Question

Given below are two statements regarding embryonic cleavage and twin formation in humans
Statement 1: Before 8 days, if the developing cells of the embryo divide into two embryos, then it makes monozygotic twins.
Statement 2: Segregation of embryo later than 8 days is likely to produce conjoined twins.
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 A Both the statements are true

Twins are two offspring from a single birth. Monozygotic twins develop from the splitting of one zygote (formed from the fertilization of the single egg ) into two separate embryos. They contain exactly the same genetic material and are of the same sex.

Normal monozygotic twins, in 99% of the cases, arise from the developing cells which separate into two embryos before 8 days of the cleavage process. If the separation of the embryos takes more than 8 days, then possibly it makes conjoined twins.

In conjoined twins, the babies born are physically connected by any part of the body. Most conjoined twins are stillborn or die shortly after birth. Non-conjoined monozygotic twins form up to day 14 of the embryogenic development, but when twinning occurs after 14 days, twins will likely be conjoined.