Which of the following are enucleated cells? A. RBC of frog B. Sieve tube element C. RBC of crocodile D. Both A and B
Hint: Nucleus is called the heart of the cell. It controls all the functioning of the cell. Enucleated cells are the cells which do not have a nucleus. The enucleated cells are deprived of genetic material. They do not have the capacity of cell division. Adult human RBCs are enucleated.
Complete Answer: The cell without a nucleus is called an enucleated cell. Adult human RBC do not have nuclei so that they can transport oxygen.
(i) RBC of frog- The frogs have nucleated RBC. All the non-mammalian vertebrates have nucleated RBC. The nucleus of the frog contains DNA as well. (ii) Sieve tube element- Sieve tube elements are the component of the Phloem in plants. They have sieve like pores at the transverse end wall. The phloem is responsible for the conduction of food in the plants. The nuclei of the sieve tube elements have fragmented and eventually disappeared. So these cells are enucleated. (iii) RBC of crocodile- Crocodile does not have RBC and haemoglobin.
The correct answer is (B). Sieve tube element is enucleated.
Additional information: Definite nucleus is the characteristic of eukaryotic cells. The eukaryotic nucleus is enclosed with a nuclear membrane which protects it and separates it from cytoplasm. In prokaryotes, all the envelope bound organelles are absent. The nucleus is naked without any membrane. The genetic material is suspended in the cytoplasm.
Note: The major conducting cells in the phloem are the sieve tube cells. They become enucleated at maturity just like human RBC. These cells can no longer divide and the lifespan is also very limited. They are able to transport sugars over long distances in the plant.