Transcript Genes
6D – Recognize that a gene expression is a regulated process. What is a gene? What do genes code for? protein What is gene expression? Process of using the genetic code in a gene to produce protein. It occurs in two steps: Transcription Translation DNA mRNA Protein Trait Simple Gene Expression https://highered.mheducation.com/sites/9 834092339/student_view0/chapter15/sim ple_gene_expression.html Learning Check If your birthday comes before your partner’s birthday, you are a partner A. Partner A – YOUR JOB: Explain in 15 sec the gene expression in your own words to your partner. Partner B – YOUR JOB: In 15 sec, repeat what the partner A said and add comments/corrections if needed. Different proteins are needed by different cells, which mean that different genes are expressed in different cells. All cells within an organism contain the same DNA sequence, but not all genes are used by all cells. • Some genes are always expressed. • Other genes are not expressed all the time and need to be turned on and off at need as a light switch – this needs to be regulated. Genes turned on determine cells’ function Learning Check Are all genes expressed (turned on) all the time? NO, only the genes that the cell need are transcribed into mRNA protein trait Why is the gene expression need to be regulated? Because some genes need to be turned ON and OFF at need. Why do different cells have different functions? Different genes are turned on in different cells different proteins are produced, which determine different functions. Gene expression is regulated by a cell. Gene regulation is the ability of an organism to control which genes are transcribed in response to environment. Learning Check 7 sec - Find a different partner In 10 sec, discuss the following with your partner: What is being controlled when the gene expression is regulated? Gene regulation in prokaryotes: An operon controls the transcription of several genes at the same time in response to changes in the environment. The lac operon consists of three genes (code for three enzymes) each involved in processing the sugar lactose. Lac = lactose The lac operon (Amoeba Sisters): https://www.youtube.com/watch?v=h_1QL dtF8d0 E.coli can use either glucose as a source of energy (monosaccharide) or lactose (disaccharide). Lactose needs to be hydrolyzed (digested) first, so bacterium prefers to use glucose. LACTOSE No lactose No enzymes needed to metabolize it = no waste repressor binds to the operator Blocks RNA polymerase NO transcription/translation NO protein (no enzymes) The lac operon is turned on only when glucose is absent, but lactose is present. Lactose present (enzymes are needed) Lactose binds to repressor and changes its shape= Can’t bind to the Operator RNA Polymerase transcribes genes into mRNA translation Enzymes are made to break down lactose sugar for energy Learning Check How do the prokaryotes such as E. coli adapt to the lack of food, glucose? Turn on the genes (the lac operon) that code for lactose synthesizing enzymes. Gene regulation in eukaryotes (more complex) Regulation occurs in all four stages: Gene 1 2 3 4 What can affect this expression? MUTATIONS Many factors can affect the rate of transcription and translation in living cells including: Changing in temperature or light; animals can change color or grow thicker fur coats in the winter. The presence or absence of nutrients in the environment; lactose present triggers E. coli to produce specific lactose synthesizing enzymes.