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Understanding the Triplet Code and Gene Expression

Explore the concept of the triplet code and gene expression, including how genes code for polypeptides and the importance of the triplet code. Learn about the structure and function of enzymes and how changes in DNA bases can impact enzyme functionality.

josehenderson
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Understanding the Triplet Code and Gene Expression

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  1. The triplet code Starter A DNA molecule is 23% guanine. What percentage of each of the other bases would it contain? G = 23% C + G = 46% C = 23% A = 27% T = 27% So A + T = 54% (to make a total of 100%)

  2. Aims: • What is a gene? • How do genes code for polypeptides?

  3. A gene is a section of DNA nucleotides that codes for the sequence of amino acids that make up a particular polypeptide.

  4. Depending on the specific groups in each amino acid the polypeptide chain then forms secondary & tertiary structures

  5. The triplet code • Only 20 amino acids • Each amino acid has its own code of bases on the DNA • 3 bases code for an amino acid (triplet code) • 64 codes so some amino acid have more than one code. • In eukaryotes much of the DNA doesn’t code for amino acids – introns • Sections of DNA that code for a.a - exons • Introns found between and in genes

  6. Features of the triplet code • Few amino acids have only a single triplet code • Most have between 2-6 triplet codes each • Degenerate code • Always read in one direction • Start of a sequence is always the same triplet code – methionine • 3 triplet codes are stop codons • Code is non-overlapping and universal

  7. Understanding checkpoint An enzyme is a protein that is responsible for speeding up chemical reactions. An enzyme’s shape is crucial to it’s function. How would a change in one base result in an enzyme becoming non-functional?

  8. Aims: Explain to your partner • What is a gene? • How do genes code for polypeptides?

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