Question

8. The effect of _________ on embryonic development is ___________.

A. polyspermy, the embryo develops normally but is twice as large

B. polyspermy, disruptive cell divisions and the early death of the embryo

C. polyandry, disruptive cell divisions and the early death of the embryo

D. mitosis, disruptive cell divisions and the early death of the embryo

Answer 1

The correct option is (B).

The effect of polyspermy on embryonic development is disruptive cell divisions and the early death of the embryo.

Polyspermy describes an egg that has been fertilized by more than one sperm.Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy, on the other hand, contains three or more copies of each chromosome—one from the egg and one each from multiple sperm. Usually, the result is an inviable zygote. This may occur because sperm are too efficient at reaching and fertilizing eggs due to the selective pressures of sperm competition. Such a situation is often deleterious to the female: in other words, the male-male competitionamong sperm spills over to create sexual conflict.

Polyspermy is very rare in human reproduction. The decline in the numbers of sperm that swim to the oviduct is one of two ways that prevents polyspermy in humans. The other mechanism is the blocking of sperm in the fertilized egg. According to Developmental Biology Interactive, if an egg becomes fertilized by multiple sperm, the embryo will then gain various paternal centrioles. When this happens, there is a struggle for extra chromosomes. This competition causes disarrayment in cleavage furrow formation and the normal consequence is death of the zygote.. Only two cases of human polyspermy leading to birth of children have been reported.

Polyspermy

Sperm Corona radinta Zona pellucida First polar body Oocyte in second meiotic reaction Granulosa cells of corona radiata Zona pellucida Ooeyte plasmO Fusion of ooyeCortical and sperm plasma reaction membranes Certical granule Oocyte cytoplasm- Sperm nucleus engulfed by ooeyte cytoplasm