OCR AS Biology- Nucleic Acid

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2.1.2 Nucleic Acid

a) DNA stands for Deoxyribonucleic Acid. It is a double stranded polynucleotide made up the nucleotides adenine, thymine, cytosine and guanine.

b) RNA stands for Ribonucleic Acid. It is a single stranded polynucleotide made up of the nucleotides adenine, uracil, cytosine and guanine.

c) Between the adenine and thymine there are two hydrogen bonds. Cytosine and guanine on the other hand contain three hydrogen bonds between them. The two antiparallel strands lie next to each other but go opposite ways. When these two strands are joined together it forms one molecule of DNA.

d) DNA helicase causes the DNA strand to unwind and DNA polymerase causes the two strands to split. Once they have split, free nucleotides join together with complementary base pairing. This then creates a sugar-phosphate back bone joining the deoxyribose and phosphate heads together.

e) a gene is a short sequence of DNA that codes for one protein.

f) DNA and RNA are used to code for proteins or genes. They are also used to create primary structure.