Human Reproduction Question 75
75. Which one of the following statements about morula in humans is correct?
[2010]
(a) It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA
(b) It has far less cytoplasm as well as less DNA than in an uncleaved zygote
(c) It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote
(d) It has more cytoplasm and more DNA than an uncleaved zygote
Show Answer
Answer : a
Hints & Solutions
(a) Morula is a solid ball contained within the zone pellucida. It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA. When the sperm approach the egg, they gets bind to the zona pellucida in a process known as sperm binding. This triggers the acrosome reaction, in which the enzymes of the acrosome are freed. These enzymes then begin to digest the zona pellucida and allow the sperm to tunnel toward the egg’s plasma membrane.
