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Questions Related to biology

Deoxyribonucleoside triphosphates serve dual purposes in DNA replication. In addition to acting as substrate, the other function is similar to?

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. DNA polymerase

  2. rRNA

  3. Topoisomerase

  4. ATP

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Correct Option: D
Explanation:
Answer :
i) The Deoxyribonucleoside Triposphate act as both energy (ATP) and substrate for the polymerization reaction.
ii) The Deoxyribonucleoside Triposohate (DTPs) is considered as the building block of DNA synthesis.
iii) The DTPs possess two high-energy phosphate that has the ability to provide energy to the replication by breaking their molecules.  
iv) It serves as a substrate that is consumed during the enzymatic reaction of replication.
So correct answer is option D.ATP.

DNA replication includes which of the following enzymes?

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. DNA ligase

  2. DNA polymerase and ligase

  3. RNA polymerase and ligase

  4. All of the above

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Correct Option: D
Explanation:

DNA polymerase and ligase as well as RNA polymerase and ligase have an important role in DNA replication. DNA replication, like all biological polymerization processes, proceeds in three enzymatically catalyzed and coordinated steps : initiation, elongation and termination. All enzymes mentioned play important roles in these steps of replication.

Which of the following is true about DNA polymerase?

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. It can synthesize DNA in the 5' to 3' direction

  2. It can synthesize DNA in the 3' to 5' direction

  3. It can synthesize DNA in both directions

  4. Depend upon the condition

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Correct Option: A

Select the correct statement:

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. DNA polymerase has high degree of accuracy

  2. During DNA replication, only one strand of DNA act as template for synthesis of new strand.

  3. Taylor has proved by his experiment that DNA is the genetic material

  4. E. coli has $4.6 \times 10^9$ bp in its genetic material

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Correct Option: A

Which of the following enzyme is used in DNA multiplication?

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. RNA polymerase

  2. DNA endonuclease

  3. Exonuclease

  4. DNA polymerase

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Correct Option: D
Explanation:

The DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA. These enzymes are essential to DNA replication and usually work in pairs to create two identical DNA strands from a single original DNA molecule. During this process, DNA polymerase reads the existing DNA strands to create two new strands that match the existing ones. Every time a cell divides, DNA polymerase is required to help duplicate the cells DNA, so that a copy of the original DNA molecule can be passed to each of the daughter cells. In this way, genetic information is transmitted from generation to generation.

DNA polymerase is needed for

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. Replication of DNA

  2. Synthesis of DNA

  3. Elongation of DNA

  4. All of the above

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Correct Option: D

Enzyme responsible for DNA chain elongation is

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. DNA polymerase II

  2. DNA ligase

  3. RNA poymerase III

  4. DNA polymerase III

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Correct Option: D
Explanation:
DNA polymerase II has 5’ to 3’ polymerization activity and 3’ to 5’ exonuclease activity and is mainly involved in DNA repair which makes option A incorrect. DNA polymerase III is a heteroenzyme with 10 subunits and has both 5’ to 3’ polymerization and 3’ to 5’ exonuclease activity. The gamma and epsilon subunits impart processivity, the ability to remain on the template and not to dissociate and reassociate, which in turn allow it to carry out primer elongation which makes option D correct. DNA ligase enzyme joins two DNA fragments together via phosphodiester bond between 3’ hydroxyl at the end of one fragment and a 5’ phosphate at the end of another fragment; it does not polymerise DNA which makes option B incorrect. RNA polymerase III synthesizes tRNAs, the 5S rRNA, and some other small specialized RNAs which makes option C incorrect.

DNA helicase helps in 

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. Opening supercoils of DNA

  2. Making DNA helix

  3. Opening two chains of DNA helix

  4. Making hydrogen bonds of nitrogenous bases

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Correct Option: C
Explanation:

Helicases move along the double-stranded DNA and separate the strands by breaking hydrogen bonds at the expense of energy from ATP. DNA unwinding by helicases creates topological stress/supercoils in the helical DNA structure which is relieved by the action of topoisomerases. These enzymes transiently break both DNA strands of one chromosome thereby making the other chromosome to pass through the break and relieve the stress. DNA polymerase enzyme synthesizes DNA strands by adding deoxyribonucleotides to 3' end of the primer via phosphodiester bonds; it uses parental DNA as template. Hydrogen bonding between base pairs is facilitated by the presence of hydrogen bond donor (primary and secondary amine groups or hydroxyl groups) and complementary hydrogen bond acceptor (carbonyls and tertiary amines) in bases; it is not enzymatic process. The correct option is C.

Which of the following help in repairing of DNA?

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. Ligase

  2. DNA polymerase I

  3. RNA primer

  4. DNA polymerase III

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Correct Option: B
Explanation:

DNA polymerase I serve clean-up functions during replication, recombination, and repair. It has 3' --> 5' proofreading exonuclease activity and 5' --> 3' exonuclease activity. The 5' --> 3' exonuclease activity of DNA polymerase I can replace an error containing the segment of DNA/RNA, paired to the template strand which is then simultaneously replaced by polymerase activity of the same enzyme. The process is called as nick translation. DNA polymerase III with its ten types of subunits has 5' --> 3' polymerization and 3' --> 5' proofreading activities in its $\alpha$ and $\epsilon$ subunits, respectively. 

As DNA pol III does not have 5' --> 3' exonuclease activity; it can not remove the erroneous segments of DNA/RNA. RNA primer is an oligonucleotide, synthesized by primase enzyme, that is elongated into long strands of deoxyribonucleotides or ribonucleotides by DNA and RNA polymerase enzymes respectively. Ligase enzyme joins two DNA strands by facilitating phosphodiester bond formation between the adjacent nucleotides; it can not cut and remove the DNA segments and thus, can not repair DNA. The correct option is B.

During splicing, the exons are joined and the enzyme which catalyzes this reaction is 

dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

  1. RNA ligase

  2. RNA catalase

  3. RNA polymerase

  4. RNA primase

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Correct Option: A
Explanation:
RNA primase synthesizes RNA primer which is a strand segment (complementary to the template) and has a free 3’ hydroxyl group to facilitate addition of nucleotides by polymerase enzymes. RNA polymerase synthesizes RNA using DNA template strand by adding the ribonucleotides to a primer in 5' to 3' direction via phosphodiester bonds. Splicing is removal of introns from the primary transcript and ligation of exons to form a continuous sequence specifying a functional polypeptide. RNA ligase enzyme joins two exons together via phosphodiester bond between 3’ hydroxyl at the end of one exon and a 5’ phosphate at the end of another exon.