TEST 3 SBI4U MOLECULAR GENETICS
Student’s Name
Knowledge /
Understanding
12
:
Andrew
Date:
Thinking/Inquiry
Communication
Application
Marks
12
10
12
46
Identify the choice that best completes the statement or answers the question
( K= 8).
1. Which enzymes are responsible for most DNA repair? D
a. DNA polymerase I and II
b. DNA polymerase II and III
c. DNA polymerase I and III
d. DNA ligase
2. Which structure can aid in gene regulation? D
a. histones
b. nucleosomes
c. solenoids
d. all of the above
3. The process by which mRNA is turned into a protein sequence is called D
a. elongation
b. initiation
c. transcription
d. translation
4. What happens when telomeres become too short? B
a. coding regions of DNA are lost
b. cell division stops immediately
c. new telomeres are formed
d. the cell begins to divide uncontrollably
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5. What does the base sequence AAU GGC code for? A
a. one specific amino acid, followed by a nonsense codon
b. two enzymes
c. two specific amino acids
d. one enzyme and one specific amino acid
6. Which type of information can an aminocentesis test determined? D
a. if either of parents of a child have chromosomal abnormalities
b. if germ- line therapy should be performed before conception
c. if a man and a woman have chromosomal abnormalities that would prevent conception
d. if a fetus has chromosomal abnormalities
7. Telomeres are absent in prokaryotes because B
a. prokaryotes are single celled and cannot age
b. the circular chromosomes in prokaryotes has no end
c. plasmids have the same function in prokaryotes
d. prokaryotes lack telomerase
8. Prokaryotes use which of the following DNA polymerase enzymes? D
a. DNA polymerase I
b. DNA polymerase III
c. DNA polymerase II
d. all of the DNA polymerase
enzymes
9. Which nitrogenous base is shown here? D
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a. adenine
b. thymine
c. guanine
d. cytosine
10. Which statement about a bacteriophage is true? C
a. bacteria can only live in the presence of oxygen
b. it is a bacterium that feeds on virus
c. it is a virus that infects bacteria
d. bacteria does not require the presence of oxygen
11. In a given double strand DNA sequence 14% is guanine. Calculate the percentage of the
other three bases. ( K=2)
36% A
36% T
14% C
14% G
12. Match each structure to the type of bond it contains or its function. Answer choices may be
used only once : (T/I=6)
i. Phospho diester bond
a. between the phosphate of one nucleotide and the
deoxyribose sugar of the next nucleotide.
ii. two hydrogen bonds
b. the enzyme helicase
iii. three hydrogen bonds
c. deoxyribose sugar and thymine
iv. carbon 1 to nitrogen bond
d. base pair mismatch
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v. breaks hydrogen bond
e. between the nitrogenous bases adenine and thymine
vi. T-G bond
f. between the nitrogenous bases cytosine and guanine.
I
ii
iii
iv
v
vi
a
e
F
c
b
d
13. Indicate whether the following statements are true or false.( I=4)
i. The central dogma outlines the flow of information from DNA to tRNA to protein. T
ii. More than one ribosome can translate an mRNA molecule at a time. T
iii. Cancer cells have very few telomerase. T
iv. During DNA replication, base pairs are always complementary.F
14. Name the enzymes involved in DNA replication and mention their functions.( I= 3)
Helicase: Undiwnds dna double helix
Gyrase: Relieves the buildup of torque while unwinding
Primase: Lays diwn RNA primers
DNA polymerase III: Main DNA synthesis enzyme
DNA polymerase I: replaces RNA primers with dna
Ligase: Fills in the gaps
Telomerase: Extends telomeres
Nuclease: Removes defectives sections of nucleotides
15. Complete the following statements.( T/I=2)
i. The special protein that forms the central core of a chromosome is histone
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ii. A (n) telomere prevents the loss of genes from the ends of chromosomes during replication.
16. Explain the various steps involved in PCR.( Comm 4)
1. Denaturation: Breaking two strands of DNA apart by heating, causes h bonds to weaken
2. Aneealing: Primer binds to target dna sequence and initiates polymerization.
3. Extension: New strands of DNA are made using original strands as template
17. Use the picture of a DNA nucleotide to identify the labelled parts A,B,C and D. ( Comm.4)
.
A: Nitrogenous base
B:Sugar phosphate backbone
C: Sugar
D: Phosphate group
20. Discuss the relationship between replication and aging. ( Comm.2)
Aging and replication go hand in hand because the methods which our bodies use to replicate
are directly related to the signs of aging in our bodies. For example, as we get older and our
telomeres shorten, we know that our risk of cancer increases. This is because of the overhang
that is left at the end of DNA replication.
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21. Distinguish between spontaneous mutation and induced mutation.( App 2)
Spontaneous mutations happen spontaneously during DNA replication. Induced mutations are
caused by mutagens.
22. Why do we need a different flu vaccine every year. ( App 2)
The reason that we need a different flu vaccine every year is because every flu season, there
are different viruses circulating. Since the flu virus adapts rapidly, it is crucial to get a new shot
every year.
23. Explain what happens to cells to cause them to become cancerous.( App 2)
When a cell is no longer able to stop itself from dividing. If a cell loses the ability to stop
reproducing, This usually happens after several mutations cause a cell to lose control of its life
cycle and ultimately leads to the cell not being able to commence apoptosis.
24. A short fragment of a particular gene includes the following sequences of nucleotides.
3’ TACTACGGTAGGTATA-5’
Write out the mRNA sequence.
( App 2)
5’-AUGAUGCCAUCCAUAU-3’
25. Summarize the different steps involved in all stages of translation.( App 4)
1. Initiation: small subunit attaches to 5 end and looks for start codon (AUG), then recruits large
ribosomal subunit and tRNA
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2. Elongation: Ribosome travels along mRNA and reads codons. Grabs trna and matches
anticodons with codons. Amino acids are joined together by peptide bonds and trna leaves.
Creates A. A. string outside of ribosome.
3. Termination. When ribosome reaches stop codon, a release factor will bind to stop codon
and cause amino acid chain to be released, ribosome subunits separate.
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