Chapter 15 How Genes Work
15.1 What Do Genes Do?
Knockout mutants/null mutants/loss-of-function mutants: Alleles that do not function at all.
One-gene, one-enzyme hypothesis: Genes contain the information needed to make proteins,
many of which function as enzymes.
Genetic screen: Technique for picking certain types of mutants out of many thousands of
randomly generated mutants.
*Figure 15.2 Experimental support for the one-gene, one-enzyme hypothesis.
15.2 The Central Dogma of Molecular Biology
-Crick’s idea was that different combinations of bases could specify the 20 amino acids.
DNAas the Intermediary between Genes and Proteins
-Jacob and Monod predicted that mRNA carry information from DNAto the site of protein
-RNApolymerase synthesizes RNAmolecules according to the information provided by the
sequence of bases in a particular stretch of DNA. Does not require primer.
Question: How is information transferred from DNAto RNA?
Hypothesis: RNAis synthesized by complementary base pairing with DNA.
Null hypothesis: RNAis not synthesized by complementary base pairing with DNA.
Experimental setup: Reaction mix using: 1. Ribonucleotides (A,U,C,G) 2. RNApolymerase 3.
DNAstrand with thymine as the only base.
Prediction:An RNAstrand will be produced containing only adenine.
Prediction of null hypothesis: No RNAstrand will be produced, or an RNAstrand with a
random assortment of bases will be produced.
Results: RNAstrand with adenine as the only base.
Conclusion: Information is transferred from DNAto RNAvia complementary base-pairing.
The Central Dogma Francis Crick: DNAcodes for RNAwhich codes for protein. DNA RNA protein
DNA is the hereditary material. Genes consist of specific stretches of DNA that code for products
used in the cell. The sequen