20.4 21.3 are the correct answers
The immense amount of information stored in DNA is coded with just four base nucleotides. These four nucleotides are paired by twos to form <u>complementary </u>DNA chains.
The makeup of DNA is limited to two <u>pairs </u>of nucleotides bases. One of these pairs is a pyrimidine base whilst the other forms a purine base. The four nucleotides that will make up the entire DNA code are:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T).
A and G will pair to form the purine base, meanwhile, Cytosine pairs with Thymine to form the <em>pyrimidine base</em>. As per the entire DNA code, A will always pair with G.
Whilst C always pairs with T. This is due to the very nature of the nucleotides themselves and will not change throughout the synthesis or duplication of DNA. Therefore, to complete the complementary strand described in the assignment we must match the letter given with its corresponding base pair, using this rule of DNA.
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According to the Big Bang theory, the universe was once very dense and is now expanding.
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