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Biology 204

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Biology 204
Principles of Biology I
Assignment 2B
For students with first names starting with the letters H to N.
This assignment is graded out of 110 points, and is worth 10% of your final 
mark. Please submit this assignment after you have completed Chapter 16 and 
before you write the final exam.

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.
2. centriole / kinetochor
cleavage furrow / cell plate
allele / locus
RNA primer / DNA polymerase
guanine / cytosine
translation / anticodon
operator / promoter
conjugation / transformation
RFLPs / Southern blot analysis
pleiotropy / polygenic inheritance

Principles of Biology I

1

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 three­mark 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.
and in cancer 
formation.

Explain the possible role of telomerase in cellular aging 

(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?

2

Biology 204

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.
2. A zygote contains the ________ complement of chromosomes.
a.

haploid

b. diploid
c.

polyploid

d. spermatogenesis
e.

none of these

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.

Some cats have calico coats. These result from
a.

polygenic inheritance.

b. epistasis.
c.

pleiotropy.

d. inactivation of the X chromosome.
e.

independent assortment.

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.

Principles of Biology I

0

3

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.

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.

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.

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.

4

male and is fertile.

Biology 204

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.

crossing­over 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.

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.

In a human cell at prophase I, there are ________ tetrads.
a.

92

b. 46
c.

23

d. 2
e.

4

In which phase are chromosomes least condensed?
a.

metaphase

b. prophase
c.

anaphase

d. interphase
e.

Principles of Biology I

telophase

5

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 
aminoacyl­tRNA.
a.

mRNA; A; P

b. ribosome; P; A
c.

tRNA; P; A

d. ribosome; A; P
e.

tRNA; A; P

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 double­stranded in eukaryotic cells.

d. DNA is single­stranded in prokaryotic cells.
e.

DNA contains the sugar deoxyribose.

Binary fission occurs when
a.

mitosis takes place without cytokinesis.

b. homologous chromosomes have already paired.
c.

the cyclin­Cdk complex is no longer phosphorylating enzymes.

d. the cell cycle is out of control.
e.

a prokaryotic cell reproduces.

“Sticky ends” are
a.

the single­stranded ends of a DNA segment created by some 
restriction enzymes.

b. a problem in recombinant DNA technology because they form loops 
of single­stranded DNA.
c.

double­stranded ends of a DNA segment created by some restriction 
enzymes.

d. sites of the origin of replication in prokaryotes.
e.

6

sugar molecules that are bound to the ends of a DNA fragment.

Biology 204

Enzymes called ________ form breaks in DNA molecules to prevent 
overtwisting in the DNA helix during replication.
a.

topoisomerases

b. single­strand binding proteins
c.

DNA polymerases

d. RNA polymerases
e.

DNA ligases

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

Crossing over occurs in which phase of mitosis?
a.

metaphase

b. anaphase
c.

prophase

d. telophase
e.

none of the above

Genes that encode proteins that are always needed are called
a.

repressible genes.

b. promoter genes.
c.

constitutive genes.

d. inducible genes.
e.

operons.

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.

Principles of Biology I

a complex of a ribosome with its two subunits and several mRNAs.

7

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.

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.

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.

W­X­V­U

b. U­X­V­W
c.

X­W­U­V

d. V­U­W­X
e.

none of the above

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.

Which of the following represents the sequence of events during mitosis?
a.

8

prophase ? metaphase ? anaphase ? telophase

Biology 204

b. interphase ? metaphase ? anaphase ? telophase
c.

anaphase ? telophase ? metaphase ? interphase

d. interphase ? prophase ? anaphase ? metaphase
e.

metaphase ? telophase ? anaphase ? prophase

Random segregation refers to
a.

crossing over.

b. regulation of mitosis.
c.

events during transduction.

d. Barr bodies.
e.

paternal and maternal chromosomes.

Where is the amino­acid 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

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.

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 m­RNA.

— End of Assignment 2B —

Principles of Biology I

9