Warm-Up Explain how a secondary messenger is activated, and how this affects gene expression. (LO 3.22)
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The first cell on Earth (approx. 3.5 billion years ago) was simple and prokaryotic, consisting of DNA, a membrane, and ribosomes. The First Cell (artist interpretation)
The first cell on Earth (approx. 3.5 billion years ago) was simple and prokaryotic, consisting of DNA, a membrane, and ribosomes. Eukaryotic cells, which evolved later, are larger and contain internal membranes called organelles.
THE FIRST CELL Prokaryotic Gene Regulation The first cell on Earth (approx. 3.5 billion years ago) was simple and prokaryotic, consisting of DNA, a membrane, and ribosomes. Eukaryotic cells, which evolved later, are larger and contain internal membranes called organelles. Prokaryotic (all unicellular) and eukaryotic (uni- and multicellular) organisms exist today and have their own forms of gene regulation (eukaryotic was yesterday; prokaryotic is today). eukaryotes prokaryotes
3B.1b: Both positive and negative control mechanisms regulate gene expression in bacteria (prokaryotes) and viruses. 3B.1b.1: The expression of specific genes can be turned on by the presence of an inducer. 3B.1b.2: The expression of specific genes can be inhibited by the presence of a repressor. 3B.1b.3: Inducers and repressors are small molecules that interact with regulatory proteins and/or regulatory sequences. 3B.1b.4: Regulatory proteins inhibit gene expression by binding to DNA and blocking transcription (negative control). 3B.1b.5: Regulatory proteins stimulate gene expression by binding to DNA and stimulating transcription (positive control) or binding to repressors to inactivate repressor function. 3B.1b.6: Certain genes are continuously expressed; that is, they are always turned on, e.g., the ribosomal genes. 4C.2a: Environmental factors influence many traits both directly and indirectly. Illustrative examples: Effect of adding lactose to a Lac + bacterial culture
Prokaryotic genes are organized into operons, or sequences of genes and the genes of their transcriptional repressors. Ex: The lac operon encodes laci and lacz.
Prokaryotic genes are organized into operons, or sequences of genes and the genes of their transcriptional repressors. Ex: The lac operon encodes laci and lacz. laci encodes the transcriptional repressor of lacz. lacz encodes B-Gal, an enzyme that breaks down lactose.
Prokaryotic genes are organized into operons, or sequences of genes and the genes of their transcriptional repressors. Ex: The lac operon encodes laci and lacz. laci encodes the transcriptional repressor of lacz. lacz encodes B-Gal, an enzyme that breaks down lactose. No lacz RNA made!
Prokaryotic genes are organized into operons, or sequences of genes and the genes of their transcriptional repressors. Ex: The lac operon encodes laci and lacz. laci encodes the transcriptional repressor of lacz. lacz encodes B-Gal, an enzyme that breaks down lactose. Negative control: lacz expression is prevented by the LacI repressor. No lacz RNA made!
Prokaryotic genes are organized into operons, or sequences of genes and the genes of their transcriptional repressors. Ex: The lac operon encodes laci and lacz. laci encodes the transcriptional repressor of lacz. Negative control: lacz expression is prevented by the LacI repressor. lacz encodes B-Gal, an enzyme that breaks down lactose. Positive control: LacI repressor is inhibited by an inducer (represses the repressor).
laci encodes the transcriptional repressor of lacz. Negative control: lacz expression is prevented by the LacI repressor. lacz encodes B-Gal, an enzyme that breaks down lactose. Positive control: LacI repressor is inhibited by an inducer (represses the repressor). This is a feedback loop because lactose is the inducer! lactose is the B- Gal inducer! B-Gal breaks down lactose Extremely boring video
CTQ #1 Explain the difference between prokaryotic and eukaryotic organisms. Why do prokaryotic organisms not have different cell types, while most eukaryotic organisms do?
CTQ #2 Describe using a representation (illustration, diagram, et cetera) a positive control and a negative control of the lac operon in a bacterial cell. (LO 3.23)
Closure Explain how environmental factors can influence the phenotype of a bacterial cell. (LO 4.23)