Question

Given below is a figure showing transport of ovum, fertilisation and passage of a growing embryo through the fallopian tube in a human female.

Answer the questions that follow:

1. What will be the ploidy of cells shown in the (a) and (c) stages in the figure given below?
2. What will happen if component L, as shown in the figure (g) given below, does not attach properly to the endometrium?
3. In a pregnant mother (case X), during early pregnancy, the fertilised egg splits into two embryos at stage C shown in the figure given below, resulting in the formation of twins. Will the genome of cells of these two embryos exhibit variation? Justify your answer.

Answer 1

1. Stage (a): The ovum is haploid (n).
   Stage (c): The blastomeres are diploid (2n).
2. If component L (the blastocyst) fails to attach properly to the endometrium, implantation will not occur, and the embryo will not receive nourishment, leading to failure of pregnancy (early embryonic loss).
3. No, the genomes of the two embryos will not exhibit variation because they arise from the same fertilised egg (zygote) and therefore have identical genetic material.