Biology

Molecular Genetics

851 Questions

Molecular genetics explores the mechanisms of genetic information transfer, including DNA replication, transcription, and translation. It is a core component of biology syllabi. These concepts frequently appear in general science sections of major competitive exams.

DNA replicationTranscription processTranslation processRNA typesCentral dogma

Molecular Genetics Questions

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

The transforming substance in Griffith's experiment is 

  1. protein

  2. DNA

  3. mRNA

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

The transforming principle in Griffith's experiment is DNA. Griffith conducted an experiment in 1928. In this experiment he chose two strains of Stephylococcus pneumoniae bacteria. One of them was a smooth strain which was virulent and the other one was a rough strain which was non-virulent. The smooth strains caused pneumonia when they were injected to the mice, and the rough strains did not cause pneumonia in mice. Griffith heat killed the smooth strain bacteria and injected them into mice and he observed that pneumonia was not caused in them. He mixed the heat killed smooth strain and rough strain and injected the mixture into mice and this mixture caused pneumonia in mice. When he tested the blood of the mice, he saw both rough and smooth strains of bacteria. This implied that some factor from the dead smooth bacterial strain had taken entry into the rough strains and converted them into smooth strains. He called this factor as Transforming principle.

Later in 1944 scientists, Avery, MacLeod, and McCarty conducted an experiment to find out what the transforming principle was, They selected DNA, Proteins and RNA. They eliminated proteins by adding proteases and the strains were able to perform the transformation, they eliminated RNA with RNase the strains were still able to perform the transformation, they eliminated DNA with DNase and now the smooth strains lost the ability to transform Rough strains and hence it was proved that the DNA was the transforming principle. 
Therefore the right option is option B, DNA. 

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

Select the correct option

  1. Direction of RNA Synthesis ----- Direction of reading of template DNA Strand

    3 5------5 3

  2. Direction of RNA Synthesis ----- Direction of reading of template DNA Strand

    5 3------5 3

  3. Direction of RNA Synthesis---- Direction of reading of template DNA Strand

    3 5------3 5

  4. Direction of RNA Synthesis - ---- Direction of reading of template DNA Strand

    5 3 ----- 3 5
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

RNA synthesis occurs in the 5' to 3' direction, and the template DNA strand is read in the 3' to 5' direction to ensure antiparallel alignment.

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

The terminator/stop codons UGA, UAG and UAA

  1. Initiate translation

  2. Do not code for any amino acid

  3. Code for only one amino acid

  4. Code for more than one amino acid

  5. Initiate transcription
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

UGA, UAG, and UAA are known as stop or nonsense codons. They signal the termination of protein synthesis and do not code for any amino acid.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

The function of polymerase chain reaction (PCR) is

  1. Translation

  2. Transcription

  3. DNA amplification

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Translation is the process of synthesis of protein using mRNA nucleotide sequence as template, it occurs in cytoplasm. Transcription is the process of mRNA synthesis using DNA coding strand as template, it occurs in nucleus. PCR is a technique to amplify the gene of interest in three steps namely denaturation of target DNA (thermal cycle to separate the DNA strands), annealing of primers to the ssDNA and polymerisation (extension of primer into complete DNA strand complementary to the template strand). After completion of one cycle of PCR, two copies of the target DNA are produced both of which serve as template for next PCR cycle and produce 4 copies. Hence, there is exponential amplification of DNA copies. Correct option is C.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Enzyme required for polymerase chain reaction (PCR) is

  1. RNA polymerase

  2. Ribonuclease

  3. Taq polymerase

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

PCR requires a thermostable DNA polymerase to synthesize new DNA strands during the extension phase. Taq polymerase, isolated from Thermus aquaticus, is the standard enzyme used because it withstands high temperatures.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which of the following is not required in PCR?

  1. DNA primer

  2. DNA template

  3. RNA primer

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

DNA primer is not required for a PCR reaction. 

The reason for RNA primers to be used in PCR is the non availability of DNA primers. The RNA primers complimentary to the cellular DNA are easily synthesized by the DNA Primase enzyme which is nothing but RNA polymerase just like mRNA.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Polymerase chain reaction is used for

  1. In vivo replication

  2. In vivo synthesis of mRNA

  3. In vitro replication of DNA segment

  4. In vitro synthesis of mRNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

PCR is an in vitro technique used to replicate specific DNA segments outside of a living organism.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

PCR proceeds in three distinct steps governed by temperature. The order of the steps is 

  1. Denaturation, Synthesis, Annealing

  2. Annealing, Synthesis, Denaturation

  3. Synthesis, Annealing, Denaturation

  4. Denaturation, Annealing, Synthesis
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The three steps of PCR are: 1) Denaturation (high heat to separate strands), 2) Annealing (cooling to allow primers to bind), and 3) Extension/Synthesis (optimal temperature for polymerase to build the new strand).

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which one of the following enzymes is used in PCR reaction?

  1. Taq polymerase

  2. RNA polymerase

  3. Rib nuclease

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

Taq polymerase is the thermostable enzyme essential for the extension phase of the PCR reaction, allowing it to withstand high temperatures.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which among the following is true for protein synthesis in bacteria?

  1. It involves all the three types of RNAs (m-RNA, t-RNA and r-RNA)
  2. It involves $3$ types of RNA polymerase

  3. It involves single type of RNA polymerase

  4. It involves RNA processing
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In bacteria, transcription is performed by a single type of RNA polymerase that synthesizes all three types of RNA (mRNA, tRNA, and rRNA).

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Select the wrong pair

  1. RNA polymerase I - Sn RNA 5S rRNA, r-RNA

  2. RNA polymerase I - r-RNA

  3. RNA polymerase II - hnRNA

  4. RNA polymerase III - tRNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

RNA polymerase I is responsible for transcribing rRNA (except 5S rRNA). RNA polymerase III transcribes tRNA, 5S rRNA, and snRNA. Option A is incorrect because RNA polymerase I does not transcribe snRNA or 5S rRNA.

Multiple choice zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

"Secondary messenger" is

  1. Cyclic AMP

  2. ATP

  3. ADP

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

Cyclic adenosine monophosphate is a secondary messenger important in many biological processes. It is a derivative of ATP. When a G-protein–coupled receptor on the surface of a cell binds to its particular ligand, the receptor may stimulate the intracellular production of cAMP by the adenylyl cyclase-associated with that receptor. cAMP can then diffuse through the cytoplasm, where it interacts with various targets. Thus, cAMP serves as a second messenger within a cell.

It is used for intracellular signaling system such as transferring into cells the effects of hormones like glucagon and adrenaline, which cannot pass through the plasma membrane. It is also involved in the activation of protein kinases. Hence option A is correct.