The two strands of the double helix are anti-parallel, which means that they run in opposite directions. The backbone of a double helix is made of sugar-phosphate. The backbone can be thought of as the sides of a ladder, whereas the bases in the middle form the steps; also known as rungs of the ladder. Each rung is composed of two base pairs, either an adenine-thymine pair that form a two-hydrogen bond together, or a cytosine-guanine pair that form a three-hydrogen bond. The base pairing is thus restricted. This restriction is essential when the DNA is being copied. When DNA-helix is spread out in two long stretches of sugar-phosphate backbone with a line of free bases sticking up from it. Each half will then be the template for a new, complementary strand. Biological machines inside the cell put the corresponding free bases onto the split molecule and also "proof-read" the result to find and correct any mistakes. After the doubling, this gives rise to two exact copies of the original DNA molecule. The coding regions in the DNA strand, the genes, make up only a fraction of the total amount of DNA. The DNA stretches that flank the coding regions are called introns, and consist of non-coding DNA. Today, biologists and geneticists believe that this non-coding, also known as introns; in DNA may be essential in order to expose the coding regions and to regulate how the genes are expressed.
1. What is the backbone of the double helix made of?
2. What is essential when the DNA is being copied?
3. What are introns essential for in DNA?
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1. The backbone of the double helix is made of sugar phosphate.
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3. In order to expose the coding regions & to regulate how the genes are expressed.