Gene RegulationGene Regulation

How does a cell known what How does a cell known what gene to express at a given gene to express at a given

time?time?

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By the end of this lesson, you By the end of this lesson, you should be able to:should be able to:

1)1) Describe a geneDescribe a gene

2)2) Explain how prokaryotes control Explain how prokaryotes control gene expression by looking at the gene expression by looking at the laclac gene gene

3)3) Explain how eukaryotes control Explain how eukaryotes control gene expression gene expression

4)4) Relate gene expression to Relate gene expression to developmentdevelopment

Entrance QuestionEntrance Question Compare the function of RNA & DNACompare the function of RNA & DNA

RNA FunctionRNA Function DNA FunctionDNA Function

Synthesizes (makes) Synthesizes (makes) proteinsproteins

Holds all of the cellHolds all of the cell’’s s instructions for instructions for making proteinsmaking proteins

Now, think about this….Now, think about this….

Do all of your cells hold the same DNA?Do all of your cells hold the same DNA? Do they all have the same instructions?Do they all have the same instructions? Do they all know how to make every Do they all know how to make every

protein your body needs?protein your body needs? Are they all making every possible Are they all making every possible

protein that you need all of the time?protein that you need all of the time? How does each cell know what protein How does each cell know what protein

to make and when to make it?to make and when to make it?

Gene RegulationGene Regulation

Gene Expression – determines whether Gene Expression – determines whether or not your cell is transcribbing a or not your cell is transcribbing a particular geneparticular gene

SWITCHED ONSWITCHED ON Transcribbing the Transcribbing the DNA and making the protein it codes forDNA and making the protein it codes for

SWITCHED OFFSWITCHED OFF The gene is NOT The gene is NOT transcribbed into RNA; it is “silent”transcribbed into RNA; it is “silent”

Prokaryotic Gene RegulationProkaryotic Gene RegulationEscherichia coliEscherichia coli - - ((E. coliE. coli), is a ), is a bacterium

that is commonly found in the lower that is commonly found in the lower intestine of warm-blooded animals. Most of warm-blooded animals. Most E. coliE. coli strains are harmless, but some can are harmless, but some can cause serious food poisoning in humans, cause serious food poisoning in humans, and are occasionally responsible for and are occasionally responsible for costly product recalls. The harmless costly product recalls. The harmless strains are part of the normal flora of the strains are part of the normal flora of the gut, and can benefit their hosts by gut, and can benefit their hosts by producing vitamin K2, or by preventing producing vitamin K2, or by preventing the establishment of pathogenic bacteria the establishment of pathogenic bacteria within the intestine. within the intestine.

Lac geneLac geneImportant Vocabulary :Important Vocabulary :

OperonOperon – a group of genes that operate – a group of genes that operate togethertogether

PromoterPromoter – location on the DNA that is the – location on the DNA that is the binding site of the RNA polymerasebinding site of the RNA polymerase

Lac GeneLac GeneImportant Vocabulary:Important Vocabulary:

RepressorRepressor – normally turns off the expression of the – normally turns off the expression of the lac gene so RNA polymerase canlac gene so RNA polymerase can’’t bind to the DNA t bind to the DNA in the O regionin the O region

Lactose Lactose – a sugar that, if present binds to the – a sugar that, if present binds to the repressor causing it to move from the gene so RNA repressor causing it to move from the gene so RNA polymerase can bind and the lac gene is expressedpolymerase can bind and the lac gene is expressed

O region = Operator – the region on the DNA that controls gene expresssion by turning “on” or “off”

Eukaryotic Gene Regulation:Eukaryotic Gene Regulation:

MUCH MORE COMPLEX!!!!MUCH MORE COMPLEX!!!! What were introns and exons?What were introns and exons? What else looks different?What else looks different?

Differences:Differences:

Operons are not presentOperons are not present Instead they have:Instead they have:

TATA box – marks the beginning gene TATA box – marks the beginning gene position for the RNA polymeraseposition for the RNA polymerase

Enhancer sequences – areas on the DNA Enhancer sequences – areas on the DNA before the gene that regulate gene before the gene that regulate gene expression when proteins bind to itexpression when proteins bind to it

Another View…Another View…

Development and genes:Development and genes: As you grow from a zygote to your As you grow from a zygote to your

size today, your cells……size today, your cells……1)1) DivideDivide2)2) Differentiate – become specialized Differentiate – become specialized

and take on different functionsand take on different functions What controls differentation?What controls differentation?

Your hox genes – special genes that Your hox genes – special genes that control what parts of the body control what parts of the body individual cells and tissues will develop individual cells and tissues will develop intointo

Hox GenesHox Genes

What would happen if the hox genes were mutated?

Dr. HerrickDr. Herrick’’s Case Study:s Case Study: In 1904, a student from the West Indies came In 1904, a student from the West Indies came

to the Chicago physician with a puzzling to the Chicago physician with a puzzling conditioncondition

He feels well most of the time but reports odd He feels well most of the time but reports odd recurring events like….recurring events like….

One day after a short swim he became tired One day after a short swim he became tired and could hardly moveand could hardly move

He was short of breath and had pain in his He was short of breath and had pain in his joints and musclesjoints and muscles

This lasted a few weeks and required some bed This lasted a few weeks and required some bed restrest

He also had frequent fevers and infectionsHe also had frequent fevers and infections Dr. Herrick examined him and noticed the Dr. Herrick examined him and noticed the

whites in his eyes had a yellowish tintwhites in his eyes had a yellowish tint

Dr. HerrickDr. Herrick’’s Case Study s Case Study ContCont’’d:d:

His left abdominal area was tender to the His left abdominal area was tender to the touch and soretouch and sore

His family history shows he has two brothers His family history shows he has two brothers and three sisters, none with this conditionand three sisters, none with this condition

However, his uncle and grandpa had similar However, his uncle and grandpa had similar conditionsconditions

His grandma died a young womanHis grandma died a young woman His parents do not have this conditionHis parents do not have this condition Your Assignment:Your Assignment: Do your medical Do your medical

research to find out the cause of this studenresearch to find out the cause of this studentt ’’s situation. Describe what is happening to s situation. Describe what is happening to him and explain why.him and explain why.