Q641. Down syndrome is a genetic disorder caused by the presence of an extra copy of which chromosome?
Science and Technology: RAS Prelims MCQs
1113 RAS Prelims practice MCQs on science and technology are on this page, in 6 chapters. They cover the basics of everyday science, computers and information technology, defence and space technology in India, genetics, biotechnology and nanotechnology, science and technology policies and government programmes, and recent advances with Indian contributors and indigenisation. Each question has an answer and an explanation.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
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Q642. Match List-I with List-II regarding genetic disorders:
| Genetic Disorder | Cause/Characteristic |
|---|---|
| A. Sickle cell anaemia | i. X-linked recessive disorder preventing blood clotting |
| B. Haemophilia | ii. Point mutation in the beta-globin chain |
| C. Down syndrome | iii. Absence of one X chromosome in females (45, X0) |
| D. Turners syndrome | iv. Trisomy 21 |
Explanation
Overview of Human Genetic Disorders P. Sickle cell anemia is caused by a specific point mutation in the beta-globin chain. Q. Haemophilia is an X-linked recessive disorder that inhibits proper blood clotting. R. Down syndrome arises from the trisomy of chromosome twenty-one. S. Turners syndrome involves the absence of one X chromosome in females, resulting in forty-five total chromosomes.
Q643. Sickle cell anaemia is characterized by the substitution of glutamic acid by which amino acid in the beta-globin chain of haemoglobin?
Explanation
In sickle cell anemia, a specific point mutation occurs in the HBB gene encoding the beta-globin chain of hemoglobin. At the sixth position of the polypeptide chain, the amino acid glutamic acid is replaced by valine.
Q644. Which of the following represents the correct sequence of events leading to sickle cell anaemia?
Explanation
The development of sickle cell anemia begins with a point mutation in the DNA, which is then transcribed into an altered mRNA codon. This results in the substitution of valine for glutamic acid in the hemoglobin protein. In low oxygen environments, these mutant hemoglobin molecules aggregate and polymerize. This internal structural change forces the red blood cell to transform from a disc to a sickle shape.
Q645. Haemophilia is often referred to as the Royal Disease. It is genetically transmitted as an:
Explanation
Haemophilia is a genetic disorder that impairs the bodys ability to make blood clots, a process needed to stop bleeding. It is inherited as an X-linked recessive trait. This means the gene is located on the X chromosome. Because males have only one X chromosome, they are more frequently affected, while females are usually asymptomatic carriers unless they inherit two copies of the defective gene.
Q646. Identify the correct pair regarding human genetic disorders:
Explanation
Klinefelters syndrome is a genetic condition that occurs when a male is born with an extra copy of the X chromosome, resulting in a 47, XXY karyotype. Turners syndrome is 45, X0 (monosomy X). Sickle cell anemia is an autosomal recessive disorder, not X-linked. Hemophilia is an X-linked recessive disorder, whereas Trisomy 13 is known as Patau syndrome, highlighting the distinct nature of these disorders.
Q647. Individuals heterozygous for the sickle cell trait have a survival advantage against which infectious disease?
Explanation
Individuals who are heterozygous for the sickle cell allele possess a significant survival advantage in regions where malaria is endemic. The presence of the sickle hemoglobin makes their red blood cells less hospitable to the Plasmodium parasite. This phenomenon, known as heterozygote advantage, explains why the sickle cell gene remains prevalent in certain populations despite the severity of the homozygous disease.
Q648. The failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to conditions like Down syndrome, is called:
Explanation
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, specifically during meiosis I or II. This error leads to gametes with an abnormal number of chromosomes, either too many or too few. When such a gamete participates in fertilization, it results in aneuploid conditions such as Down syndrome (trisomy) or Turners syndrome (monosomy).
Q649. A woman who is a carrier for haemophilia marries a normal man. What is the probability that their son will have haemophilia?
Explanation
A carrier woman has one normal X chromosome and one X chromosome with the haemophilia allele. A normal man has XY. Their sons receive a Y from the father and either the normal X or the Xh from the mother. Therefore, there is a fifty percent chance that a son will inherit the Xh chromosome and have haemophilia. The daughters would be either normal or carriers.
Q650. Genetic engineering primarily involves the manipulation of:
Explanation
Genetic engineering is a field of biotechnology that primarily involves the direct manipulation of an organisms deoxyribonucleic acid (DNA). By using molecular tools to cut, copy, and move specific segments of DNA, scientists can alter the genetic makeup of cells and organisms. This allows for the introduction of new traits, the removal of undesirable ones, or the mass production of essential biological products.Answer key for these questions
| Q | Correct answer |
|---|---|
| 641 | (d) Chromosome 21 |
| 642 | (a) A-ii, B-i, C-iv, D-iii |
| 643 | (c) Valine |
| 644 | (a) Point mutation in DNA - Altered mRNA - Altered amino acid sequence - Polymerization of haemoglobin under low oxygen - RBC shape changes |
| 645 | (a) X-linked recessive trait |
| 646 | (c) Klinefelters syndrome - 47, XXY |
| 647 | (b) Malaria |
| 648 | (c) Nondisjunction |
| 649 | (d) 50% |
| 650 | (c) Deoxyribonucleic acid (DNA) |
Key facts from Science and Technology
- The RPSC paper is General Knowledge and General Science, so science questions come with a strong dose of applied and recent topics.
- Everyday science questions test the laws and terms of physics, chemistry and biology through examples.
- Defence and space questions pair a missile, satellite or mission with its year and organisation.
- Policy questions ask for the year, the body and the aim of schemes like STIP, the National Quantum Mission and BioE3.
- Health, environment and agriculture are on a separate page, with their own chapters.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Science and Technology?
This page has 1113 practice MCQs on Science and Technology. Each has the correct answer, and most have an explanation.
Which chapters does the science and technology set cover?
Six chapters: basics of everyday science; computers, information and communication technology; defence and space technology in India; genetics, biotechnology and nanotechnology; science and technology policies and government programmes; and recent advances, Indian contributors and indigenisation.
Is science and technology part of the RAS Prelims syllabus?
Yes. The RPSC paper is called General Knowledge and General Science, and its syllabus lists science and technology topics along with environment, health, agriculture and government programmes, so questions can come from any of these areas.
How should I prepare science for RAS Prelims?
Revise the concepts by examples, then learn the missions, schemes and scientists with their year and organisation. Attempt each chapter, read the explanations and keep a list of the facts you missed.