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Genetics, Stem Cell Research and Cloning

RNA, genes and the triplet code

  • 3 things to know
  • A2 5

Overview

RNA against DNA, messenger, transfer and ribosomal RNA, genes, loci and polypeptides, the triplet code with a worked base count, mutations and new alleles, substitutions and frameshift deletions.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Why might a base substitution leave a polypeptide unchanged, while a single-base deletion is usually harmful?

Key term

How does the structure of RNA differ from that of DNA?

Key term

What is messenger RNA, and what does it do?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    How does the structure of RNA differ from that of DNA?

    Model answer

    RNA is usually a single, shorter strand containing the sugar ribose. RNA has the base uracil in place of thymine.

  2. 2

    What is messenger RNA, and what does it do?

    Model answer

    Messenger RNA is a single-stranded copy of a gene made during transcription in the nucleus. The mRNA carries the code to the ribosomes as a series of three-base codons.

  3. 3

    Describe the structure and role of transfer RNA.

    Model answer

    Transfer RNA is a short strand folded into a clover-leaf shape with an anticodon of three bases. A specific amino acid attaches at one end and is carried to the ribosome.

  4. 4

    What is the role of ribosomal RNA?

    Model answer

    Ribosomal RNA combines with proteins to form ribosomes. A ribosome holds the mRNA and tRNA in place while amino acids are joined in translation.

  5. 5

    What is a gene?

    Model answer

    A gene is a section of DNA with a specific sequence of bases. The sequence carries the code for a particular polypeptide.

  6. 6

    What is a polypeptide, and how does it relate to a protein?

    Model answer

    A polypeptide is a chain of amino acids joined by peptide bonds. A protein is made of one or more polypeptides folded into a particular shape.

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