Question 1
In marginal placentation, the placenta forms a ridge along the:[cite: 4]
✅ Correct Answer: Ventral suture of the ovary
Explanation: In marginal placentation, the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. This is characteristically seen in the Pea (Pisum sativum)[cite: 4].
Question 2
Which of the following events is NOT associated with the pachytene stage of prophase I?[cite: 4]
✅ Correct Answer: Dissolution of the synaptonemal complex
Explanation: The dissolution of the synaptonemal complex marks the beginning of the diplotene stage, not pachytene[cite: 4]. Pachytene is characterized by the appearance of recombination nodules and the enzyme-mediated process of crossing over[cite: 4].
Question 3
During embryonic development, the first sign of a growing foetus may be noticed by:[cite: 4]
✅ Correct Answer: Listening to the heart sound carefully through a stethoscope
Explanation: According to NCERT, after one month of pregnancy, the embryo's heart is formed[cite: 4]. The first sign of a growing foetus is noticed by listening to the heart sound carefully through a stethoscope[cite: 4].
Question 4
According to Robert May's global estimate, what percentage of total species have been recorded so far?[cite: 4]
✅ Correct Answer: 22%
Explanation: Robert May places the global species diversity at about 7 million[cite: 4]. According to NCERT, only about 22% of the total species have been recorded so far[cite: 4].
Question 5
If an alien piece of DNA is ligated at the BamH I site of the pBR322 vector, the resulting recombinant plasmid will:[cite: 4]
✅ Correct Answer: Lose tetracycline resistance
Explanation: The BamH I recognition site in the pBR322 vector is located within the tetracycline resistance gene (tetR)[cite: 4]. Ligation of foreign DNA at this site causes insertional inactivation, leading to a loss of tetracycline resistance[cite: 4].
Question 6
In the C4 pathway, what is the primary CO2 acceptor and the first stable product respectively?[cite: 4]
✅ Correct Answer: PEP (3-C) and OAA (4-C)
Explanation: In C4 plants, the primary CO2 acceptor is a 3-carbon molecule, phosphoenolpyruvate (PEP), present in the mesophyll cells[cite: 4]. The enzyme responsible for this fixation is PEP carboxylase[cite: 4]. The first stable product formed is the 4-carbon compound oxaloacetic acid (OAA)[cite: 4].
Question 7
During the generation of an action potential in a neuron, the rapid depolarization phase is primarily due to:[cite: 4]
✅ Correct Answer: Influx of Na+ ions
Explanation: When a stimulus is applied, voltage-gated Na+ channels open, allowing a rapid influx of Na+ into the axoplasm[cite: 4]. This reverses the polarity across the membrane, causing depolarization and generating an action potential[cite: 4].
Question 8
In eukaryotes, the enzyme RNA polymerase III is responsible for the transcription of:[cite: 4]
✅ Correct Answer: tRNA, 5S rRNA, and snRNAs
Explanation: In eukaryotes, RNA Polymerase I transcribes rRNAs (28S, 18S, 5.8S), RNA Polymerase II transcribes the precursor of mRNA (hnRNA), and RNA Polymerase III is responsible for the transcription of tRNA, 5S rRNA, and snRNAs[cite: 4].
Question 9
Assertion (A): In a dihybrid test cross for two completely linked genes, the parental combinations appear in higher frequency than the non-parental types.
Reason (R): Linked genes are located on the same chromosome and do not assort independently.[cite: 4]
✅ Correct Answer: Both A and R are true and R is the correct explanation of A.
Explanation: Linked genes are physically located on the same chromosome, which prevents them from assorting independently during meiosis (violating Mendel's Law of Independent Assortment)[cite: 4]. Because of this linkage, the parental allele combinations tend to stay together, leading to a much higher frequency of parental types compared to recombinants[cite: 4].
Question 10
Assertion (A): The spleen acts as a filter of the blood by trapping blood-borne microorganisms.
Reason (R): The spleen is a primary lymphoid organ where B lymphocytes mature.[cite: 4]
✅ Correct Answer: A is true but R is false.
Explanation: The spleen does act as a filter of the blood by trapping blood-borne pathogens (Assertion is true)[cite: 4]. However, the spleen is a secondary lymphoid organ, not a primary one[cite: 4]. Primary lymphoid organs (where maturation occurs) are the bone marrow and thymus (Reason is false)[cite: 4].
Question 11
Consider the following statements about Glycolysis:
Statement I: ATP is utilized at two steps in the glycolysis pathway.
Statement II: A water molecule is removed during the conversion of 2-phosphoglycerate to phosphoenolpyruvate.[cite: 4]
✅ Correct Answer: Both Statement I and Statement II are correct.
Explanation: ATP is utilized in two steps: conversion of Glucose to Glucose-6-phosphate, and Fructose-6-phosphate to Fructose 1,6-bisphosphate (Statement I is correct)[cite: 4]. An enolase enzyme catalyzes the removal of a water molecule from 2-phosphoglycerate to form phosphoenolpyruvate (Statement II is correct)[cite: 4].
Question 12
Consider the following statements about enzymes:
Statement I: The co-factor for the proteolytic enzyme carboxypeptidase is zinc.
Statement II: Prosthetic groups are organic compounds that are only transiently bound to the apoenzyme.[cite: 4]
✅ Correct Answer: Statement I is correct, Statement II is incorrect.
Explanation: Zinc is a metal ion co-factor for carboxypeptidase (Statement I is true)[cite: 4]. Prosthetic groups are organic compounds that are tightly bound to the apoenzyme (e.g., haem in peroxidase)[cite: 4]. Co-enzymes (like NAD) are the ones that bind transiently (Statement II is false)[cite: 4].
Question 13
A double-stranded DNA molecule contains 20% cytosine. What will be the percentage of adenine in this DNA?[cite: 4]
✅ Correct Answer: 30%
Explanation: According to Chargaff's rule, the amount of Cytosine (C) equals Guanine (G), and Adenine (A) equals Thymine (T)[cite: 4]. If C = 20%, then G = 20%. Total C + G = 40%[cite: 4]. Remaining DNA = 100% - 40% = 60%. Since A = T, Adenine = 60% / 2 = 30%[cite: 4].
Question 14
In a freely mating population of 1000 individuals, 360 belong to genotype AA, 480 to Aa, and 160 to aa. What is the frequency of allele 'A' in this population?[cite: 4]
✅ Correct Answer: 0.6
Explanation: Using the Hardy-Weinberg equation ($p^2 + 2pq + q^2 = 1$): The frequency of genotype AA ($p^2$) = 360/1000 = 0.36[cite: 4]. Therefore, the frequency of allele 'A' ($p$) = $\sqrt{0.36} = 0.6$[cite: 4]. (You can verify: $q^2 = 160/1000 = 0.16$, so $q = 0.4$, and $p+q=0.6+0.4=1.0$)[cite: 4].
Question 15
If the initial amount of DNA in a cell is denoted as 2C at the G1 phase, what will be the amount of DNA after the S phase and at the end of Anaphase II of meiosis, respectively?[cite: 4]
✅ Correct Answer: 4C and 1C
Explanation: During the S phase, DNA replicates, so the amount doubles from 2C to 4C[cite: 4]. At the end of Meiosis I, the DNA content halves to 2C per cell[cite: 4]. After Anaphase II (Meiosis II), sister chromatids separate, and the resulting gametes/cells have 1C DNA content each[cite: 4].
Question 16
Match the microbes with their commercially produced organic acids...[cite: 4]
✅ Correct Answer: a-iv, b-iii, c-ii, d-i
Explanation: Aspergillus niger (a fungus) produces citric acid (iv)[cite: 4]. Acetobacter aceti (a bacterium) produces acetic acid (iii)[cite: 4]. Clostridium butylicum (a bacterium) produces butyric acid (ii)[cite: 4]. Lactobacillus (a bacterium) produces lactic acid (i)[cite: 4].
Question 17
Which one of the following population interactions is widely exploited in medical science for the production of antibiotics?[cite: 4]
✅ Correct Answer: Amensalism
Explanation: Amensalism is an interaction where one species is harmed while the other is unaffected (-, 0)[cite: 4]. The production of antibiotics by fungi (like Penicillium) kills or inhibits bacteria (harmed), while the fungus itself does not gain any direct nutritional benefit from the dead bacteria[cite: 4].
Question 18
In a dicot root, the vascular cambium is completely secondary in origin. It originates from:[cite: 4]
✅ Correct Answer: The tissue located just below the phloem bundles and a portion of pericycle tissue above the protoxylem.
Explanation: In dicot roots, the vascular cambium is completely secondary in origin[cite: 4]. It originates from the conjunctive tissue located just below the primary phloem bundles, along with a portion of the pericycle tissue present above the protoxylem, forming a complete and continuous wavy ring[cite: 4].
Question 19
Which of the following cell junctions functions primarily to prevent leakage of bodily fluids across tissue layers?[cite: 4]
✅ Correct Answer: Tight junctions
Explanation: Tight junctions help to stop substances from leaking across a tissue[cite: 4]. Adhering junctions perform cementing to keep neighbouring cells together[cite: 4]. Gap junctions facilitate communication between cells by connecting their cytoplasm[cite: 4].
Question 20
Viroids differ from viruses in that viroids have:[cite: 4]
✅ Correct Answer: RNA molecules without a protein coat
Explanation: Viroids were discovered by T.O. Diener (1971)[cite: 4]. They are infectious agents smaller than viruses[cite: 4]. They cause potato spindle tuber disease and consist of free, low-molecular-weight RNA without the protein coat (capsid) that is typically found in viruses[cite: 4].
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