Question

One thousand pairs of twins attended a twin convention. Eight hundred pairs of these twins were of like sexes (male /male and female/female). The remaining two hundred pairs were of unlike sexes (male /female). What percentage of these twins is monozygote and what percentage is dizygote?

Answer 1

monozygotic-(800÷1000)×100= 80%

dizygotic- (200÷1000)×100 = 20%

hope it helps!

Answer 2

1.Monozygotic twins :- are always of the same sex because they originates from the same Fertilized egg and Fertilized by the same sperm,so they share the same DNA.The zygote contains either male (XY) or female (XX) sex Chromosomes.
2.Dizygotic twins originate from two eggs and separately Fertilized by two sperms, therefore they don't share the same DNA.
3.Now comes to the question:-
Out of 1000 twins:-
1.800 twins are like sexes (either XY male twins or XX female twins ) so they are monozygotic twins.
2.Out of 1000 :- 200 twins are of unlike sexes,so they are dizygotic twins.
Therefore:-
1.Percentage of monozygotic twins is 800/1000 x 100 =80% and
2.Percentage of Dizygotic twins is
200/1000 X 100 =20%
Hope it helps.