Grade 12 · CAPS

Grade 12 DNA: The Code of Life

Life Sciences practice questions and a worked example

Grade 12 DNA: The Code of Life covers the structure of DNA and RNA, DNA replication, protein synthesis and DNA profiling. The questions here ask you to label a DNA or RNA diagram, describe replication, transcription and translation step by step, use a codon table to work out amino acids, and read DNA profiles from a crime scene or a family. They come from the NSC Paper 2 for November 2023, 2024 and 2025: multiple-choice and terminology items from Section A and diagram, data and passage questions from Section B, each with the marking guideline's answer.

Worked example

2.2 Describe the process of DNA replication.

Answer & explanation

- The (DNA) double helix unwinds and - unzips/hydrogen bonds break - to form two separate strands - Both (DNA) strands serve as templates - to build a complementary (DNA) strand/ A pairs with T and C pairs with G - using free (DNA) nucleotides from the nucleoplasm - This results in two identical (DNA) molecules
1. The DNA double helix unwinds, allowing the two strands to separate. This is necessary for replication to begin. 2. The hydrogen bonds between the base pairs break, causing the DNA to unzip into two separate strands. 3. Each of these strands serves as a template for the formation of a new complementary strand. 4. Free DNA nucleotides in the nucleoplasm pair with the exposed bases on each template strand, following base-pairing rules: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). 5. This process results in the formation of two identical DNA molecules, each containing one original and one new strand.

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DNA: The Code of Life

Question 1 of 3

1.1.1 The base pairing in DNA was discovered by …
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More practice questions

Explore additional Grade 12 DNA: The Code of Life questions.

  • 2
    1.2 Give the correct biological term for the following description. 1.2.3 The natural shape of a DNA molecule
  • 3
    1.2 Give the correct biological term for the following description. 1.2.4 The type of bond found between two amino acids
  • 4
    1.2 Give the correct biological term for the following description. 1.2.7 The fluid of the nucleus where free nucleotides are found
  • 5
    1.2 Give the correct biological term for the following description. 1.2.8 A tangled mass of chromosomes located within the nucleus

Common mistakes

  • Mixing up transcription and translation. Transcription makes mRNA from a DNA template in the nucleus; translation happens at the ribosome, where tRNA brings the amino acids.
  • Writing T in an RNA sequence, or U in a DNA sequence. RNA has uracil in place of thymine.
  • Leaving steps out of a "describe the process" answer. Each fact in the marking guideline earns one mark, so a six-mark answer needs six separate points.

More Grade 12 Life Sciences topics

Aligned to CAPS Grade 12 Life Sciences — DNA: The Code of Life. Curriculum source: CAPS for the FET Phase, Department of Basic Education.

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