mcq in genetics & dna

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1.
The following are true about DNA synthesis:
a. it requires DNA
polymerase
b.
reverse transcriptase enzymes are involved
c.
moves in a 5'---> 3' direction
d. the
rate of error in DNA synthesis is 1 in 105 base pairs
e.
cytarabine inhibits DNA synthesis

Answera.T b.F c.T
d.F e.TThe rate of error is 1 in 109 base pairsCytarabine inhibits
DNA polymeraseand therefore DNA synthesis.

2. With regard to DNA
molecules:
a. they contain
adenine, cytosine, guanine and uracil bases
b. they
can be detected with Western blotting
c. they
can be detected with Southern blotting
d. they
are denatured at temperature of 1000C
e. they
are denatured by pH of £ 7.14

Answera.F b.F c.T
d.T e.TDNA contains thymidine instead of uracil.Western blotting is
used to detect proteinSouthern blotting for DNA detectionNorthern
blotting for RNA detection

3. G-proteins:
a. are activated by
the binding of an extracellular ligand to a membrane receptor
b. can
be mutated in tumour cells
c.
mediate the action of glucocorticoid hormone
d. they
are inactivated by cholera toxins.
e. bind
to DNA to regulate gene transcription

Answera.T b.T c.F
d.F e.FSteroid hormones act without involving the G-proteins.Cholera
toxins inhibit the inactivation of G-proteinscausing elevation of cAMP
and the intestinalepithelial cell to secretes ions uncontrollably.The
actions of G-proteins are confined to the cellmembrane

4. The following is
true about gluconeogenesis:
a. it occurs in liver
b. it
occurs in kidney
c. it
occurs in adipose tissue
d. it
is inhibited by glucagon
e. it
is stimulated by insulin

Answera.T b.T c.F
d.F e.FAdipose tissue does not undergo gluconeogenesis.The process
is stimulated by glucagon and inhibitedby insulin

5.
DNA:
a. is found in herpes
virus
b. is found in the
nucleosomes
c. is found outside
the cell nucleus
d. is replicated in
the S phase of the cell cycle
e. duplicates
simultaneously in all chromosomes

Answera.T b.T c.T
d.T e.FNucleosome beads occur where DNA is woundaround four pairs of
histone molecules.It is found in the mitochondria.DNA in
heterochromatic duplicates late.

6.
Heterochromatin:
a. contains a highly
repetitive sequence of DNA
b. is the inert
segment of the chromosome adjacent
to the centromere
c. may be lost
without harmful effect in Robertsonian
translocation
d. is tightly coiled
during the interphase
e. makes up the p arm
of the acrocentric chromosomes

Answera.T b.T c.T
d.T e.T

7.
Increase number of chromosomes occur in:
a. Turner's syndrome
b. fragile-X syndrome

c. Down's syndrome
d. Klinefelter's
syndrome
e. Retinoblastoma

Answera.F b.F c.T
d.T e.FTurner's syndrome is one chromosome short.The number is normal
for fragile-X syndromeand retinoblastoma.

8. The
following are true:
a. mRNA can be
detected with Southern blotting
b. DNA can be
detected with Northern blotting
c. restriction
endonucleases cut the DNA into
lengths of about 20 nucleotide base sequences
d. restriction
fragment length polymorphism occurs
mainly in the coding region of the DNA
e. polymerase chain
reaction requires the use of
DNA polymerase

Answera.F b.F c.F
d.F e.TSouthern blotting is used to detect DNA whereasNorthern
blotting for mRNA. Restriction endonucleasescut the DNA into lengths of 4
to 6 nucleotide basesequences.Restriction fragment length polymorphism
(RFLP) aredue to intron polymorphisms. Introns are sections of DNAthat
will be spliced out after transcription, but beforethe RNA is used.

9. The polymerase chain
reaction:
a. produces multiple
copies of DNA
b. requires
oligonucleotide primers
c. has a high
specificity but low sensitivity
d. requires the use
of heat
e. can be used to
detect RNA virus
Answera.T b.T c.F
d.T e.TPCR is highly sensitive and therefore it is essentialthat the
specimen contains no contaminant.Contaminant with even a single copy of
DNA may bedetectable. It can be used to detect RNAusing reverse
transcriptase.

10. With regard to
mitochondrial DNA:
a. it is
double-stranded
b. it mutates 10
times more frequently than nuclear DNA
c. each mitochondrion
contains about 100 DNA
molecules
d. it has no introns
e. Leber's congenital
amaurosis is caused by defective mitochondrial DNA
Answera.T b.T c.F
d.T e.FMitochondrial DNA has no introns and repairmechanisms.
Therefore, a mutation can easilycause a disturbance of the DNA
sequence.Each mitochondrion contains about 2 to 10 DNAmolecules.Leber's
optic neuropathy and not Leber's congenitalamaurosis is caused by
defective mitochondrialDNA.

11. The
following are true about nuclear DNAs:
a. about 50% of the
nuclear DNA codes for proteins
b. they are tightly
wrapped around histones to form
nucleoprotein complex
c. introns interrupt
the coding sequence
d. exons are removed
during splicing
e. the base pairings
are bound together by hydrogen
bonds
Answera.F b.T c.T
d.F e.TOnly 3% of nuclear DNA codes for protein. Introns
whichinterrupts the DNA sequence are removed duringsplicing. .
12. The HLA B27
molecule:
a. is class II major
histocompatibility antigen
b. is expressed
mainly in antigen presenting cells
c. occurs in 8% of
the general population
d. occurs in 90% of
patients with ankylosing spondylitis
e. is commoner in
patients with Yersinia arthritis
Answera.F b.F c.T
d.T e.THLA B27 molecule is class I HLA or majorhistocompatibility
antigens. Class II HLAantigens are found in antigen presenting cells.

13. The
following are true about mRNA:
a. only 1% of the
cellular RNA is mRNA
b. human mRNA is
monocistronic
c. introns are not
transcribed into mRNA
d. mutation of the
DNA sequence invariably gives rise to
a change in the amino acid sequence of the resulting
protein
e. RNA polymerase II
gives rise to protein encoding
mRNA
Answera.T b.T c.F
d.F e.THuman mRNA is monocistronic meaning each mRNAcodes for one
protein. Introns are transcribedand then spliced out of the RNA before
mRNA leavesthe nucleus. The same amino acid may be encoded bymultiple
codons. As a result, mutation of DNAsequence does not always give rise
to change inthe amino acid sequence.

14. With regard to
histones:
a. they are basic
proteins
b. they are essential
for the formation of stable DNA
c. mitochondria do
not contain histones
d. in the
chromosomes, the weight of the histones equal to that of the
DNA
e. the amino acid
composition of histones show great variability
amongst different human races
answera.T b.T c.T
d.T e.FHistones are basic protein which bind with DNA to
formchromosomes - a stable structure.They are absent in the
mitochondria.The amino acid composition of histones is highlyconserved
even between distantly related species.

15. In the regulation
of genes:

a. more than 90% of
the base sequences in human DNA have not
known function
b. extrons are the
part of the gene that code for amino acids found in
the final proteins.
c. introns usually
begins with the nucleotide sequence GT
d. splicing cut out
the mRNA coded by introns.
e. promoters are
responsible for initiating gene transcription
answera.T b.T c.T
d.F e.TIn the gene, the extrons represent the expressed sequenceof
the DNA whereas introns the interveningsequences. Introns usually begin
with the nucleotidesequence GT and end with AG.

16. Which of the following posttranslational
modifications represents formation of a covalent bond between the side
chains of two amino acid residues?

a.
Disulfide bond formation
b.
Hydroxylation
c.
Glycosylation
d.
Phosphorylation
e.
Lipid attachment
Ans:A
17. Zinc-finger motifs in proteins are frequently
associated with

a.
nucleotide binding.
b.
protein-protein interactions.
c. Ca2+
binding.
d. DNA
binding.
e.
membrane binding.
Ans:D

Exam on genetics
& DNA
http://www.tvdsb.on.ca/westmin/science/sbioac/genetics/genquiz.htm

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