A couple has twins. One is a boy and one is a girl. How do you know what
kind of twins they are?
O
A. They are identical twins, because they have the same parents.
O
B. They are fraternal twins, because they have the same parents.
C. They are identical twins, because they were born at the same time.
O
O
D. They are fraternal twins, because they do not have the same DNA.
SUBMIT

D. They are fraternal twins, because they do not have the same DNA.

Explanation: Identical twins are twins formed from a zygote. When an ovum (egg) is fertilized by a spermatozoa, a zygote is formed. The zygote undergoes division which results in the formation of two embryos which ultimately develop into two identical offsprings. Usually identical twins are of the same type of sex because they developed from one egg and one sperm cell and have the same DNA. Identical twins are also called homozygous twins.

On the other hand, fraternal twins are formed by the fertilization of different ova (eggs) by different sperm cells. Two different eggs are fertilized by two different sperm cells resulting in two different individuals with different genetic makeup. Fraternal twins are also called heterozygous twins. Fraternal twins can be of the same sex or different sexes but they are not identical because they do not have the same DNA.

the answer is a or when it says crossing over

✿   this landform has a high elevation and a high relief

✿   this landform is a mountain