Biochemistry/Biochemistry MCQS PAPER SET 13 Sample Test,Sample questions

Question:
 
DNAs when charged, migrate in a gel towards the

1.positive pole

2.negative pole

3.will not migrate

4.none of these


Question:
 
In a typical electrophoresis experiment, larger fragments of DNA move more

1.slowly, so they appear nearer the top of a gel photograph

2.quickly, so they appear nearer the top of a gel photograph

3.slowly, so they appear nearer the bottom of a gel photograph

4. quickly, so they appear nearer the bottom of a gel photograph


Question:
 
Klenow fragment without free nucleotides exhibits

1.exonuclease activity

2.endonuclease activity

3. nickase activity

4.no activity


Question:
 
Without telomerase, what would happen to the ends of chromosomes after each round of replication?

1.Chromosomes would become progressively shorter

2.Nothing would happen

3.Chromosomes would get longer

4.none of the above


Question:
  
DNA gyrase in E. coli

1.adds positive supercoils to chromosomal DNA

2.can be inhibited with antibiotics

3.is required only at the oriC site

4.performs the same function as helicase in eukaryotes


Question:
  
DNA polymerases I also has

1.5'-3' exonuclease activity

2. 3'-5'exonuclease activity

3.both (a) and (b)

4.5'-3' endonuclease activity


Question:
  
Enzyme, responsible for proofreading base pairing is

1.DNA polymerase

2.Telomerase

3.Primase

4.DNA ligase


Question:
  
If one cell has AT contents 40%, what will be the percentage of Guanine residue?

1.60%

2.15%

3.30%

4.Guanine residue can not be calculated


Question:
  
One hypothesis of DNA replication suggested that the parental DNA molecules are broken into fragments. Both strands of DNA in each of the daughter molecules are made up of an assortment of parental and new DNA. This statement refers to which hypothesis?

1.Conservative theory

2.Dispersive theory

3.Semi-conservative theory

4. Evolutionary theory


Question:
  
What bands will be observed in a cesium chloride gradient after two rounds of replication?

1.One light, one medium and one heavy band

2.One light and one medium band

3.One medium band

4.One medium and one heavy band


Question:
30 nm wide helix with five or six nucleosomes per helix is known as

1.solenoid

2.halonoid

3.kinoplast

4.none of these


Question:
A cesium chloride will separate DNA molecules by

1.absorption

2.resorption

3.density

4.adhesion


Question:
After one replication in 15N, how many bands should be observed in a cesium chloride gradient?

1.One

2.Two

3.Three

4.A smear


Question:
Deoxyribonucleoside triphosphates, being need in the chain termination methods are

1.dATP

2.dGTP and dCTP

3.dTTP

4. all of these


Question:
DNA can be sequenced by the

1.chemical method

2.chain termination procedure

3.both (a) and (b)

4.physical method


Question:
DNA helicase is used to

1. unwind the double helix

2.interact the double helix closely

3.break a phosphodiester bond in DNA strand

4. none of the above


Question:
DNA replication takes place in which direction?

1.3' to 5'

2. 5 'to 3'

3.Randomly

4.Vary from organism to organism


Question:
E.coli DNA polymerases II and III lack

1.5' → 3' exonuclease activity

2.5' → 3' endonuclease activity

3. partially 5' → 3' exonuclease activity

4.partially 5' → 3' endonuclease activity


Question:
Each replication bubbles consists of

1. 3 replication forks

2. 2 replication forks

3. 4 replication forks

4. 1 replication forks


Question:
Enzymes, responsible for unraveling short segments of DNA is

1.DNA polymerase

2.helicase

3.DNA ligase

4.Primase


Question:
he most common liquid volumes in molecular biology are measured in

1.ml

2.μl

3.nl

4.1


Question:
In a cesium chloride gradient, DNA labeled with 15N and centrifuged will form a band

1.above DNA containing 14N

2. below DNA containing 14N

3. with 14N-containing DNA

4.all of these


Question:
In DNA double helix, the two DNA chains are held together by

1. covalent bonds between the pair of bases

2.hydrogen bonds between the pair of bases

3.ionic bonds between the pair of bases

4. none of the above


Question:
In DNA, guanine pairs with

1.Adenine

2.Cytosine

3.Thymine

4.Uracil


Question:
In DNA, there are

1.five bases known as adenine, guanine, thymine, tryptophan and cytosine

2.four bases known as adenine, guanine, thymine and cytosine

3.three bases known as adenine, guanine and cytosine

4.only two bases known as adenine and cytosine


Question:
In sperm heads, DNA is particularly highly condensed and the histones are replaced with small basic protein called

1.protamines

2.purines

3.pyrimidines

4. all of the above


Question:
In the study of one experiment it was found that the value of Tm for DNA is = 40° C. If the cell has 20% GC at the above Tm, then what will be value of 'Tm' if the GC% increases to 60%?

1.Remains same

2.Increases

3.Decreases

4.Can not be compared


Question:
The chromosomal DNA complexes with

1.three types of histone as H1, H2A and H4

2.five types of histone as H1, H2A, H2B, H3 and H4

3.four types of histone as H1, H2A, H3 and H4

4.two types of histone as H1 and H4


Question:
Messelsen and Stahl model of replication was called

1.conservative replication

2.semi-conservative replication

3.dispersive replication

4. Cri du Chat


Question:
n DNA replication, one new strand is synthesized complementary to an old (parent) strand and is referred as

1.mutational

2.semiconservative

3.discontinuous

4.antiparallel


Question:
Nucleosome is

1.an octamer of four histones with H1 protein

2.an hexamer of three histones with H1 protein

3.an hexamer of three histones without H1 protein

4.an octamer of four histones without H1 protein


Question:
Okazaki fragments occur during

1.transformation

2.replication

3.polymerase reaction

4.synthesis


Question:
Proteins involved in opening a replication bubble are

1.DNA helicases

2.single stranded binding proteins

3.ligase

4.DNA topoisomerase


Question:
Reverse transcriptase produces

1.DNA from peptides

2.RNA from DNA

3.RNA from RNA

4.DNA from RNA


Question:
Taylor, Woods and Hughes labeled Vicia DNA by allowing new DNA synthesis in the presence of radioactive thymine. After DNA replication (S phase of the cell cycle), it was observed that

1. only one chromatid of a chromosome was labeled

2.both chromatids of a chromosome were labeled

3. both (a) and (b)

4.neither chromatid was labeled


Question:
The 5' and 3' numbers are related to the

1. length of the DNA strand

2.carbon number in sugar

3.the number of phosphates

4.the base pair rule


Question:
The DNA polymerase in bacteria, responsible for DNA synthesis is

1.Polymerase I

2.Polymerase II

3.Polymerase III

4.all of these


Question:
The higher order structure of DNA shows symmetry, whereas the higher order structures of most proteins do not. Why isn't protein shape more regular like DNA?

1. DNA has one main function in cells whereas proteins have many.

2.The many different amino acid R groups on proteins confer many different shapes.

3.Some S amino acids cause proteins to bend; others cause protein to flatten.

4.All of the above


Question:
The melting of 40-45 bp at the oriC site of E. coli requires

1.DNA + ATP + HU

2.DNA + ATP + HU + DNAb

3. DNA+ ATP + HU + DNAb + DNAa

4.DNA + ATP + HU + DNAb + DNAa + Pol III holoenzyme


Question:
The nicks or gaps between Okazaki fragments are eventually sealed by

1.gyrase

2.DNA ligase

3.RNA ligase

4. polymerase


Question:
The nucleosome consists of histone

1.octamer and 146 bp of DNA

2.tetramer and 146 bp of DNA

3.hexamer and 146 bp of DNA

4.none of the above


Question:
The overall conclusion of the Hershey-Chase experiment was that

1.DNA was responsible for heredity

2.proteins and DNA were responsible for heredity

3.the ratio of Adenine to thymine was always the same

4.phage DNA was similar to bacterial DNA


Question:
The packing ratio of nucleosomes is about

1.6

2.8

3.7

4.9


Question:
The rapid appearance of HIV-1 strains that are resistant to AIDS drugs is due in part to which of the following property of its reverse transcriptase?

1.AZT (zidovudine) is too expensive to be taken in effective doses

2.The RNase H domain of p66 causes error prone synthesis

3. It lacks a proofreading exonuclease

4.It has low affinity for the correct dNTP's


Question:
The replication of a linear DNA molecule in a eukaryotic chromosome creates a problem which is reported to be sorted out by

1.using enzyme called telomerase

2.shortening of the double stranded replicated portion

3.using RNA as a template

4.none of the above


Question:
The role of primase is to

1.dismantle RNA primer

2.cleave and unwinds short sections of DNA ahead of the replication fork

3.proofread base pairing

4. synthesize an RNA primer to begin the elongation process


Question:
What is the approximate percentage of repetitive DNA sequences in human DNA?

1. 10 to 20%

2. 20 to 30%

3. 30 to 40%

4. 40 to 50%


Question:
What is the approximate size (in kb) of the E. coli genome?

1.3000 kilobase

2.45000 kilobase

3.55000 kilobase

4.65000 kilobase


Question:
What is the main damaging effect of UV radiation on DNA?

1.Depurination

2.Formation of thymine dimers

3.Single strand break

4.Dehydration


Question:
What is the only common methylation in the DNA of eukaryotes?

1.Adenosine in GpA dinucleotides

2.Guanosine in ApGpA trinucleotides

3.Cytosine in CpG dinucleotides

4.None of the above


Question:
What is the range of melting point temperatures (Tm) for most DNA molecules?

1. 50 to 60°C

2.60 to 80°C

3. 70 to 90°C

4. 80 to 100°C


Question:
Which DNA polymerase removes RNA primers in DNA synthesis?

1.Polymerase I

2.Polymerase II

3.Polymerase III

4.none of these


Question:
Which of the following enzyme adds complementary bases during replication?

1.Helicase

2.Synthesase

3.Replicase

4.Polymerase


Question:
Which of the following is incorrect?

1.In DNA double helix, two strands of the DNA are bound with each other with the bases

2.Adenine always pairs with thymine

3.Guanine always pairs with the cytosine

4.None of the above


Question:
Which of the following is used to determine the appropriate stringency (Wallace rule)?

1.Tm = 2 x (No.of G:C base pair) + 4 x (No.of A:T base pair)

2.Tm = 4 x (No.of A:T base pair) + 2 x (No.of G:C base pair)

3. Tm = 4 x (No.of G:C base pair) + 2 x (No.of A:T base pair)

4. Tm = 69.3° + 0.41 (%)G+C -650/1


Question:
Which of the following would not contain DNA?

1.Yeast

2.Bacteria

3.Glass crystals

4.Mold


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