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Answer either A or B in the space below - Scottish Highers Human Biology - Question 12 - 2017
Question 12
Answer either A or B in the space below. Labelled diagrams may be used where appropriate. A Describe the structure of DNA and the process of DNA replication. OR B De... show full transcript
Worked Solution & Example Answer:Answer either A or B in the space below - Scottish Highers Human Biology - Question 12 - 2017
Step 1
Describe the structure of DNA
Answer
DNA, or deoxyribonucleic acid, is composed of nucleotides containing deoxyribose sugar, phosphate, and a base. Each nucleotide consists of a sugar-phosphate backbone where:
- The four nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G).
- Cytosine pairs with guanine and adenine pairs with thymine through hydrogen bonds.
- The two strands of DNA are anti-parallel and run in opposite directions, specifically from 5' to 3'.
- The overall structure of DNA is that of a double helix, where two strands twist around each other.
Step 2
Describe the process of DNA replication
Answer
DNA replication occurs in several key steps:
- The DNA double helix is unwound by helicase, which separates the two strands.
- A primer is synthesized to start the replication process by attaching to the DNA strand.
- DNA polymerase then adds nucleotides to the 3' end of the new growing strand (primer).
- One strand is replicated continuously (leading strand) while the other strand is replicated in fragments (lagging strand).
- The fragments on the lagging strand are joined together by the enzyme ligase.