d. Genes can be transferred from the donor to the recipient.
e. Hfr cells can produce sex pili.
6. In generalized transduction, a bacterium obtains DNA from a virus as a result of a lytic cycle. The bacterium will
a. survive.
b. harbour a prophage.
c. die immediately.
d. reproduce for a few generations, until the prophage becomes virulent.
e. contain virus nucleic acid.
7. A repressible operon is usually controlled by
a. an inactive repressor that allows the operon to be in the “on” state.
b. the supply of the precursor product for the enzymes.
c. an inactive repressor that keeps the operon in the “off” state.
d. tryptophan.
e. being turned “on,” usually by the end product of the pathway.
8. A karyotype reveals that an individual is XYY. Based on your knowledge of human genetics, you conclude that this individual is phenotypically
a. female and has unusual physical features.
b. female and is sterile.
c. female and is fertile.
d. male and is sterile.
e. male and is fertile.
9. Translocation occurs when
a. part of a chromosome breaks off and attaches to a nonhomologous chromosome.
b. part of a chromosome breaks off and attaches to a homologous chromosome.
c. crossing-over events occur.
d. genes move from one area on a chromosome to another area on the same chromosome.
e. a Y chromosome replaces an X chromosome in a female cell.
10.In a plant cell, cytokinesis begins with the formation of
a. an aster.
b. a mitotic spindle.
c. a Golgi complex.
d. a cell wall.
e. a cell plate.
11.In a human cell at prophase I, there are ________ tetrads.
a. 92
b. 46
c. 23
d. 2
e. 4
12.In which phase are chromosomes least condensed?
a. metaphase
b. prophase
c. anaphase
d. interphase
e. telophase
13.Translation is the process whereby the ________ moves in order
to place the tRNA bound to the growing polypeptide chain in
the ________ site, thereby freeing the ________ site for a new
aminoacyl-tRNA.
a. mRNA; A; P
b. ribosome; P; A
c. tRNA; P; A
d. ribosome; A; P
e. tRNA; A; P
14.Which of the following statements about DNA is FALSE?
a. DNA is capable of forming many different sequences.
b. DNA contains thymine instead of uracil.
c. DNA is double-stranded in eukaryotic cells.
d. DNA is single-stranded in prokaryotic cells.
e. DNA contains the sugar deoxyribose.
15.Binary fission occurs when
a. mitosis takes place without cytokinesis.
b. homologous chromosomes have already paired.
c. the cyclin-Cdk complex is no longer phosphorylating enzymes.
d. the cell cycle is out of control.
e. a prokaryotic cell reproduces.
16.“Sticky ends” are
a. the single-stranded ends of a DNA segment created by some restriction enzymes.
b. a problem in recombinant DNA technology because they form loops of single-stranded DNA.
c. double-stranded ends of a DNA segment created by some restriction enzymes.
d. sites of the origin of replication in prokaryotes.
e. sugar molecules that are bound to the ends of a DNA fragment.
17.Enzymes called ________ form breaks in DNA molecules to prevent overtwisting in the DNA helix during replication.
a. topoisomerases
b. single-strand binding proteins
c. DNA polymerases
d. RNA polymerases
e. DNA ligases
18.What is the probability that two lizards that are heterozygous for striped tails (Ss) will produce an offspring that is homozygous for
no stripes (ss) on its tail?
a. 1
b. 1/2
c. 1/4
d. 1/8
e. 0
19.Crossing over occurs in which phase of mitosis?
a. metaphase
b. anaphase
c. prophase
d. telophase
e. none of the above
20.Genes that encode proteins that are always needed are called
a. repressible genes.
b. promoter genes.
c. constitutive genes.
d. inducible genes.
e. operons.
21.A polyribosome is
a. a complex of many ribosomes and an mRNA.
b. a complex of many ribosomes in eukaryotes.
c. an initiation complex in eukaryotes.
d. an elongation complex in eukaryotes.
e. a complex of a ribosome with its two subunits and several mRNAs.
22.Which of the following statements concerning the cell cycle is FALSE?
a. CDKs are involved in the regulation of the cell cycle.
b. External factors are involved in the regulation of the cell cycle.
c. CDKs are active only when they bind to cyclins.
d. The amount of CDKs changes during the cell cycle.
e. Several types of cyclin regulate different phases of the cell cycle.
23.How does the first nucleotide at the 5’ end of a new mRNA chain differ from the other nucleotides in the chain?
a. The first nucleotide is always a uracil.
b. The first nucleotide is always a cytosine.
c. The first nucleotide retains its triphosphate group, while the others do not.
d. The first nucleotide does not retain its triphosphate group, while the others in the chain do.
e. The first nucleotide is always a modified cytosine.
24.A chromosome has the genes U, V, W, and X. They have been shown to have the following crossover frequencies: U and V: 2%; U and
W: 9%; U and X: 7%; V and W: 7%; V and X: 5%; and W and X: 2%. What is the sequence of the genes on the chromosome?
a. W-X-V-U
b. U-X-V-W
c. X-W-U-V
d. V-U-W-X
e. none of the above
25.Why does DNA synthesis only proceed in the 5’ to 3’ direction?
a. Because DNA polymerases can only add nucleotides to the 3’ end of a polynucleotide strand.
b. Because the 3’ end of the polynucleotide molecule is more electronegative than the 5’ end.
c. Because that is the direction in which the two strands of DNA unzip.
d. Because that is the only direction that the polymerase can be oriented.
e. Because the chromosomes are always aligned in the 5’ to 3’ direction in the nucleus.
26.Which of the following represents the sequence of events during mitosis?
a. prophase → metaphase → anaphase → telophase
b. interphase → metaphase → anaphase → telophase
c. anaphase → telophase → metaphase → interphase
d. interphase → prophase → anaphase → metaphase
e. metaphase → telophase → anaphase → prophase
27.Random segregation refers to
a. crossing over.
b. regulation of mitosis.
c. events during transduction.
d. Barr bodies.
e. paternal and maternal chromosomes.
28.Where is the amino-acid binding site located on the tRNA molecule?
a. in the middle of the loop
b. at the 3’ end of the molecule
c. in the first loop
d. along the longest stretch of base pairing in the molecule
e. at the 5’ end of the molecule
29.During mismatch repair of DNA, the repair enzyme
a. will remove several nucleotides on both DNA strands.
b. will remove several nucleotides on one DNA strand.
c. will remove only the mismatched nucleotide.
d. will remove the mismatched nucleotide, and the same enzyme will replace it with the correct nucleotide.
e. is unable to detect mutations.
30.Which of the following is TRUE regarding alternative splicing?
a. It is very uncommon in humans.
b. One strand of DNA can produce different mRNAs.
c. Introns are often absent.
d. As a result, the same proteins are produced in different cell types.
e. All exons are used to produce m-RNA.
— End of Assignment 2B —
