Tag: biology

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

Exon segments are reunited after splicing by

  1. RNA primase

  2. DNA polymerase

  3. RNA polymerase

  4. RNA ligase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
RNA primase synthesizes RNA primer which is a stranded segment (complementary to the template) and has a free 3’ hydroxyl group to facilitate the 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 the 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. The correct answer is D.
Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Which is true for DNA helicases?

  1. Separate DNA strands and establish replication forks

  2. ATP requiring unwinding enzymes

  3. Hydrolyse ATP

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During DNA replication, two hexamers of helicases are loaded onto each DNA strand. Helicases move along the double stranded DNA and separate the strands by breaking hydrogen bonds between base pairs. ATP hydrolysis provides the required energy for breaking of hydrogen bonds; options B and C are correct. Thereby, DNA is unwound bidirectionally and two potential replication forks are created. The point at which two DNA strands are separated to facilitate the replication is called replication fork; option A is correct. Correct answer is D.

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

How many types of RNA polymerases are operative in eukaryotes?

  1. Four

  2. Three

  3. Two

  4. One
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Eukaryotes have three RNA polymerases which are structurally distinct complexes, though share certain subunits in common, and have a specific function and specific promoter sequence. RNA polymerase I synthesize preribosomal RNA (pre-rRNA), which contains the precursor for the 18S, 5.8S, and 28S rRNAs. RNA polymerase II is synthesized mRNAs and some specialized RNAs. RNA polymerase III makes tRNAs, the 5S rRNA, and some other small specialized RNAs. Option B is correct.

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

Which of the enzyme joins the broken strands of DNA?

  1. Nuclease

  2. Kinase

  3. Ligase

  4. Endonuclease
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Two classes of enzymes are most important in generating recombinant DNA molecule. First, restriction endonucleases (also called restriction enzymes) recognize and cleave DNA at specific DNA sequences (recognition sequences or restriction sites) to generate a set of smaller fragments. Second, the DNA fragment to be cloned can be joined to a suitable cloning vector by using DNA ligases to link the DNA molecules together. DNA ligase catalyzes the formation of new phosphodiester bonds in a reaction that uses ATP or a similar cofactor.

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

Which of the following does not describe a correct function of DNA polymerase?

  1. It helps to replace RNA primers with DNA nucleotides.

  2. It adds complementary DNA base pairs in a 5 to 3 direction along the DNA leading and lagging strands.

  3. It proofreads the replicated DNA and replaces mismatched DNA nucleotides.

  4. It adds RNA nucleotides along the DNA template in transcription.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

DNA polymerase is an enzyme used in the replication of DNA. It ads the DNA primers to the parent chain. This enzyme acts in the 5'-3 direction and thus forms lading stand on the chain that has 3'5' direction.

There are 3 DNA polymerases in use from which only the DNA polymerase II helps in replication and rest of the two are used in the DNA proofreading.

So, the correct option is 'It adds RNA nucleotides along the DNA template in transcription.'

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

DNA replication requires

  1. DNA polymerase

  2. DNA ligase

  3. RNA polymerase

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

RNA polymerase serves as primase during DNA replication and synthesizes RNA/DNA primer which is a stranded segment (complementary to the template) and has a free 3’ hydroxyl group to facilitate the addition of deoxyribonucleotides by DNA polymerase enzyme. DNA polymerase is polymerizing enzyme that has 5’ to 3’ polymerization and 3’ to 5’ exonuclease proofreading activities; it adds deoxyribonucleotides to free 3’ hydroxyl group of primer to synthesize new DNA strands. DNA ligase enzyme joins two Okazaki fragments together via phosphodiester bond between 3' hydroxyl at the end of one fragment and a 5' phosphate at the end of another fragment. Thus, option D is the correct answer. 

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

The helicase enzyme breaks

I. Covalent bonds

II. Hydrogen bonds

III. Ionic bonds

  1. II only

  2. I and II

  3. I and III

  4. II and III

  5. I, II and III
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
 Helicase is the enzyme that binds to DNA and remodels the nucleic acid i.e DNA. During DNA replication, the double helix unwinds as the preliminary step. The unwinding of DNA strand is catalysed by helicase enzyme. DNA polymerase is the enzyme responsible for the ongoing of the replication process, which was initiated by RNA primer. It breaks the hydrogen bonds between the nucleotides and thus helps in unzipping the DNA strands. Thus, the correct answer is option A.
Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

DNA ligase helps in                           

  1. Joining bits of DNA

  2. Splitting or separation of two strands of DNA

  3. Renaturation

  4. Denaturation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In molecular biology, DNA ligase is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

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

DNA polymerase enzyme is required for the synthesis of 

  1. RNA from DNA

  2. DNA from DNA

  3. RNA from RNA

  4. DNA from RNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA polymerase is an enzyme that synthesizes DNA molecules from deoxynucleotides, the building blocks of DNA. It helps in DNA replication (DNA dependent DNA synthesis). This enzyme works in pairs to create two complementary DNA strands from a single original DNA molecule.

RNA from DNA (transcription) is synthesized by RNA polymerase.
DNA from RNA is synthesized by reverse transcriptase enzyme in some viruses.
So, the correct option is 'DNA from DNA'.

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

The area of unwinding and separation of DNA strands during replication is called

  1. Origin

  2. Initiation point

  3. Primer

  4. Replication fork
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Y-shaped region where DNA strands unwind and separate to undergo replication is known as the replication fork. The origin is where replication begins, and primers are short RNA sequences needed to start synthesis.