Question

Given below are two statements regarding embryonic cleavage in humans
Statement 1: With more and more cleavage divisions, the resultant blastomeres become smaller and smaller in embryos.
Statement 2: The consequence of rapid cell division is that the ratio of nuclear volume to cytoplasmic volume decreases.

Choose the correct option

• A. Both the statements are true
• B. Statement 1 is true but statement 2 is false
• C. Statement 1 is false and statement 2 is true
  
• D. Both the statements are false

Answer 1

The correct option is B Statement 1 is true but statement 2 is false

Cleavage is a special type of mitosis that occurs in the zygote. As the zygote moves towards the uterus through the isthmus of the oviduct, the cell keeps on dividing and forms 2, 4, 8, 16 blastomeres.
16 celled stage is called a morula. It continues to divide and transforms into blastocyst as it moves further into the uterus. The size and zona pellucida of the zygote remains unchanged and intact, new cells are formed inside the same egg cytoplasm reducing the cytoplasmic mass.
Cleavage is a rapid mitotic division of the zygote which is characterised by the absence of the growth in the original zygote. The enormous volume of the egg cytoplasm is divided into numerous small nucleated cells here. The overall size of the zygote remains the same in due course of the divisions but the number of cells is increasing inside. So the original egg cytoplasm keeps on reducing as the division progresses. The ratio of nuclear volume to cytoplasmic volume keeps on increasing in embryonic cells