All Free Biology MCQs with Answers
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19844 questions · page 580 of 1985
5791. Atrial depolarization is represented by:
- A. P wave
- B. QRS Complex
- C. T wave
- D. PQRS
Explanation: The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activation that initiates the contraction of the atria. The QRS complex follows, representing ventricular depolarization, while the T wave represents ventricular repolarization. Therefore, the P wave is specifically associated with atrial depolarization. The term 'PQRS' is not a valid ECG component, thus it does not correspond to any specific physiological event in the heart.
Correct answer: P wave5792. 'Bundle of His' is a part of which organ?
- A. Brain
- B. Heart
- C. Kidney
- D. Pancreas
Explanation: The Bundle of His conducts impulses from the AV node to ventricles, ensuring synchronized contraction of the heart.
Correct answer: Heart5793. Spread of tumor cells and establishment of secondary areas of growth is called:
- A. Benign tumors
- B. Metastasis
- C. Cancer
- D. Apoptosis
Explanation: Malignant tumor calls divide rapidly, invade nearby tissues, and enter blood or lymph, forming secondary growths this process is metastasis.
Correct answer: Metastasis5794. Pick up the longest phase of meiosis I:
- A. Metaphase I
- B. Prophase I
- C. Anaphase II
- D. Telophase I
Explanation: Prophase I is longest due to homologous chromosome pairing (synapsis) and crossing over, consisting of leptotene, zygotena, pachytene, diplotene, diakinesis.
Correct answer: Prophase I5795. _ may last for days, weeks, or even years:
- A. Zygotene
- B. Leptotene
- C. Pachytene
- D. Diplotene
Explanation: Diplotene stage can last very long (especially in oocytes), with homologous chromosomes remaining attached at chiasmata.
Correct answer: Pachytene5796. Cytokinesis refers to the division of:
- A. Nucleus
- B. Whole cell
- C. Cytoplasm
- D. Mitochondria
Explanation: The Cytokinesis divides the cytoplasm, producing two daughter cells after nuclear division.
Correct answer: Cytoplasm5797. In the human cell cycle, the S-phase lasts for:
- A. 30 minutes
- B. 10 hours
- C. 9 hours
- D. 4.5 hours
Explanation: The S-phase, during which DNA replicates, lasts-9 hours. G1-10 hrs, G2-4 hrs, M-1 hr.
Correct answer: 9 hours5798. Which one of the following is absent in animal cells?
- A. Spindle
- B. Chromatids
- C. Centriole
- D. Phragmoplast
Explanation: This Phragmoplast guides cell plate formation during cytokinesis in plants; animal cells lack it and form cleavage furrows instead.
Correct answer: Phragmoplast5799. The spindle fibers are composed of RNA and protein called:
- A. Myoglobin
- B. Actin
- C. Tubulin
- D. Myosin
Explanation: Spindle fibers are microtubules made of 𝜶-and β-tubulin proteins; they do not contain RNA.
Correct answer: Tubulin5800. The condensation of chromosomes reaches its maximum at:
- A. Leptotene
- B. Pachytene
- C. Zygotene
- D. Diakinesis
Explanation: In diakinesis, chromosomes are maximally condensed and homologous chromosomes begin separating at chiasmata.
Correct answer: Diakinesis