Question

The absence of centrioles from higher plant cells means that during somatic cell nuclear division there is
A) No apparent organiser of mitotic spindles
B) No equatorial arrangement of chromosomes at metaphase
C) No new cell wall laid down at telophase
D) No spindle formed

Answer 1

Hint: Centrosomes are organelle usually containing two cylindrical structures called centrioles.Centrioles are paired organelles which help in cell division by organizing spindle fibers.Both the centriole in centrosome lie perpendicular to each other. They form centrosomes which are absent in plant cells and yet plant cells divide.

Complete step by step answer:
-Centrioles form centrosomes and these are known as organizing centres for microtubules. They have a structure of 9 bundles of microtubules forming one centriole.
-During the interphase, the animal cell has duplicated centrioles. When mitosis occurs, the centrioles move to the opposite sides for spindle fiber organization. Each centriole acts as one new centre for formation of spindle fibers. They radiate spindle fibers known as asters.
-Before DNA replication, the cell has two centrioles. During the cell division, they divide and form two poles for organizing the mitotic spindle fibres. The separation of centrioles is done by enzyme separase.
-In cellular organization, the centrioles have an important role in microtubules in the cytoplasm.

So, the correct answer is A, No apparent organiser of mitotic spindles.

Note:
 Although the centrioles are known as centres for mitotic spindle formation, the animal cells like oocytes have shown division in absence of centrioles too. Absence of centrioles can also show cell division.