Q2601. Which event marked the political decline of the independent Rajput states, leading them into subordinate treaties with the British?
RAS Prelims MCQ Practice
9,654 RAS Prelims practice MCQs with the correct answer and a clear explanation for each. Filter by subject and chapter.
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Q2602. Repeated sequences make up a large portion of the human genome. What is their primary role?
Explanation
Repetitive sequences, which do not code for proteins, make up a very large portion of the human genome. While they were once dismissed as junk DNA, research has shown that they play critical roles in maintaining chromosome structure, dynamics, and stability. They provide essential information for chromosome folding and organization within the nucleus and may also be involved in regulating gene expression.
Q2603. CRISPR-Cas9 is a revolutionary technology primarily used for:
Explanation
CRISPR-Cas9 is a revolutionary tool that allows scientists to make highly specific and precise changes to the DNA of living organisms. Often described as molecular scissors, it can be programmed to find a specific genetic sequence and cut it, allowing for genes to be removed or new sequences to be added. This technology has transformed genetic research and offers potential future cures.
Q2604. Given below are two statements, one labeled as
Assertion (A) and the other as Reason (R):
Assertion (A): CRISPR-Cas9 was originally discovered as an adaptive immune system in bacteria.
Reason (R): Bacteria use CRISPR-Cas9 to remember and cut the DNA of invading viruses (bacteriophages).
Select the correct answer from the codes given below:
Assertion (A) and the other as Reason (R):
Assertion (A): CRISPR-Cas9 was originally discovered as an adaptive immune system in bacteria.
Reason (R): Bacteria use CRISPR-Cas9 to remember and cut the DNA of invading viruses (bacteriophages).
Select the correct answer from the codes given below:
Explanation
CRISPR-Cas9 was not originally an artificial invention but was discovered as a natural adaptive immune system in bacteria and archaea. Bacteria use CRISPR sequences to store fragments of DNA from viruses that have previously attacked them. If the same virus invades again, the Cas9 enzyme uses the stored RNA memory to recognize and cut the viral DNA, effectively neutralizing the threat.
Q2605. Who among the following were awarded the Nobel Prize in Chemistry in 2020 for the development of the CRISPR-Cas9 method for genome editing?
Explanation
Emmanuelle Charpentier and Jennifer Doudna were awarded the Nobel Prize in Chemistry in 2020 for their pioneering work in developing the CRISPR-Cas9 gene-editing method. They showed that the bacterial defense system could be repurposed into a versatile and programmable tool for editing any DNA sequence in any organism. Their discovery has had an immense impact on life sciences and medicine.
Q2606. In the acronym CRISPR, what does the R stand for?
Explanation
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. The R stands for Repeats, referring to the identical, short sequences of DNA that are repeated at regular intervals within the bacterial genome. These repeats are separated by spacer DNA derived from past viral invaders. This structural organization is the hallmark of this microbial immune system and provides the basis for targeting.
Q2607. A major potential application of CRISPR-Cas9 technology in human medicine is:
Explanation
The most promising medical application of CRISPR-Cas9 technology is the potential to treat and even cure inherited genetic disorders by directly correcting the underlying mutations. By targeting the defective gene in a patients cells and replacing it with a healthy sequence, CRISPR could offer permanent solutions for conditions like sickle cell anemia and cystic fibrosis, which currently have limited treatment options.
Q2608. What happens immediately after Cas9 makes a double-strand break in the target DNA?
Explanation
Once the Cas9 enzyme creates a double-strand break in the target DNA, the cells internal repair machinery is immediately activated to fix the damage. Scientists exploit these natural processes to edit the genome. One pathway often introduces small errors, effectively disabling the gene, while another pathway can use a provided DNA template to precisely insert a new sequence at the break site.
Q2609. Off-target effects in CRISPR technology refer to:
Explanation
A major challenge in CRISPR technology is the occurrence of off-target effects, which happen when the Cas9 enzyme binds to and cuts DNA at locations other than the intended target. This occurs because the guide RNA may accidentally recognize sequences that are very similar to the target site. These unintended cuts can lead to harmful mutations elsewhere in the genome, raising safety concerns.
Q2610. Gene drive is a controversial application of CRISPR that allows:
Explanation
A gene drive is a sophisticated application of CRISPR that ensures a specific genetic modification is passed on to nearly all offspring, bypassing traditional inheritance. This allows the modification to spread rapidly through an entire wild population. While it could be used to eliminate disease-carrying mosquitoes, it raises significant ethical and ecological concerns due to its potential to permanently alter entire ecosystems.Answer key for these questions
| Q | Correct answer |
|---|---|
| 2601 | (a) Military defeat of the Rajput confederacy by Marathas at Merta |
| 2602 | (d) Contribution to understanding the chromosome structure |
| 2603 | (c) Targeted and precise gene editing |
| 2604 | (a) Both A and R are true and R is the correct explanation of A. |
| 2605 | (a) Emmanuelle Charpentier and Jennifer Doudna |
| 2606 | (d) Repeats |
| 2607 | (b) Curing genetic diseases by correcting mutations |
| 2608 | (a) The cell’s natural DNA repair mechanisms try to fix the break. |
| 2609 | (c) Cas9 cutting DNA at unintended sites with similar sequences |
| 2610 | (d) Promoting universal inheritance of a genetic alteration |
Frequently asked questions
How many RAS Prelims practice MCQs are there on RAS Prelims?
This page has 9654 practice MCQs on the RAS Prelims syllabus. Each has the correct answer, and most have an explanation.
How should I practise MCQs for RAS Prelims?
Attempt each question first, then open the answer and read the explanation. Practise one chapter at a time, note the facts you got wrong and revise them. Repeat the chapter after a few days.
Are these actual RAS Prelims past-paper questions?
No. These are practice questions written for the RAS Prelims syllabus. They follow the pattern the exam uses: factual questions, statement-based questions, match-the-list and assertion-reason.