CONSTITUTIVE GENE PRODUCTS ARE NEEDED BY THE BODY AT ALL TIMES TUMOR SUPRESSOR PROTEINS ATP ENZYMES THAT CONTROL CELLULAR RESPIRATION ADAPTIVE GENE PRODUCTS ARE ONLY REQUIRED UNDER CERTAIN CONDITIONS ID: 425133
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Slide1
GENE EXPRESSIONSlide2
CONSTITUTIVE GENE PRODUCTS ARE NEEDED BY THE BODY AT ALL TIMES
TUMOR SUPRESSOR PROTEINS
ATP
ENZYMES THAT CONTROL CELLULAR RESPIRATIONSlide3
ADAPTIVE GENE PRODUCTS ARE ONLY REQUIRED UNDER CERTAIN CONDITIONSGENES FOR PROTEIN DIGESTION ARE TURNED OFF WHEN THERE IS NO PROTEIN AVAILABLE. Slide4
THE LAC OPERON
Transcription in bacteria is an easy process. Transcription is initiated when RNA polymerase binds to the promoter. This occurs when there is an inducer present in the bacteria (
activation
). If there is no inducer, the process is physically unable to occur (
repression
).
EX: Bacteria use the sugar lactose for energy. They break down lactose with the aide of the enzyme lactase. Lactase will only be made if necessary. This will save the bacteria energy. If lactose, the inducer, is not present, than transcription of the mRNA that is translated into lactase is not made.Once enough mRNA is produced, it is immediately translated, even if the entire mRNA strand is not completed. Slide5
3 parts to an operonPromoter – site where RNA polymerase binds to start transcriptionOperator – on/off switchStructural gene(s) – codes for the protein
Repression – no inducer is present. Bacteria have regulatory genes that control their expression. This gene produces the repressor protein.
If there is no inducer, the repressor protein latches onto the operator and turns the operon “off” by physically blocking RNA polymerase from performing transcription.
No mRNA is made. Therefore, no protein.
Activation – inducer is present
The repressor protein is latched on to the operator. The inducer comes and attaches to the repressor protein, causing it to change it shape and let go of the operator.
The operon is now “on” and RNA polymerase can move through and transcribe the gene.mRNA is made. The protein is made.Activation will lead to repression once all of the inducer is broken down by the protein, as there will be none left to grab onto the repressor protein.Slide6Slide7
EUKARYOTIC GENE EXPRESSION
ONLY EUCHROMATIN CAN BE TRANSCRIBED
TRANSCRIPTION IS SPATIALLY AND TEMPORALLY SEPARATED FROM TRANSLATION
DNA IS MORE COMPLEX BECAUSE A GREATER NUMBER OF GENE PRODUCTS ARE NEEDED FOR SPECIALIZED FUNCTIONS.Slide8Slide9Slide10
EUKARYOTIC PROMOTERS (1)
Promoters are the binding site of RNA polymeraseTATA box: an 8-base pair repeating sequence of TATATATA in the promoter that helps RNA polymerase bind
CCAAT box: another sequence in the promoter DNA that helps RNA polymerase bind.
Both are located in front of the genes that will be transcribed.Slide11
ENHANCERS: Non-coding control sequences in Eukaryotic DNA located in front of the promoter. Enhancers must be activated for a gene to be expressed.
.Slide12
THE STEROID TESTOSTERONE IS ALSO A TRANSCRIPTION FACTOR. MANY STEROIDS AND HORMONES ARE TRANSCRIPTION FACTORS AND HELP TO REGULATE GENE EXPRESSION.
Transcription Factors:
.Transcription factors are substances that activate enhancers and cause protein productionSlide13
ANABOLIC STEROIDS:known commonly for their illegal use by athletes, anabolic steroids are used medically to treat growth abnormalities, anemia, leukemia, kidney failure, and other medical problems.Slide14Slide15
Transcription produces a molecule called pre-mRNA, which is made in the nucleus. Then it is edited and spliced together to form mRNA. The mRNA goes to the cytoplasm. (2)Slide16
Pre-mRNA is very similar for all vertebrates. Splicing is done per organism to make us unique. Slide17Slide18
From a gene on a chromosome to a sequence of amino acids to a protein.Slide19
THINK ABOUT IT . . .
Our structural genes contain information to make products from all organisms, amoeba to zebra. We
transcribe
it all. We
translate
only selected
exons. Slide20
IN MOST MAMMAL CELLS, ONLY 1% OF DNA IS COPIED INTO FUNCTIONAL RNA
Over our existence on the planet, “junk” DNA has been added to our DNA. Junk DNA is DNA that seems to have no purpose. One theory is that junk DNA is made of viral sequences inserted into our genome. Slide21
Control of gene expression (3, 4, &5):