Look at these images, the oldest is at the bottom, the newest is at the top, so the drawings are next to time zones are properly set up, so next to the time scale is when the drawing next to it was made.
The DNA (deoxyribonucleic acid) is the double helical in structure. It has two anti parallel strands of long polynucleotides. The nucleotides are two purines ( adenine and guanine) and two pyrimidines ( thymine and cytosine). These purines and pyrimidines are attached with their complementary. Adenine pairs with the thymine with the two hydrogen bonds and the guanine pair with cytosine by three hydrogen bonds. The two strands are twisted which is responsible for the helical structure. The overall charge on the DNA molecule is the negative charge.
A control group is important for an experiment because it allows the experiment to minimize the changes in all other variables except the one being tested.
