Question

The nucleus is absent in the mature
a. Sieve tube cells
b. Mammalian erythrocytes
c. Monocytes
d. Both A and B

Answer 1

Hint: The nucleus is the cell organelle of the eukaryotic cell that contains DNA. It is known as the genetic material of a cell. The nucleus also contains different varieties of proteins to form chromosomes. It is a membrane-bound organelle that maintains the integrity of the cell.

Complete answer:
the nucleus is absent in mature sieve tube cells and mammalian erythrocytes. Sieve tube is described as the cells of the phloem tissue present in vascular plants. Their function is to translocate and distribute the food material to different parts of the plants. The nucleus of the sieve tube fragmented and disappeared.

On the other side, the mammalian erythrocytes are also known as red blood cells and a major component of the blood. They are formed in the bone marrow. During the process of formation of erythrocytes, the nucleus and mitochondria disappear and are converted to the mature erythrocyte. They possess a red coloured pigment which is known as haemoglobin. Erythrocytes are unable to multiply because they lack a nucleus, and they can survive for 100-120 days.

Hence, the correct answer is option (D).

Note: Blood contains the blood cells, which are called the formed elements, and a fluid portion known as plasma. There are three types of blood cells present: red blood cells (erythrocytes), white blood cells(leucocytes), platelets. Plasma approximately contains 90 to 91% of water and 8% of solids. The red colour of red blood cells is derived from haemoglobin. The count of red blood cells ranges from 4.1 to 7.2 million cells per microliter. RBC count increases when we do vigorous exercise.