AQA · Biology · 8461
GCSE Biology: DNA structure
Inheritance, variation and evolution · AQA GCSE Biology (8461), specification point 4.6.1.5. Cards are generated from the exam board's own specification for "DNA structure", and every card links back to the page it came from. Separate science only. Specification © AQA — used with attribution.
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How many different nucleotides make up the DNA polymer?
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Four — one for each of the bases A, C, G and T.
What are the three components of a DNA nucleotide?
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A sugar, a phosphate group, and one of four bases attached to the sugar.
A sequence of ? bases in DNA codes for a particular amino acid.
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three
What determines the order in which amino acids are assembled into a protein?
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The order of bases in the DNA.
What makes up the backbone of a DNA strand?
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Alternating sugar and phosphate sections, with a base attached to each sugar.
In complementary DNA strands, C always pairs with ? on the opposite strand.
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G
In complementary DNA strands, T always pairs with ? on the opposite strand.
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A
Where in the cell are proteins synthesised?
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On ribosomes, according to a template.
What role do carrier molecules play in protein synthesis?
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They bring specific amino acids to the ribosome to add to the growing protein chain in the correct order.
Why does a completed protein chain fold into a unique shape?
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The unique shape enables it to do its job — as an enzyme, hormone or structural protein such as collagen.
What effect do most mutations have on the protein produced?
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Most do not alter the protein, or alter it only slightly so its appearance or function is unchanged.
How can a mutation stop an enzyme from working?
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It can code for a protein with a different shape, so the substrate no longer fits the enzyme's binding site.
What is the function of non-coding parts of DNA?
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They can switch genes on and off, so variations there affect how genes are expressed.
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