Chapter 7

Gene Expression and Regulation

• The Blueprint of Life refers to DNA, which contains the genetic instructions for an organism.

About Nester's Microbiology

• The title of Chapter 7 in Nester's Microbiology is "Genetics and Gene Regulation".
• The authors of Nester's Microbiology are not specified.
• The edition of Nester's Microbiology is not specified.
• The organization that holds the rights to Nester's Microbiology is not specified.

Transcription

• RNA synthesis occurs in the 5' → 3' direction.
• The enzyme that synthesizes single-stranded RNA using DNA as a template is RNA polymerase.
• The strand of DNA that serves as the template for RNA synthesis is the template strand.
• The role of a promoter in transcription is to provide a binding site for RNA polymerase.
• When RNA polymerase encounters a terminator sequence, transcription is terminated.
• RNA is usually shorter and synthesized from a DNA template strand.

Central Dogma

• The central dogma of molecular biology is the process by which genetic information flows from DNA to RNA to proteins.

DNA Structure

• The process by which DNA forms a double-stranded helix is called DNA replication.

Genes and Gene Expression

• The functional unit of heredity that encodes gene products, usually proteins, is a gene.
• George Beadle and Edward Tatum concluded that "one gene, one enzyme" based on their experiments with mold.
• In eukaryotic gene expression, the expression of genes is more complex and regulated at multiple levels.

Signal Transduction and Natural Selection

• The purpose of signal transduction in cells is to transmit signals from the environment to the nucleus to regulate gene expression.
• The role of natural selection in gene expression is to favor the expression of genes that confer a survival advantage.

Bacterial Gene Regulation

• An operon in bacterial gene regulation is a cluster of genes transcribed together into a single mRNA molecule.
• The purpose of inducible enzymes in bacterial gene regulation is to allow bacteria to adapt to changes in their environment.

The Genetic Code

• The genetic code is a set of rules that dictates how nucleotide sequences are translated into amino acid sequences.
• The genetic code is degenerate, meaning that more than one codon can code for the same amino acid.

Translation

• The role of mRNA in translation is to carry the genetic information from DNA to the ribosome.
• The role of ribosomes in translation is to read the mRNA sequence and assemble the corresponding amino acids into a polypeptide chain.
• The function of transfer RNA (tRNA) in translation is to bring amino acids to the ribosome during protein synthesis.
• During the elongation phase of translation, amino acids are added to the growing polypeptide chain.

Regulatory Mechanisms

• The two most common regulatory mechanisms to control transcription are repression and activation.
• The role of repressors in transcriptional regulation is to bind to operators and prevent RNA polymerase from transcribing the adjacent genes.
• The role of activators in transcriptional regulation is to bind to enhancers and increase the transcription of adjacent genes.
• The lac operon is turned on in the absence of glucose and the presence of lactose.
• Carbon catabolite repression (CCR) in the lac operon is a mechanism that prevents the expression of the lac operon in the presence of glucose.