Question

The mechanism of fertilisation involves different events like approximation of gametes, acrosomal reaction activation of egg and amphimixis. According to F.R. Lillie approximation occurs due to interacting complementary substances called as fertilizin and anti fertilizin.

During amphimixis many events occur. Choose the incorrect event from the following events.

A. Swelling of the sperm nucleus

B. Initial movement of the male pronucleus along the copulation path

C. Establishment of achromatic spindle by the proximal centriole

D. Completion of second meiotic division if it has not occurred already.

Answer 1

Amphimixis is sexual reproduction where there is fusion of two male gametes to form zygote and this F. R. Lillie theory is based on Sea urchin where chemicals released by ova are fertilized.

Complete answer:

First of all, you should know about the F. R. Lillie fertilization theory. This theory was proposed in 1917 by F. R. Lillie and this theory is based on Sea urchin. This theory states that there is a chemical released by ovum which is called fertilizin and there is sperm on its surface which is called antifertilizin. Fertilizin is composed of glycoprotein. There is interaction between the same species of fertilizin of egg and antifertilizin of the sperm and due to this interaction, the sperms stick to the surface of egg. This sticking of sperm to the egg by chemical recognition is called agglutination.

In this theory, he showed that there is no copulation path from where the male pronucleus will move on as sperm do not enter into the egg by simple mechanical boring but there is presence of sperm cells on the part of egg due to which there is absorption of the sperm into the egg.

If we look at options now, Option A is Swelling of the sperm nucleus. This even is correct in this theory and hence it cannot be the correct option as we need to choose the incorrect event. So, it gets eliminated.

Moving to option B which is Initial movement of the male pronucleus along the copulation path. It is the correct option since there is no copulation path for the movement of the pronucleus and hence this is the correct option.

Moving to option C which is Establishment of achromatic spindle by the proximal centriole. This option is incorrect as this event is seen in this theory during amphimixis and from the question we need to choose the incorrect option. Therefore, it gets eliminated.

Last option D is Completion of the second meiotic division if it has not occurred already. This option is also incorrect since this event also occurs and hence it gets eliminated as we need to choose the incorrect event and this is the correct one.

Thus, the correct answer is option B which is Initial movement of the male pronucleus along the copulation path.

Note: According to this theory, there is a chemical which is released by ovum is fertilizin and by sperm is antifertilizin. So, there is interaction between both of these and there is agglutination seen as the sperm adhere to the egg of the same species due to this chemical recognition but there's no copulation path for male pronucleus during the time of amphimixis.