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Modern Genetic Analysis
3. Gene Function
Key Concepts

The functions of DNA and RNA are based on base complementarity between single strands and on attachment of nucleic acidbinding proteins of various types.
Most genes code for proteins; a few code for untranslated RNAs that are functional components of the informational processing system.
In protein-coding genes, DNA is transcribed to make mRNA, which is translated to make a polypeptide chain.
Only one strand of DNA is used as a template for transcription of a given gene.
In RNA polymerization, new nucleotides are always added at the 3 end of the growing molecule.
Protein function is determined by primary amino acid sequence, which is determined by nucleotide sequence.
The mRNA is translated three nucleotides (a codon) at a time; specificity arises through complementarity of the binding between the triplet codon and the anticodon of a tRNA bearing the appropriate amino acid.
Amino acids are added at the carboxyl end of the growing polypeptide chain.
Protein function is determined by shape, size, and binding properties, and all these are determined by amino acid sequence.
Changes in DNA nucleotide sequence may result in changes of amino acid sequence, which often result in protein malfunction.
Protein malfunction is mostly recessive, sometimes dominant.

© 1999 by W. H. Freeman and Company. All rights reserved.