Tag: biology

Questions Related to biology

In bacterial DNA replication, synthesis starting from the site of origin of replication

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

  1. Involves RNA primers

  2. Requires telomerase

  3. Proceeds unidirectionally

  4. Moves bidirectionally

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Correct Option: D

Consider the following statements and choose the correct option.

In eukaryotes
(i) RNA polymerase I transcribes rRNA.
(ii) RNA polymerase I transcribes snRNA.
(iii) RNA polymerases II transcribes tRNA.
(iv) RNA polymerase II transcribes hnRNA.

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

  1. 1 and 2 are correct.

  2. 1 and 3 are correct.

  3. 1, 2 and 4 are correct.

  4. 2 and 3 are correct.

  5. 1 and 4 are correct.

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Correct Option: E
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 transcribes the presursor of mRNA which is heterogenous RNA (hnRNA). 
RNA polymerase III makes tRNAs, the 5S rRNA, and sNRNAs. 
Therefore, the correct answer is option (E).

Choose the correct answer from the alternatives given.
A restriction enzyme breaks bonds between the

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

  1. base pairs of a DNA molecule

  2. sugar and phosphate components of a nucleic acid molecule

  3. base pairs of a DNA-RNA hybrid molecule.

  4. exons and introns of a DNA molecule

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Correct Option: B
Explanation:

Restriction enzymes are the enzymes that have the capability to cleave the phosphodiester bonds between the sugar molecule and the phosphate molecule. It has a property of cleaving DNA molecules at or near a specific sequence of bases. This is produced by certain strains of bacteria. Each restriction enzyme cleaves around a specific DNA sequence. Example: EcoR1 splices around sequence GAATTC, BamH1 cleaves around GGATCC, etc.

So, the correct option is 'sugar and phosphate components of a nucleic acid molecule'.

Replication of DNA on its lagging strand is initiated by.

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

  1. DNA polymerase III

  2. RNA primer

  3. DNA polymerase I

  4. DNA ligase

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Correct Option: A

Choose the correct answers from the alternatives given :
Which enzyme catalyzes the synthesis of a new strand for a DNA molecule by linking nucleotides to the developing strand?

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

  1. DNA ligase

  2. DNA polymerase

  3. Single-strand binding proteins

  4. Topoisomerase

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Correct Option: B
Explanation:

DNA polymerase is an enzyme that synthesis DNA molecules from deoxyribonucleotides which are the building blocks of DNA. Each nucleotide contains a sugar molecule (deoxyribose sugar), a phosphate molecule, and any one of the nucleotides (adenine, guanine, cytosine and thymine). They basically help in DNA replication by working in pairs to form a new DNA molecule. 

So, the correct option is 'DNA polymerase'.

A bacterium with completely non-radioactive DNA was allowed to replicate in radioactive medium for three generation what $ \%$ of the bacteria should contain radioactive DNA:

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

  1. $ 25\%$

  2. $ 75\%$

  3. $ 0\%$

  4. $ 100\%$

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Correct Option: B

Choose the correct answers from the alternatives given :
In DNA replication, the Okazaki fragments on the lagging strand are joined together by

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

  1. DNA ligase

  2. DNA polymerase

  3. Primase

  4. Helicase

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Correct Option: A
Explanation:

DNA ligase is an enzyme that facilitates the joining of the strands of the DNA by assisting the formation of phosphodiester bonds between two nucleotides.

DNA polymerase is an enzyme that helps in DNA replication by the formation of deoxyribonucleotides, building blocks of DNA.
Primase is an enzyme that synthesis short RNA sequences called primers that help in the initiation of DNA synthesis.
Helicase is an enzyme that helps in winding and unwinding of the double-stranded structure of the DNA.
So, the correct option is 'DNA ligase'

During replication, DNA gyrases takes part in 

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

  1. Nicking DNA in eucaryotes

  2. Nicking DNA in procaryotes

  3. Synthesis of prier in eucaryotes

  4. Synthesis of primer in procaryotes

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Correct Option: A

Which enzyme catalyses the synthesis of a new strand for a DNA molecule by linking nucleotides to the developing strand?

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

  1. RNA polymerase

  2. DNA ligase

  3. DNA polymerase

  4. Topoisomerase

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Correct Option: C
Explanation:

  • RNA polymerase helps in DNA dependent RNA synthesis. This process is known as transcription. DNA strands are used as a template to synthesize RNA molecules.
  • DNA ligase is used to join DNA segments during DNA repair or during replication (to join Okazaki fragments of the lagging strands).
  • DNA polymerase works in the pair to synthesis new strand for DNA molecule from deoxyribonucleotides. In other words, it helps in DNA dependent DNA synthesis.
  • Topoisomerase enzyme participates in overwinding or unwinding of DNA. During DNA replication or transcription, DNA becomes overwound ahead of the replication fork. It binds to DNA and cut the phosphate backbone of either one or both the DNA strands.
So, the correct option is 'DNA polymerase'.

Thermostable enzymes Taq and Pfu isolated from thermophilic bacteria are

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

  1. DNA polymerases

  2. DNA ligases

  3. Restriction endonucleases

  4. RNA polymerases

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Correct Option: A
Explanation:

Thermophilic bacteria that live in hot springs and hydrothermal vents. Taq polymerase and Pfu polymerase are enzymes isolated from thermophilic bacteria. These enzymes are used in polymerase chain reaction as these enzymes are able to withstand the protein-denaturing conditions (high temperature) required during polymerase chain reaction ( PCR ). 

So, the correct option is 'DNA polymerases'.