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: • Describe a gene • Explain how prokaryotes control gene expression by looking at the lac gene • Explain how eukaryotes control gene expression • Relate gene expression to development
Entrance Question • Compare the function of RNA & DNA
Now, think about this…. • Do all of your cells hold the same DNA? • Do they all have the same instructions? • 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? • 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. colistrains are harmless, but some can cause serious food poisoning in humans, and are occasionally responsible for costly product recalls. The harmlessstrains 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.
Lac geneImportant Vocabulary : Operon – a group of genes that operate together Promoter – location on the DNA that is the binding site of the RNA polymerase
Lac GeneImportant 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!!!! • What were introns and exons? • What else looks different?
Differences: • Operons are not present • Instead they have: • 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
Development and genes: • As you grow from a zygote to your size today, your cells…… • Divide • Differentiate – become specialized and take on different functions • What controls differentation? • 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 • 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 • He was short of breath and had pain in his joints and muscles • This lasted a few weeks and required some bed rest • He also had frequent fevers and infections • 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 family history shows he has two brothers and three sisters, none with this condition • However, his uncle and grandpa had similar conditions • His grandma died a young woman • 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.