Which of the following is an example of an animal cell that lacks a nucleus in its mature form?
A. Leukocyte
B. Hepatocyte
C. Neuron
D. Erythrocyte (human RBC)
Answer: Option D
Solution (By JKExamLibrary)
Mature mammalian red blood cells (erythrocytes) lose their nucleus and other organelles during development to maximize space for hemoglobin. Thus they are anucleate. They cannot divide or repair themselves and have a lifespan of about 120 days. Neurons, leukocytes, and hepatocytes are nucleated. RBCs obtain energy through anaerobic glycolysis.
Explanation:
Bile does not contain digestive enzymes; it contains bile salts that emulsify fats, increasing surface area for lipase action. Thus, A is false, R is true.
Explanation:
Chiasmata become clearly visible during the diplotene stage of Prophase I. While the actual exchange of genetic material (crossing over) occurs during the pachytene stage, the homologous chromosomes begin to repel each other and move apart in diplotene, remaining connected only at the sites of crossing over, which appear as X-shaped chiasmata. Exam tip: Pachytene = crossing over; Diplotene = chiasmata visible.
Explanation:
The epiglottis is a leaf-shaped elastic cartilage that covers the glottis (opening of the larynx) during swallowing, directing food into the esophagus and preventing it from entering the trachea. The thyroid cartilage forms the Adam's apple, the cricoid is ring-shaped below, and arytenoids are involved in vocal cord movement.
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