Final answer:
The percent of dizygotic twins that are the same sex is 50%. This is because there is a 25% chance that the twins will both be female and a 25% chance that they will both be male. The other 50% accounts for the twins being of opposite sexes.
Step-by-step explanation:
To answer the question regarding the percent of dizygotic twins that are the same sex, we can examine the basic principles of human reproduction. When two eggs are released and fertilized, resulting in dizygotic twins, each zygote has an independent chance of developing into either a male or female, following regular patterns of genetic inheritance. Since each egg is independently fertilized, the sex of each twin is determined by the combination of sex chromosomes from the mother (always an X chromosome) and the father (either an X or a Y chromosome).
In terms of probabilities, there is a 50% chance that a fertilized egg will develop into a male (XY) and a 50% chance it will develop into a female (XX). Therefore, for dizygotic twins, there is a 50% chance that both will be female (XX and XX), a 50% chance that both will be male (XY and XY), and a 50% chance that they will be of different sexes (XX and XY).
But since we have three scenarios, we need to calculate the probability of having twins of the same sex. This is worked out as 25% chance both will be female plus 25% chance both will be male, giving us a total probability of 50% that dizygotic twins will be of the same sex.