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

The subunits of a prokaryotic ribosome are

  1. 60S and 40S

  2. 50S and 30S

  3. 60S and 50S

  4. 20S and 15S
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The subunits of a prokaryotic ribosome are 50S and 30S. The 70S ribosomes of prokaryotes have in the larger 50S subunit, 23S and 5S types of rRNA and 34 different proteins. The 30S subunit contains a molecule of 16S rRNA and 21 different proteins.

Multiple choice

Prokaryotic ribosomes are

  1. 70 S

  2. 80 S

  3. 55 S

  4. 40 S
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The ribosomes of prokaryotic cells are smaller than eukaryotic ribosomes. Prokaryotic ribosomes measure 70 S units.

Multiple choice

Tobacco mosaic virus is

  1. a single stranded RNA virus

  2. a single stranded DNA virus

  3. a double stranded RNA virus

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

 The genetic material in tobacco mosaic virus is a single stranded RNA. 

Multiple choice

Directions: Read the following passage/information and answer the question that follows.

Many researchers believe that the presence of RNA in brain cells is the biochemical basis of memory, i.e. the presence of RNA enables us to remember. Because certain chemicals are known to inhibit the synthesis of RNA in the body, we can test this hypothesis. Animals that have learned particular responses can be injected with an RNA inhibitor and then tested for memory of the learned responses.

Which of the following test results would most seriously weaken the case for RNA as the basis of memory?

  1. After an injection of RNA inhibitor, a wide range of behaviours, in addition to the learned responses, were affected.

  2. After an injection of RNA inhibitor, animals that had not consistently been giving the learned responses were able to give them consistently.

  3. After injections of RNA inhibitor, some animals lost memory of the learned responses totally, but others lost it only partially.

  4. After a small injection of RNA inhibitor, animals responded well, but as the size of the injection increased, they gave fewer of the learned responses.

  5. After an injection of RNA inhibitor, animals exhibited variation in the learned responses over a period of time.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The researchers believe that the presence of RNA enables us to remember. However, if, after an injection of RNA inhibitor, animals gave learned responses more consistently than before, it would appear that the absence of RNA facilitates memory. Therefore, the correct answer is 2.  1 is incorrect. These results would suggest that RNA is the basis of other abilities in addition to that of memory, but there is nothing in them that would weaken the case for RNA as the basis of memory. 3 is not correct. These results support the case that RNA is the basis of memory, although they suggest that the degree of effectiveness of either RNA or RNA inhibitor may vary. 4 is incorrect. These results would suggest that RNA must be strongly inhibited in order to impair memory, but still support the case for RNA as the basis of memory.  The last option is also incorrect. These results would suggest that RNA is necessary for new learning and as the learning would require memory, the results would support the case for RNA as the basis of memory.

Multiple choice

Which among the following mechanisms of transcription can interact between RNA polymerase and a particular promoter?

  1. Silencers

  2. Enhancers

  3. General transcription factors

  4. Activators

  5. Specificity factors
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Enhancers are sites on the DNA helix that are bound to by activators in order to loop the DNA bringing a specific promoter to the initiation complex. Enhancers are much more common in eukaryotes than prokaryotes.

Multiple choice

In eukaryotes during gene expression, there are several methods to look at the various stages. Which one among the following does not characterises a gene expression in eukaryotes?

  1. Protein levels can be analysed by mass spectrometry.

  2. RNA degradation rates are measured by means of transcription inhibitors.

  3. Epistatic interactions can be investigated by splicing array.

  4. The local chromatin environment of the region can be determined by ChIP-chip analysis.

  5. Due to post-transcriptional regulation, transcription rates and total RNA levels differ significantly.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Alternative splicing can be analysed with a splicing array or with a tiling array. Epistatic interactions can be investigated by synthetic genetic array analysis.

Multiple choice

Assertion: In capping, methyl guanosine triphosphate is added to the 3'-end of hnRNA. Reason: In tailing, adenylate residues are added at 5'-end in a template independent manner.

Directions: In the following question there are two statements, Assertion (A) and Reason (R), consider both the statements independently and mark your answers as under:

1. A and R both are correct and R is correct explanation of A.
2. A and R both are correct and R is not correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R both are incorrect.

  1. Both A and R are correct and R is the correct explanation of A.

  2. A and R both are correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. Both A and R are incorrect.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Both are incorrect statements. In capping, methyl guanosine triphosphate is added to the 5'-end of hnRNA. In tailing, adenylate residues are added at 3'-end in a template independent manner. It is the fully processed hnRNA, now called mRNA, that is transported out of the nucleus for translation.

Multiple choice

Which of the following statements does NOT characterise RNA editing in both plants and animals?

  1. After editing, all amino acids at the number 228 position are converted to cysteine.

  2. The RNA editing events occur at random in the transcript.

  3. The primary benefit of RNA editing could be evolutionary conservation of protein structure.

  4. Plant mitochondria do not use the universal genetic code.

  5. Editing converts a tryptophan codon to methionine codon.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Structural RNAs such as tRNAs and rRNAs are also affected. Editing can convert a tryptophan codon to arginine codon (CGG to UGG).

Multiple choice

Chemical composition of ribosome is

  1. DNA and RNA

  2. RNA and proteins

  3. DNA, RNA and Proteins

  4. DNA and histones
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ribosomes are ribonucleoprotein complexes consisting primarily of ribosomal RNA (rRNA) and ribosomal proteins. They are the site of protein synthesis in the cell.

Multiple choice

Jumping genes are referred as

  1. exons

  2. introns

  3. mutons

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

Transposons, often called jumping genes, are DNA sequences that can change their position within a genome. They were first discovered by Barbara McClintock in maize.