GS: Hindi / English · Language questions stay in their original language.
120 questions · 120 marks · 2 hours
Choose one option per question.
Tap an option to check it, or open “See answer”.
Correct answer: (A) Tyrosine
Tyrosine carries a hydroxyl group to which a phosphate can be attached, which is why it is a target of kinase action.
Correct answer: (E) None of the above
The movement of a DNA segment from one place in the genome to another is called transposition, which is not among the options.
Correct answer: (E) None of the above
The DNA-binding protein that initiates the transcription of a bacterial gene is a sigma factor or an activator. An operator and a promoter are sites on the DNA, not proteins—so the answer is ‘None of these’.
Correct answer: (A) A given base triplet can code for more than one amino acid
The genetic code being degenerate means that one amino acid is specified by more than one triplet codon—one amino acid, several possibilities.
Correct answer: (A) Small and inbred
Genetic drift is greatest in a small, inbreeding population, where gene frequencies shift by chance alone.
Correct answer: (E) None of the above
A cross between a hybrid and either of its parents is a backcross. A test cross is made only with the recessive parent—so the answer is ‘None of these’.
Correct answer: (B) Law of segregation
Selfing a heterozygous tall plant gives both tall and dwarf offspring, which shows that the two factors separated when the gametes formed—this is the law of segregation.
Correct answer: (B) Ecological equivalents
Organisms that fill the same ecological niche in different geographical regions are called ecological equivalents.
Correct answer: (E) None of the above
Abies, Quercus and Rhododendron are all trees of temperate or montane forest, not of the tropical dry deciduous forest. So the answer is ‘None of these’.
Correct answer: (E) None of the above
The correct sequence of succession is nudation, invasion, reaction and then stabilization. No option gives that order.
Correct answer: (C) Many plant species may not be able to shift their ranges at the same pace as the northward movement of temperature zones.
Conservation biologists hold that warming will reduce the number of species, because many plants cannot shift their range as fast as the climate is changing.
Correct answer: (A) Gross primary productivity
The total rate of photosynthesis, including the organic matter spent in respiration, is the gross primary productivity.
Correct answer: (B) Digested into its nucleotides
In the lytic cycle of a bacteriophage the host DNA is broken down into nucleotides, out of which the virus builds its own DNA.
Correct answer: (A) Temperate virus
A virus that goes on multiplying along with the host genome without killing the host is called a temperate virus.
Correct answer: (B) Lophotrichous
A bacterium with a tuft of flagella at one end is called lophotrichous.
Correct answer: (E) None of the above
The exchange of DNA between two bacteria through a cytoplasmic bridge is conjugation, which is not among the options.
Correct answer: (A) Clostridium
Botulism is caused by Clostridium botulinum, an anaerobe that thrives in canned food.
Correct answer: (A) Downy mildew
A disease in which the pathogen shows as a cottony growth on the surface of the host is called downy mildew.
Correct answer: (A) Endemic
A disease that persists in an area year after year in much the same form is said to be endemic.
Correct answer: (D) More than one of the above
Achromobacter, Micrococcus and Alteromonas can all degrade petroleum hydrocarbons, so the answer is ‘more than one’.
Correct answer: (C) Nostoc
Nostoc is a blue-green alga which fixes nitrogen and so serves as a biofertilizer in paddy fields.
Correct answer: (B) Lycopsida
The first forest on earth was made of plants of the class Lycopsida, among them giant trees such as Lepidodendron.
Correct answer: (C) Trichodesmium
Trichodesmium is marine—the colour of the Red Sea is put down to it. Nostoc and Scytonema are found in fresh water.
Correct answer: (E) None of the above
The balloon-like outgrowths that push from the wall of a xylem vessel into its lumen are tyloses, which is not among the options.
Correct answer: (B) Drupe
When the ovary wall ripens into a pericarp with a stony endocarp and a fleshy mesocarp, the fruit is a drupe—the mango, for instance.
Correct answer: (B) Cycas
The neurotoxin BMAA is found in the seeds of Cycas.
Correct answer: (A) Bentham and Hooker
‘Genera Plantarum’, in three volumes, is the work of Bentham and Hooker, and gives a natural classification of the flowering plants.
Correct answer: (E) None of the above
Free nuclear division in the developing endosperm occurs in most angiosperms, but in none of the three examples given—so the answer is ‘None of these’.
Correct answer: (E) None of the above
In a dicot seed the growing seedling is fed by the cotyledons, which are not among the options.
Correct answer: (B) Development of an organ from a cell in a culture medium
Totipotency means that a single cell can, in a culture medium, develop into a whole organ or plant.
Correct answer: (C) Fertilization in which the pollen tube enters the ovule through the micropyle
Porogamy is fertilization in which the pollen tube enters the ovule through the micropyle—the usual route.
Correct answer: (C) Meristem
A virus seldom reaches the cells of the meristem, which is why meristem culture is used to raise virus-free plants.
Correct answer: (E) None of the above
An embryo arising from the cells of the nucellus is called adventive embryony, which is not among the options.
Correct answer: (A) Oenothera
Members of the family Onagraceae have the Oenothera type of embryo sac, with four nuclei.
Correct answer: (C) Without fusion of gametes
Apomixis means the development of a new plant without the fusion of gametes—seed or embryo formed without fertilization.
Correct answer: (C) Basidiocarp
The part of a mushroom that shows above the ground is the basidiocarp, in which the spores are formed.
Correct answer: (D) More than one of the above
Gelidium and Gracilaria are both red algae, and agar comes from them. Ulothrix is a green alga, so the answer is ‘more than one’.
Correct answer: (A) Kigelia sp.
The large night-opening flowers of Kigelia are pollinated by bats.
Correct answer: (B) Cork cambium
Cork cambium is a secondary meristem, since it arises later out of permanent tissue. Protoderm and procambium are primary meristems.
Correct answer: (E) None of the above
Companion cells are found with the sieve tubes, which belong to the phloem. All three given are associated with xylem, so the answer is ‘None of these’.
Correct answer: (C) C-DNA
DNA synthesized on an RNA template is complementary DNA, cDNA—written here as C-DNA.
Correct answer: (D) More than one of the above
UAA, UAG and UGA are all nonsense codons, which stop translation. So the answer is ‘more than one’.
Correct answer: (E) None of the above
The total stem parasite is Cuscuta. Orobanche and Rafflesia are root parasites and Loranthus a partial one—so the answer is ‘None of these’.
Correct answer: (E) None of the above
A monosomic condition is 2n − 1, one chromosome short. That is not among the options.
Correct answer: (C) Anaphase
Chromosomes are drawn to the poles at anaphase, when the spindle fibres begin to shorten.
Correct answer: (D) More than one of the above
Respiring fats and proteins takes more oxygen, so their respiratory quotient stays below one—more than one option is right.
Correct answer: (E) None of the above
Aconitase, fumarase and decarboxylase all work in the Krebs cycle, so the answer is ‘None of these’.
Correct answer: (C) AUG
AUG is the initiation codon; it also codes for methionine and starts translation.
Correct answer: (C) Four
India is counted as having four biodiversity hotspots—the Himalaya, the Western Ghats, Indo-Burma and Sundaland (the Nicobars).
Correct answer: (D) More than one of the above
Neottia and Monotropa are both saprophytic angiosperms, living off decayed matter. Cuscuta is a parasite, so the answer is ‘more than one’.