I. Consists of two parallel membranes. II. Perinuclear space is 10 to 50 nm. III. Forms a barrier between nuclear materials and cytoplasm. IV. Lacks any pores or openings.
Which statements are correct?
The nuclear envelope consists of two parallel membranes separated by a perinuclear space of about 10–50 nm. It forms a barrier between the nucleus and cytoplasm. Statement IV is incorrect because the nuclear envelope is interrupted by nuclear pores.
Question 62 of 100
📘 CLASS XI
Consider statements regarding nuclear pores:
I. Formed by fusion of inner and outer nuclear membranes. II. Act as passages for movement of RNA and proteins. III. Allow movement in both directions between nucleus and cytoplasm. IV. Block mRNA transport out of the nucleus completely.
Which statement combination is correct?
Nuclear pores are formed by fusion of the inner and outer nuclear membranes. They permit bidirectional transport of RNA and proteins between the nucleus and cytoplasm. Statement IV is incorrect because mRNA exits the nucleus through nuclear pores.
Question 63 of 100
📘 CLASS XI
Which statements about nucleolus are correct?
I. Spherical structure present in nucleoplasm. II. Content is continuous with nucleoplasm as it is not membrane-bound. III. Site for active ribosomal RNA (rRNA) synthesis. IV. Cells actively synthesizing proteins have larger and more numerous nucleoli.
Which statements are correct?
The nucleolus is a spherical, non-membrane-bound structure within the nucleoplasm. It is the site of active rRNA synthesis, and cells actively engaged in protein synthesis possess larger and more numerous nucleoli.
Question 64 of 100
📘 CLASS XI
Read statements regarding human genome packaging:
I. Single human cell has approximately 2 metres of DNA. II. DNA is distributed among 46 (23 pairs) chromosomes. III. Chromosomes are visible in non-dividing interphase cells. IV. Kinetochores are disc-shaped structures on centromere sides.
Which options are correct?
A human cell contains about 2 metres of DNA distributed among 46 chromosomes. Kinetochores are disc-shaped structures located on either side of the centromere. Statement III is incorrect because distinct chromosomes are visible only during cell division, whereas chromatin remains dispersed during interphase.
Question 65 of 100
📘 CLASS XI
Match the chromosome types with centromere positions:
I. Metacentric — centromere in middle, equal arms. II. Sub-metacentric — centromere slightly off-center, one shorter and one longer arm. III. Acrocentric — centromere near end, one extremely short and one very long arm. IV. Telocentric — terminal centromere.
Which statements are correct?
Metacentric, submetacentric, acrocentric, and telocentric chromosomes are correctly classified based on the position of the centromere. Therefore, all four statements are correct.
I. Non-staining secondary constriction present at constant location. II. Gives appearance of a small fragment called satellite. III. Present on all 46 human chromosomes without exception. IV. Secondary constriction alters position during every cell cycle.
Which statements are correct?
Satellite chromosomes possess a non-staining secondary constriction at a constant position, producing a small segment called a satellite. Statement III is incorrect because only a few chromosomes possess satellites, and Statement IV is incorrect because the secondary constriction remains at a constant location.
Question 67 of 100
📘 CLASS XI
Select the correct statements regarding microbodies:
I. Minute, membrane-bound vesicles. II. Contain various enzymes. III. Present in both plant and animal cells. IV. Non-membranous nuclear inclusions.
Which statements are correct?
Microbodies are minute membrane-bound vesicles containing various enzymes and are present in both plant and animal cells. Statement IV is incorrect because microbodies are membrane-bound cytoplasmic organelles, not non-membranous nuclear inclusions.
Question 68 of 100
📘 CLASS XI
Read the statements regarding G.N. Ramachandran:
I. Founder of the Madras school of conformational analysis of biopolymers. II. Discovered the triple helical structure of collagen published in 1954. III. Developed the Ramachandran plot for allowed protein conformations. IV. Influenced by Linus Pauling's work on α-helix and β-sheet.
Which statement combination is correct?
G.N. Ramachandran founded the Madras school of conformational analysis, proposed the triple helical structure of collagen in 1954, developed the Ramachandran plot, and was inspired by Linus Pauling's work on protein structure.
I. Physico-chemical approach to study living organisms. II. Uses cell-free systems to investigate physiological processes in molecular terms. III. Applies concepts and techniques of physics and chemistry to biology. IV. Rejects molecular basis of living phenomena completely.
Which statements are correct?
Reductionist biology applies physico-chemical concepts and cell-free systems to understand biological processes at the molecular level. Statement IV is incorrect because reductionist biology explains, rather than rejects, the molecular basis of life.
Question 70 of 100
📘 CLASS XI
Which statements about cell discovery are correct?
I. Robert Hooke discovered live cells. II. Antonie Von Leeuwenhoek first saw live cells. III. Robert Brown discovered the nucleus in 1831. IV. Flemming named the nuclear material chromatin.
Which statements are correct?
Antonie Von Leeuwenhoek first observed live cells. Robert Brown discovered the nucleus in 1831, and Flemming named the stained nuclear material chromatin. Statement I is incorrect because Robert Hooke observed dead cork cells.
