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 bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Which one is RNA dependent DNA polymerase

  1. RNA polymerase I

  2. Tag polymerase

  3. DNA polymerase

  4. Reverse transcriptase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Reverse transcriptase is the RNA-dependent DNA polymerase that synthesizes DNA from an RNA template. RNA polymerase I and DNA polymerase are not RNA-dependent. Tag polymerase appears to be a typo (likely Taq polymerase), which is a DNA-dependent DNA polymerase used in PCR.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Teminious central dogma of protein synthesis is

  1. DNA DNA mRNA protein

  2. mRNA gRNA DNA Protein

  3. gRNA DNA mRNA Protein

  4. DNA gRNA mRNA Protein
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This represents the flow in retroviruses: genomic RNA (gRNA) is reverse transcribed to DNA, which is then transcribed to mRNA and translated to protein. Option A is standard replication, B is incorrect (gRNA to DNA requires reverse transcription), and D has incorrect flow order.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Which of the following information transfers is catalyzed the reverse transcriptase?

  1. RNA $\rightarrow$ RNA
  2. RNA $\rightarrow$ DNA
  3. DNA $\rightarrow$ DNA

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

Reverse transcriptase is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed reverse transcription. A retrovirus is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades thus changing the genome of that cell. Once inside the host cell cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern and thus retro (backward).

So, the correct option is ' RNA $\rightarrow$ DNA'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Some RNA viruses carry a gene or an enzyme that uses viral RNA as a template in the synthesis of DNA. This enzyme is 

  1. RNA replicase

  2. Reverse transcriptase

  3. Viral nuclease

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

Reverse transcriptase catalyzes the formation of double-stranded deoxyribonucleic acid (DNA) from a single-stranded ribonucleic acid (RNA) genome. It is called "reverse" transcriptase because it reverses the usual direction of information flow, from DNA to RNA. Reverse transcriptase enzymes can be found in viruses, which use reverse transcriptase to make more viruses.

So, the correct option is 'Reverse transcriptase'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

In cloning experiments, cDNA molecules can be obtained from an mRNA copy by

  1. Polymerase chain reaction

  2. Reverse transcriptase

  3. Ribozyme

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

Complementary DNA (cDNA) is a DNA copy of a messenger RNA (mRNA) molecule produced by reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes.  cDNA is also produced naturally by retroviruses (such as HIV) for integration into the host's genome.

So, the correct option is 'Reverse transcriptase'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Choose the correct answers from the alternatives given :
The central dogma of molecular biology

  1. states that DNA is a template for all RNA production

  2. pertains only to prokaryotes because humans are unique

  3. states that translation precedes transcription

  4. states that DNA is a template only for DNA replication
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During the transcription phase of the central dogma, DNA acts as the template for RNA synthesis. The RNA polymerase enzyme identifies the base on the DNA strand and adds a complementary base to the sequence. After transcription, translation of mRNA occurs that leads to the formation of the polypeptide sequence.

So, the correct option is 'states that DNA is a template for all RNA production'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

During transcription, the site of DNA molecule at which RNA polymerase binds is called

  1. promoter

  2. regulator

  3. receptor

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

The RNA polymerase enzyme binds to a specific site called promoter and initiates transcription. The promoter region determines which DNA strand is to be transcribed. Thus, a promoter region has RNA polymerase recognition site and RNA polymerase binding site.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

The molecule needed to allow a cell to transfer genetic information from RNA to DNA, is

  1. DNA polymerase

  2. RNA polymerase

  3. reverse transcriptase

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

Reverse transcriptase is an enzyme used to generate complementary DNA from an RNA template, a process termed reverse transcription. Reverse transcriptase enzymes can be found in viruses, which use reverse transcriptase to make more viruses. 

So, the correct option is 'reverse transcriptase'.

Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Silencing of a gene could be achieved through the use of

  1. RNAI only

  2. Antisense RNA only

  3. Both RNAi and antisense RNA

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
So, the correct answer is 'Both RNAi and antisense RNA'.
Multiple choice bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

Which of the following is correct match of phenomenon and its explanation?

  1. Central dogma$\rightarrow$ RNA$\rightarrow$ DNA $\rightarrow$ Protein$\rightarrow$ RNA
  2. Reverse transcription$\rightarrow$ PCR$\rightarrow$ DNA amplification
  3. Transcription$\rightarrow$ Formation of RNA and proteins
  4. RNA silencing$\rightarrow$ Use of dsRNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Reverse transcription polymerase chain reaction (RT-PCR) uses mRNA rather than DNA as the starting template. First, the enzyme reverse transcriptase uses the mRNA template to produce a complementary single-stranded DNA strand called cDNA in a process known as reverse transcription. Next, DNA polymerase is used to convert the single-stranded cDNA into double-stranded DNA. These DNA molecules can now be used as templates for a polymerase chain reaction ( PCR ) for DNA amplification.

Central dogma can be correctly represented as DNA→ DNA→ RNA → Protein. 
Transcription is the formation of RNA from DNA. 

So, the correct option is 'Reverse transcription→ PCR→ DNA amplification'.