All Free Biology MCQs with Answers
Every Biology question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
19844 questions · page 682 of 1985
6811. The number of nuclear pores in the nuclei of differentiated cells such as erythrocytes is only:
- A. 1-2 nuclear pores/nucleus
- B. 2-3 nuclear pores/nucleus
- C. 3-4 nuclear pores/nucleus
- D. 5-6 nuclear pores/nucleus
Explanation: A differentiated cell which have been assigned a specific role and is not destined to divide further is less active metabolically and need less guidance from chromosomes and genes. Thus have less nuclear pores for communication with nucleus.
Correct answer: 3-4 nuclear pores/nucleus6812. The example of undifferenfiated cells is that of:
- A. Leucocytes
- B. Erythrocytes
- C. Osteocytes
- D. Egg cells
Explanation: Egg cell is an undifferentiated cell which undergoes repeated mitoses after fertilization for development and remains highly active. That is why it needs much communication with nucleus and as a result much number of nuclear pores. i.e. upto 30,000 per nucleus.
Correct answer: Egg cells6813. Number of nucleoli may be:
- A. Many per nucleus
- B. One per nucleus
- C. One or more per nucleus
- D. Zero per nucleus
Explanation: Number of nucleoli varies in different types of diploid cells, minimum being one and maximum may be in thousands. It depends upon the activeness of cell.
Correct answer: One or more per nucleus6814. It is the place where ribosomes are assembled and then exported to the cytoplasm via nuclear pores.
- A. Nucleus
- B. Nucleoplasm
- C. Nuclear envelope
- D. Nucleolus
Explanation: Nucleoli are factories of ribosome synthesis whereas, ribosomes are factories of protein synthesis. Ribosomes are synthesized and assembled in nucleoli, then ribosomes synthesize proteins.
Correct answer: Nucleolus6815. During cell division thread like material is converted into darkly stained structures known as:
- A. Nucleoli
- B. Nuclear membrane
- C. Nucleosomes
- D. Chromosomes
Explanation: Nucleus of a non-dividing cell contain chromatin material in form of network which have been obtained by uncoiling and decondensation of chromosomes. As the cell division startsthe chromatin material is recoiled/recondensed to acquire the shape of chromosomes. Chromosomes appear as thread like structures in nucleus at that time under microscope.
Correct answer: Chromosomes6816. The place on chromosomes where spindle fibres are attached during cell division is called:
- A. Centromere
- B. Chromatid
- C. Secondary constriction
- D. Nucleosome
Explanation: Centromere or primary constriction is that part of chromosome that links sister chromatids or a dyad. During mitosis, spindle fibers are attached to centromere via the kinetochore.
Correct answer: Centromere6817. Each chromosome consists of ........ at the beginning of cell division.
- A. Two non-sister centromeres
- B. Two sister chromatids
- C. Two non-sister chromatids
- D. Two sister centromeres
Explanation: Both chromatids of same chromosome are sister to each other whereas they are non-sister to the chromatids of other homologue. During gametogenesis both sister chromatids areseparated and each goes to a separate gamete. However, in S phase of cell cycle each chromatid synthesizes its sister chromatid again.
Correct answer: Two sister chromatids6818. All the information needed to control the activities of the cell is located on the chromosomes in the form of:
- A. Centromeres
- B. Kinetochores
- C. Genes
- D. Genetic material
Explanation: Genes are physical units of heredity located on chromosomes.
Correct answer: Genes6819. The number of chromosomes in _ remains constant generation after generation.
- A. All individuals of same species
- B. All individuals of different species
- C. Few individuals of same species
- D. Few individuals of different species
Explanation: The number of chromosomes is fixed for a species and any change in it leaves drastic impact on that individual. Such individuals are usually abnormal e.g. Down's syndromewith 47 chromosomes and Turner's syndrome with 45 chromosomes.
Correct answer: All individuals of same species6820. In man each cell contains:
- A. 23 chromosomes
- B. 46 chromosomes
- C. 8 chromosomes
- D. 48 chromosomes
Explanation: It is normal diploid number of chromosomes in human being, however gametes or germ cells being haploid contain half (23) number of chromosomes
Correct answer: 46 chromosomes