Biology

Molecular Genetics

917 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

A codon is read in

  1. 3 5 direction

  2. 5 3' direction

  3. 3 6' direction

  4. 6' 3' direction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Codons are read in the 5' to 3' direction on the mRNA molecule during translation. This is the same direction as RNA synthesis during transcription. The ribosome moves along the mRNA from 5' end toward 3' end, reading each codon sequentially. Options A and C have incorrect notation (3' 5', 3' 6'). Option D has non-standard notation (6'). Option B is correct.

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

Khorana et al synthesised RNA with copolymer of UGUGUGUGUG... It produced a peptide with alternate cysteine and valine. The codons for the two are

  1. UGU and GUG

  2. UUG and GGU

  3. GUG and UGU

  4. UGG and GUU
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A repeating UGUGUG... sequence produces codons UGU and GUG. UGU codes for cysteine and GUG codes for valine, matching the observed peptide.

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

Central dogma of protein synthesis consists of

  1. $DNA \overset{translation}{\rightarrow} mRNA \overset{transcriptionlation}{\rightarrow} Protein$
  2. $DNA \overset{transcription}{\rightarrow} mRNA \overset{translation}{\rightarrow} Protein$
  3. $RNA \overset{replication}{\rightarrow} DNA \overset{translation}{\rightarrow} Protein$
  4. $RNA \overset{transcriptions}{\rightarrow} mRNA \overset{translation}{\rightarrow} Protein$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The central dogma states that genetic information flows from DNA to RNA via transcription, and from RNA to protein via translation.

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'.