Question

Imagine that one egg cell unites with one sperm cell at fertilization. Nine months later, twin brothers are born. Select all of the true statements about the DNA of these brothers.

Answer 1

There are two types of twins. In one case, fraternal twins. They can be created when two eggs are existent at the same time inside the mother, and both eggs get fertilized. Each of them grows into a separate baby in the end. The babies that grow from each do not have the same DNA because each egg and each sperm started with not the same DNA. They are basically like other siblings, but they were born at the same time. On the other hand, another type of twins are called identical twins. There is just one egg, and it is fertilized by only one sperm. Normally the fertilized egg would divide and grow to form one baby. But, sometimes once the egg gets fertilized and begins to divide, it can come apart. After it comes apart, each half can begin with dividing and begins to grow into a baby. And because the two babies came from one and the same fertilized egg, they have identical DNA. Just always remember that fraternal twins each have their own DNA, whereas identical twins share theirs.

Even if identical twins have precisely the same DNA, they aren't absolutely identical. Which is the reason why mothers can tell their identical twin babies apart. Identical have the same genotype though. They come from the same fertilized egg anyway. Moreover, identical twins aren't entirely identical since DNA is basically like a guide to building something, yet how your body chooses to build is random. This is exactly the reason why identical twins can have distinguishable fingerprints. One more huge factor why identical twins aren't definitely and entirely identical is due to the environment wherein each of them were nurtured in. Thus, basic biology states that identical twins have the same DNA.