12.
From DNA to Protein: Genotype to Phenotype 256
12.1
What Is the Evidence that Genes Code
for Proteins? 257
Experiments on bread mold established
that genes determine enzymes 257
One gene determines one polypeptide
258
12.2
How Does Information Flow from Genes
to Proteins? 260
RNA differs from DNA 260
Information flows in one direction
when genes are expressed 260
RNA viruses are exceptions to the
central dogma 261
12.3
How Is the Information Content in
DNA Transcribed to Produce RNA? 261
RNA polymerases share common features
262
Transcription occurs in three steps
262
The information for protein synthesis
lies in the genetic code 263
Biologists used artificial messengers
to decipher the genetic code 265
12.4 How
Is RNA Translated into Proteins? 265
Transfer RNAs carry specific amino
acids and bind to specific codons
266
Activating enzymes link the right
tRNAs and amino acids 267
The ribosome is the workbench for
translation 268
Translation takes place in three steps
268
Polysome formation increases the rate
of protein synthesis 270
12.5 What Happens
to Polypeptides after Translation?
272
Signal sequences in proteins direct
them to their cellular destinations
272
Many proteins are modified after translation
274
12.6
What Are Mutations? 274
Point mutations change single nucleotides
275
Chromosomal mutations are extensive
changes in the genetic material 276
Mutations can be spontaneous or induced
277
Mutations are the raw material of
evolution 277
