![Page 1: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/1.jpg)
Chapter 18: Regulation of Gene
Expression
![Page 2: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/2.jpg)
Reg
ula
tio
n o
f M
etab
olis
m
Shuts off
transcription
![Page 3: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/3.jpg)
Types of Feedback
• Negative feedback = body’s response is to reduce the stimulus
– Ex: regulation of body temp, blood glucose levels, trp and lac operon
• Positive feedback = body’s response is to increase the stimulus
– Ex: child birth, blood clotting, CAP regulation
![Page 4: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/4.jpg)
Control of Gene Expression
Operons – sequence of DNA that directs particular
biosynthetic pathways
Four Major Components of an Operon
• Regulatory Gene – produces a repressor protein that
prevents gene expression by blocking RNA Polymerase
• Promoter region – sequence of DNA where RNA
Polymerase attaches for transcription
• Operator region – can block action of RNA Polymerase if
region is occupied by repressor protein
• Structural gene – contain DNA sequences that code for
several related enzymes that direct production of an end
product
![Page 5: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/5.jpg)
Control of Gene Expression
To conserve energy, cells make or use proteins responsible
for certain metabolic processes only when those processes
are needed
Trp operon – enzymes make needed tryptophan
• Repressor inactivaed in response to presence of tryptophan
• Tryptophan acts as Corepressor
• “Repressible enzymes” – Usually turned on and has to be
turned off
Lac operon – enzymes used to break down lactose
• Controls breakdown of lactose
• Lactose presence needed to turn on Operon
• Allolactose inactivates the repressor at the operator site
• “Inducible enzymes” – Usually turned off and needs to be
turned on
![Page 6: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/6.jpg)
Trp Operon (low trp densities)
Promoter is the site of
RNA polymerase binding
Makes enzymes that
produce tryptophan
![Page 7: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/7.jpg)
Trp Operon (higher trp densities)
Equilibrium: Likelihood of
being in bound state
depends on trp density
Negative
regulation Corepression
![Page 8: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/8.jpg)
Lac Operon (lower lactose densities)
Active
repressor
RNA polymerase is unable
to bind to the DNA
![Page 9: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/9.jpg)
Inducer
Lac Operon (higher lactose densities)
RNA polymerase can do
transcription
Makes enzymes that break
down lactose
![Page 10: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/10.jpg)
• When glucose levels are high and lactose is high, bacteria will break down glucose first
• When glucose levels drop, then the lac operon is activated
– cAMP levels increase when glucose decreases
– Active CAP protein binds to promoter and increases the RATE of transcription
– Allolactose and moving the repressor protein are still needed and work on negative feedback
Positive Gene Regulation
![Page 11: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/11.jpg)
Positive Gene Regulation
Still need to inactivate for
transcription to occur
Increase when
glucose levels
decline
![Page 12: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/12.jpg)
• Chromatin structure
– Histone acetylation – addition of acetyl groups decreases the binding and allows transcription to occur easier
– DNA methylation – adding methyl groups to cause DNA to wind more tightly and decreases the expression of genes
• Genomic imprinting – methylation of DNA causes maternal or paternal genes to not be expressed
– Epigenetic inheritance – inheriting traits by mechanisms not directly involving nucleotide sequence
Eukaryotic Regulation at Any Stage of Protein Synthesis
![Page 13: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/13.jpg)
• http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120080/bio27.swf::Combination+of+Switches+-+the+Lac+Operon
• https://www.youtube.com/watch?v=oBwtxdI1zvk
![Page 14: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/14.jpg)
Cell differentiation
• Observable cell differentiation results from the expression of genes for tissue-specific proteins
• Induction of transcription factors during development results in sequential gene expression
![Page 15: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/15.jpg)
• Homeotic (HOX) genes – regulate developmental patterns and sequences such as location of each body part
• Embryonic induction – when one group of developing tissues directs the development of another group
• Cytoplasmic determinants – regulatory molecules that allows for the expression of different genes in different cells as they divide
![Page 16: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/16.jpg)
![Page 17: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/17.jpg)
![Page 18: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/18.jpg)
• Apoptosis – programmed cell death
– Controlled by several genes – BCL-2 family of genes is shown to cause cancers when mutated
– Morphogenesis of fingers and toes
– C. Elegans development - Video
![Page 19: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/19.jpg)
• p53 gene – protein acts as a transcription factor and when mutated it cannot activate transcription an d will not produce a protein needed to inhibit mitosis
• SRY gene – sex-determining region Y protein starts processes that cause a fetus to develop male gonads and prevents the formation of female gonads
![Page 20: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/20.jpg)
![Page 21: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/21.jpg)
![Page 22: Chapter 18: Regulation of Gene Expression - Sintich Sciencesintichscience.weebly.com/.../1_ch18_gene_expression.pdf · 2018-09-09 · Chapter 18: Regulation of Gene Expression . lism](https://reader033.vdocument.in/reader033/viewer/2022060501/5f1b8da4aad6a83b3c3b46f7/html5/thumbnails/22.jpg)
• Antifreeze gene – glycoprotein that prevents the formation or expansion of ice crystals in organism’s blood during periods of extreme cold
– The gene was discovered in 1969 in an Antarctic fish
– Organisms such as bacteria, fungi, plants, insects, and vertebrates
– Genetic engineering has been used to transfer the antifreeze gene from one organism to another to impart cold resistance