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The table shows that 20% of the bases in a section of double-stranded DNA are adenine (A) - HSC - SSCE Biology - Question 20 - 2007 - Paper 1
Question 20
The table shows that 20% of the bases in a section of double-stranded DNA are adenine (A). Complete the table below by identifying the other base types and calculat... show full transcript
Worked Solution & Example Answer:The table shows that 20% of the bases in a section of double-stranded DNA are adenine (A) - HSC - SSCE Biology - Question 20 - 2007 - Paper 1
Step 1
Identify the other base types
Answer
In DNA, besides adenine (A), the other three bases are thymine (T), cytosine (C), and guanine (G). Given that adenine makes up 20% of the bases, thymine will also have 20% as adenine pairs with thymine. The remaining bases—cytosine and guanine—should each account for 30% of the total bases since they are complementary pairs as well. Thus:
- A: 20%
- T: 20%
- C: 30%
- G: 30%
Step 2
Construct a simple flowchart to describe the process of DNA replication
Answer
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Initiation: The DNA double helix unwinds, and the hydrogen bonds between bases break, facilitated by the enzyme helicase.
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Priming: RNA primers are laid down by primase to initiate synthesis.
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Elongation: DNA polymerase adds nucleotides complementary to the template strand, synthesizing the new strands in a 5' to 3' direction.
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Termination: Once a complete strand is synthesized, the RNA primers are replaced with DNA. The newly formed strands rewind to form a double helix.
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Result: Two identical double-stranded DNA molecules are produced.