6.2 Gene Regulation

Why was the lac operon important for scientists?

Provided understanding to how different DNA segments are used in gene regulation.

Prokaryotic operons

Prokaryotic operons have proteins that work together on the same mRNA. Genes are located one after another.

Promoters in prokaryotic operons

Informs RNA polymerase when to start transcription.

Operators in prokaryotes

On and off switch. Nucleotide sequence between promoter and structural genes in operon structure.

Regulators in prokaryotes

Gene coding for repressor protein.

Repressor in prokaryotes

Protein that binds to operator to block and stop protein synthesis

Inducible Operon

Usually turned off. Enzymes produced when substrate triggered.

Repressible operon

Usually on; enzyme production stops when product is present.

Prokaryotic Translation

Immediately occurs while mRNA is being made.

Prokaryotic operons vs eukaryotic operons controls

Controls are all consistent in prokaryotic operons, while eukaryotic operons have individual controls for each gene.

Eukaryote transcription controls

Genes are turned on and off based on cell needs. Transcription factors and activator proteins ensure a gene is used at the right time and every protein in the right amount and place.

Differential gene expression

As cells mature, multicellular organisms will express limited number of genes specific to thier function.

Embryonic cell differentiation

Embryonic cells differentiate as they mature.

Cytoplasmic Determinant

In egg’s cytoplasm, responsible for determining the fate, function, and cell structure.

Morphogenesis

Builds an organism’s structure

Induction

Interactions with other neighboring cells, chemicals, environment, and signaling molecules determine cell fate.

Pattern Formation

Organizes body plans. Positional information signals dictate where, what’ll it be, and what’ll do for a cell.

Homeotic (Hox) genes

Control pattern formation in an organism.

Morphogen Gradient

Responsible for ESTABLISHING axes

Egg Polarity Gene

Gene Responsible for determining anterior-posterior and dorsal-central axes.

Gene expression regulation

In multicellular organisms, as cells differentiate, they synthesize proteins just for their type.

All Somatic cells have…

Genes

Euchromatin

Diffuse chromatin; site where DNA transcription takes place.

Heterochromatin

Condensed chromatin; genes aren’t expressed as proteins.

The proportion of…

heterochromatins to euchromatin increases as cell specializes.

Enhancers in eukaryotes

DNA sequence that activates gene; contains control elements activators bind to.

Activators in eukaryotes

Proteins that bind to control elements in enhancer, allowing transcription of a specific gene to begin by linking to transcription factors on promoter.

Transcription factors in eukaryotes

Proteins that bind to promoter and specific activators on enhancer proteins, folding DNA to express a gene.

Introns

Useless pieces of DNA that seperate exons

Exons

Pieces/segments of DNA

Introns and Transcription

Introns are copied during transcription, but cut out shortly after