Biology 1 Chapter 16- Gene Expression

By emilyannedollar | Updated: Dec. 6, 2018, 7:21 p.m.

Slideshow Video

SHARE THE AWESOMENESS

Education

create your own animated videos for free

_abc cc

* Powtoon is not liable for any 3rd party content used. It is the responsibility of each user to comply with 3rd party copyright laws.

Embed code

Select a size, the embed code changes based on your selection.

_abc Powtoon Transcript

Gene expression
Chapter 16
By Emily Dollar
Prokaryotic vs. Eurkaryotic Gene Expression
Chapter 16
Prokaryotic Cells
Single celled organisms that lack a nucleus
DNA floats freely in the cell cytoplasm
Synthesize protein by process of transcription and translation almost simultaneously 
Regulation of DNA transcription helps determine how much of each protein is expressed 
Gene control at transcriptional level 
DNA is organized into a circular chromosome that is supercoiled in the nucleoid region of the cell cytoplasm 
(OpenStax College, 2018)
Gene Expression components 
in prokaryotic cells
Operons
Repressors
Activators
Inducers
Prokaryotic cell image (Khan Academy, 2016).
Operons- Proteins that are needed for a specific function or that are involved in the same biochemical pathway and are encoded together in blocks
Repressors- proteins that suppress transcription of a gene in response to an external stimulus 
Activators- proteins that increase the transcription of a gene in response to an external stimulus
Inducers- small molecules that either activate or repress transcription depending on the needs of the cell and the availability of the substrate.
(OpenStax, 2018).
&
(Lumen, 2007)
How operons, repressors, activators, and inducers work together
"There are two different types of gene regulation: positive and negative. Activators (and sometimes inducers) instigate positive regulation, and repressors instigate negative regulation. When an activator or inducer binds to an operon, the transcription process either increases in rate or is allowed to continue. When a repressor binds to an operon, the transcription process is slowed or halted" (Lumen, 2007).
(Khan Academy, 2016)
Activators vs. Repressors
"The protein CAP is an activator. When cAMP is present, CAP binds to the promoter and increases RNA polymerase activity. Without cAMP, CAP does not bind to the promoter. Transcription will occur at a lower rate."
"When an amino acid is present and associates with the met repressor, the repressor is activated. RNA synthesis is stopped by the presence of the repressor on the DNA strand. When the amino acid is not there, the repressor moves away from the operator and RNA synthesis continues."
(Lumen, 2007)
Tryptophan (trp) operon
"The trp operon of E. coli controls the biosynthesis of tryptophan in the cell from the initial precursor chorismic acid. This operon contains genes for the production of five proteins which are used to produce three enzymes. The products of the E and D genes form a multimeric protein comprised of two copies of each protein to produce the enzyme anthranilate synthetase. This enzyme catalyzes the first two reactions in the tryptophan pathway. The next enzyme, which is responsible for catalyzing the next two steps in the pathway is indole glycerolphosphate synthetase and it is the product of the C locus. The final step in the reaction is the pathway produces tryptophan from indole-glycerol phosphate and serine. This single step is catalyzed by tryptophan synthetase, an enzyme that is a multimer of two proteins that are the product of the B and A genes." (Phillip McClean, 1997)
lac Operon
-encodes the genes necessary to acquire and process the lactose from the local environment (William & Flora Hewlett Foundation, Bill & Melinda Gates Foundation, Michelson 20MM Foundation, Maxfield Foundation, Open Society Foundations, and Rice University., 2018)
It is found in E coli. 
Has genes that are involved in lactose metabolism
It is expressed when only lactose is present and not glucose.
Has 2 parts:
1.) lac repressor- gages levels of lactose, blocks transcription of operon unless lactose is present. It senses lactose through its isomer allolactose.
2.) Catabolite activator protein (CAP)- gages levels of glucose, activates transcription of operon when glucose levels are low. It senses glucose through the molecule cAMP.
(Khan Academy, 2016)
Overall picture of Prokaryotic Gene Expression
(Nature Education, 2014)
Also...in case you forgot
Transcription
" is the process of making an RNA copy of a gene sequence. This copy, called a messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where it directs the synthesis of the protein, which it encodes."
Translation
"is the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis. The genetic code describes the relationship between the sequence of base pairs in a gene and the corresponding amino acid sequence that it encodes. In the cell cytoplasm, the ribosome reads the sequence of the mRNA in groups of three bases to assemble the protein."
(National Human Genome Institute , 2003)
Gene Expression
in eukaryotic cells
Animal Cell
AND 
Plant Cell
Eurkaryotic cell image (Khan Academy, 2016)
Eurkaryotic Cells
Have intracellular organelles
DNA is contained inside the cell’s nucleus and there it is transcribed into RNA
newly synthesized RNA is then transported out of the nucleus into the cytoplasm, where ribosomes translate the RNA into protein
transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm.
(OpenStax College, 2018)
Have multiple linera chromosomes
cis-acting element- area where transcription factors bind to promoter that is just upstream of of the encoded gene
Transcription factor binding site- region where particular transcription factor binds to
Enhancers- regions that help increase or enhance transcription
Transcriptional repressors- bind to promoter or enhancer regions and block transcription
(OpenStax College, 2018)
How Eurkaryotic Cells control RNA Stability
5' cap- at the beginning of an RNA transcript 
3' poly-A tail- at the end of the RNA transcript 
First, pre-mRNA has to be processed into messenger RNA (mRNA).
Splicing
Introns- removed section of RNA transcript 
Exons- remaining RNA transcripts that are put back together 
(Khan Academy, 2016).
Alternative RNA Splicing 
"Process in which more than one mRNA can be made from the same gene (Khan Academy, 2016)". 
Untranslated Regions (UTRs)
RNA regions that are not translated into proteins
5' UTR is before the protein coding region and 3' UTR is after the coding region
(OpenStax College, 2018)
microRNAs
short segments of RNA molecules that are made into longer pre-miRNAs in the nucleus. They are 21-24 nucleotides in length
a DICER protein then comes along and splits pre-miRNAs into mature miRNAs
RISC (RNA-induced silencing complex) then binds with miRNA to destroy the RNA molecule 
(OpenStax College, 2018).
Initiation Complex
Start process of of translation in Eurkaryotes
"The first protein to bind to the RNA to initiate translation is the eukaryotic initiation factor-2 (eIF-2). The eIF-2 protein is active when it binds to the high-energy molecule guanosine triphosphate (GTP). GTP provides the energy to start the reaction by giving up a phosphate and becoming guanosine diphosphate (GDP). The eIF-2 protein bound to GTP binds to the small 40S ribosomal subunit. When bound, the methionine initiator tRNA associates with the eIF-2/40S ribosome complex, bringing along with it the mRNA to be translated. At this point, when the initiator complex is assembled, the GTP is converted into GDP and energy is released. The phosphate and the eIF-2 protein are released from the complex and the large 60S ribosomal subunit binds to translate the RNA. The binding of eIF-2 to the RNA is controlled by phosphorylation. If eIF-2 is phosphorylated, it undergoes a conformational change and cannot bind to GTP. Therefore, the initiation complex cannot form properly and translation is impeded (Figure). When eIF-2 remains unphosphorylated, it binds the RNA and actively translates the protein (OpenStax College, 2018)". 
To better understand the Initiation Complex...
And watch this helpful video!!!
https://youtu.be/qIwrhUrvX-k
(OpenStax College, 2018).
Chemical Modifications in Gene Expression
These responses occur due to external stimuli such as stress, lack of nutrients, heat, and light exposure.
This can occur to proteins with the addition or removal of groups like methyl, phosphate, acetyl, and ubiquitin groups. 
Changes in the external stimuli can alter epigenetic accessibility, transcription, mRNA stability, or translation.
This in turn, is how a cell changes levels of proteins to suit its environment.

(Nature Education, 2014).
Cancer
"...a disease of altered gene expression (OpenStax College, 2018)".
"...a disease of uncontrolled cell division (Khan Academy, 2016)". 
In this case, gene regulation and mutation can cause can cause silent genes to be turned on and form into cancer (OpenStax College, 2018).
Histone acetylation
When it is changed and no longer regulates gene silencing, cancer can then be detected
Tumor Suppressor Genes
Act to prevent abnormal cell growth in normal cells
Myc
Type of transcription factor activated in lymph system cancer. It also causes normal B cells to change and grow out of control.
OpenStax College, 2018).
Epigenetic Alterations in Cancer
"biological mechanisms that will switch genes on and off."
"everything around is related to epigenetics, and it can cause chemical modifications that turn genes on or off". 
"The effects of the gene that an be turned on and off are reversible."
(Khan Academy, 2016).
(Educationally Entertaining, 2018)
Transcriptional Control
"Mutations that activate transcription factors, such as increased phosphorylation, can increase the binding of a transcription factor to its binding site in a promoter. This could lead to increased transcriptional activation of that gene that results in modified cell growth."
Post-transcriptional Control
"Some cancers alter expressions of miRNAs. Because miRNAs bind to the 3' UTR of RNA molecules to degrade them, overexpression of these miRNAs could be detrimental to normal cellular activity. Too many miRNAs could dramatically decrease the RNA population leading to a decrease in protein expression."
Translational/Post-translational Control
"Modifications are found in cancer cells from the increased translation of a protein to changes in protein phosphorylation to alternative splice variants of a protein. Clearly, the expression of the wrong protein dramatically alters cell function and contributes to the development of cancer.
(OpenStax College, 2018)
Drugs to fight off Cancer 
"Scientists are using what is known about the regulation of gene expression in disease states, including cancer, to develop new ways to treat and prevent disease development."
"One such example is the use of anti-EGF receptor medications to treat the subset of breast cancer tumors that have very high levels of the EGF protein."
(OpenStax, 2018).
Works Cited
“A Super Brief and Basic Explanation of Epigenetics for Total Beginners.” What Is Epigenetics?, WhatIsEpigenetics.com, 18 Oct. 2018, www.whatisepigenetics.com/what-is-epigenetics/.
Learning, L. (n.d.). Biology for Majors I. Retrieved from https://courses.lumenlearning.com/wmopen-biology1/activators-and-repressors/
(n.d.). Retrieved from https://cnx.org/contents/GFy_h8cu@11.1:mg3jT_xX@3/Introduction
(n.d.). Retrieved from https://www.ndsu.edu/pubweb/~mcclean/plsc431/prokaryo/prokaryo3.htm
(n.d.). Retrieved from https://www.nature.com/scitable/topicpage/operons-and-prokaryotic-gene-regulation-992
The lac operon. (n.d.). Retrieved from https://www.khanacademy.org/science/biology/gene-regulation/gene-regulation-in-bacteria/a/the-lac-operon
Transcription and Translation. (n.d.). Retrieved November 21, 2018, from https://www.genome.gov/27552603/transcription-and-translation/

Biology 1 Chapter 16- Gene Expression

Copy this link to share with friends and colleagues:

WELCOME TO POWTOON!