Chapter 9

Gene Expression and Regulation

How Is the Information in DNA Used in a Cell?

• Most Genes Contain Information for the Synthesis of a Single Protein (but splicing!)

• RNA Intermediaries Carry the Genetic Information for Protein Synthesis

• A Comparison of DNA and RNA

• Genetic Information Is Transcribed into RNA, Then Translated into Protein

• Genetic information flows from DNA to RNA to protein

• Genetic Information Is Transcribed into RNA, then Translated into Protein

A Sequence of Three Bases Codes for an Amino Acid

How Is the Information in a Gene Transcribed into RNA?

• Transcription Begins When RNA Polymerase Binds to the Promoter of a Gene

How Is the Information in a Gene Transcribed into RNA?

• Elongation Generates a Growing Strand of RNA

How Is the Information in a Gene Transcribed into RNA?

• Transcription Stops When RNA Polymerase Reaches the Termination Signal

How Is the Information in a Gene Transcribed into RNA?

• Transcription Stops When RNA Polymerase Reaches the Termination Signal

The message altered after transcription

What Are the Functions of RNA?

• Cells synthesize three major types of RNA

• Translation is the process of protein synthesis

• Translation Begins When tRNA and mRNA Bind to a Ribosome

Mutation

Genetics:

• A change of the DNA sequence within a gene or chromosome of an organism resulting in the creation of a new character or trait not found in the parental type.

• The process by which such a change occurs in a chromosome, either through an alteration in the nucleotide sequence of the DNA coding for a gene or through a change in the physical arrangement of a chromosome.

• A mutant.

How Do Mutations Affect Gene Function?

• Mutations May Be

– Nucleotide Substitutions

– Insertions (one or more nucleotides)

– Deletions (one or more nucleotides)

• Mutations Affect Proteins in Different Ways

– Protein unchanged

– Protein equivalent

– Protein altered

– Protein destroyed

A frameshift mutation changes the amino acid sequence from the site of the mutation.

How Do Mutations Affect Gene Function?

• BUT: Mutations Are the Raw Material for Evolution

Are All Genes Expressed?

• Gene Expression Differs from

– Cell to Cell: muscle vs. blood

– Over Time: growth hormone

• Environmental Cues Influence Gene Expression

– phenology

How Is Gene Expression Regulated?

• Regulatory Proteins That Bind to Promoters Alter the Transcription of Genes

• Some Regions of Chromosomes Are Condensed and Not Normally Transcribed

• Entire Chromosomes May Be Inactivated and Not Transcribed: the X chromosome in women

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