Gene Regulation How does a cell known what gene to express at a given time? 12-5

By the end of this lesson, you should be able to: 1) Describe a gene 2) Explain how prokaryotes control gene expression by looking at the lac gene 3) Explain how eukaryotes control gene expression 4) Relate gene expression to development

Entrance Question Compare the function of RNA & DNA Compare the function of RNA & DNA RNA Function DNA Function Synthesizes (makes) proteins Holds all of the cell ’ s instructions for making proteins

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 protein your body needs? Do they all know how to make every protein your body needs? Are they all making every possible protein that you need all of the time? Are they all making every possible protein that you need all of the time? How does each cell know what protein to make and when to make it? How does each cell know what protein to make and when to make it?

Gene Regulation Gene Expression – determines whether or not your cell is transcribbing a particular gene SWITCHED ON  Transcribbing the DNA and making the protein it codes for SWITCHED OFF  The gene is NOT transcribbed into RNA; it is “silent”

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

Lac gene Important Vocabulary : Operon – a group of genes that operate together Promoter – location on the DNA that is the binding site of the RNA polymerase

Lac Gene Important Vocabulary: Repressor – normally turns off the expression of the lac gene so RNA polymerase can ’ t bind to the DNA in the O region Lactose – a sugar that, if present binds to the repressor causing it to move from the gene so RNA polymerase 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: 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: Operons are not present Operons are not present Instead they have: Instead they have: TATA box – marks the beginning gene position for the RNA polymerase TATA box – marks the beginning gene position for the RNA polymerase Enhancer sequences – areas on the DNA before the gene that regulate gene expression when proteins bind to it Enhancer sequences – areas on the DNA before the gene that regulate gene expression when proteins bind to it

Another View…

Development and genes: As you grow from a zygote to your size today, your cells…… As you grow from a zygote to your size today, your cells…… 1) Divide 2) Differentiate – become specialized and take on different functions What controls differentation? What controls differentation? Your hox genes – special genes that control what parts of the body individual cells and tissues will develop into Your hox genes – special genes that control what parts of the body individual cells and tissues will develop into

Hox Genes What would happen if the hox genes were mutated?

Dr. Herrick’s Case Study: In 1904, a student from the West Indies came to the Chicago physician with a puzzling condition In 1904, a student from the West Indies came to the Chicago physician with a puzzling condition He feels well most of the time but reports odd recurring events like…. He feels well most of the time but reports odd recurring events like…. One day after a short swim he became tired and could hardly move One day after a short swim he became tired and could hardly move He was short of breath and had pain in his joints and muscles He was short of breath and had pain in his joints and muscles This lasted a few weeks and required some bed rest This lasted a few weeks and required some bed rest He also had frequent fevers and infections He also had frequent fevers and infections Dr. Herrick examined him and noticed the whites in his eyes had a yellowish tint Dr. Herrick examined him and noticed the whites in his eyes had a yellowish tint

Dr. Herrick’s Case Study Cont’d: His left abdominal area was tender to the touch and sore His left abdominal area was tender to the touch and sore His family history shows he has two brothers and three sisters, none with this condition His family history shows he has two brothers and three sisters, none with this condition However, his uncle and grandpa had similar conditions However, his uncle and grandpa had similar conditions His grandma died a young woman His grandma died a young woman His parents do not have this condition His parents do not have this condition Your Assignment: Do your medical research to find out the cause of this student ’ s situation. Describe what is happening to him and explain why. Your Assignment: Do your medical research to find out the cause of this student ’ s situation. Describe what is happening to him and explain why.