bacterial genetics and operons, student learning guide

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sciencemusicvideos Bacterial Genetics and Operons, Student Learning Guide Getting to the tutorials • Go to www.sciencemusicvideos.com; Use the College Bio, AP Bio, or Learning Guide Menus to find “Bacterial Genetic

Diversity and Bacterial Gene Regulation (Operons).”” • Start with “Sources of Genetic Diversity in Bacteria.”

Tutorial 1. Sources of Genetic Diversity in Bacteria 1. Read “1. Shouldn’t all the bacteria of the same species be clones?” Check this box when you’re finished. ☐ CHECKING UNDERSTANDING: Why, based on how bacteria reproduce, would you expect all bacteria of the same species be clones?” Make a key to the diagram below. Identify each labeled part, and write a short description of each numbered step.

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2a. Read about Mutation. ☐ 2b. Read about transformation, starting with the one question quiz showing Frederick Griffith’s demonstration of the transforming factor in pneumonia causing bacteria. Write your own explanation in the space below, then adjust your answer as needed after clicking “Show me the answer.” You can continue your answer on the top of the next column.

Explain briefly how the two forms of transformation are different. Make a key to the diagrams below. Same instructions as for the previous diagram.

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2c. Read about bacterial conjugation. ☐ Make a key to the diagram below. Note that there’s no letter “d”

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2d. Transduction


We learned about transduction in the previous unit. See if you make a key for the diagram below. If you’re having difficulty, go back and review the material in module 15 and complete the key.

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2e. Read the section about transposition, and study the associated diagrams. ☐ REFLECT: How are transposons similar to viruses? How are they different? Make a key for the diagram below.

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Now make a key for this one:

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3. Take the “Bacterial Genetic Diversity: Checking Understanding” Quiz ☐ SYNTHESIZING WHAT YOU’VE LEARNED A student taking 9th grade biology says to you “aren’t all bacteria clones?” Tell them what you know about the sources of diversity in bacteria. Write small. Click the link to “Operons,” the next tutorial


Tutorial 2: Operons 1. If it’s useful, click through the slides. 2. Read the introduction, and, in the space below, use what you know about natural selection to explain why control of gene expression is of great survival value. 3. Read “Operons: Description and Definition.” ☐ 4. Read “The Lac Operon” ☐ 5. Complete the “Lac Operon: Labeled Diagrams” ☐

Explain it. The diagram below shows the lac operon when lactose is absent.

This diagram shows the operon when lactose is present

In the space below, write a paragraph that explains how the lac operon works. As you do, make sure that you explain each numbered part in the diagram.

6. Read “The Tryp Operon” ☐ 7. Complete the “Tryp Operon: Labeled Diagrams” ☐ 8. Take the Operons Quiz ☐ Explain it The diagram below shows the tryp operon in the presence of tryptophan

And this shows the tryp operon in the absence of tryptophan.

In the space below, write a paragraph explaining how the tryp operon works. Again, make sure you explain each numbered part of the diagram.


9. Read about CAP, stopping at the horizontal line. ☐ SPECULATE: What’s happening in the single food (glucose only) E. coli growth curve below? Why is there a lag in growth when E. coli is fed two foods (such as glucose and lactose?)

Fill the space below with your speculations. Read the rest of the passage explaining how CAP works. ☐

YOU EXPLAIN IT Here’s the CAP system when glucose and lactose are present:

And here’s the system when glucose is scarce and lactose levels are high.

Explain how this system enable an E. coli cell to “choose” glucose over lactose when both are available, and then to turn to lactose only when glucose supplies are scarce.


sciencemusicvideos | Biology Name:________________________

Bacterial Genetics and Operons

Across: Down: 2 - Picking up DNA in the environment 5 - A disaccharide that is found in milk. 7 - This type of AMP is produced by the cell when glucose is in short supply. 9 - "In an operon, these are the genes that code for enzymes." 11 - A DNA element that can move from one position in the genome to another 12 - A DNA region just "downstream" of the promoter, where regulatory proteins can bind. 14 - Both the trp and lac operons involve __________ regulation (through repressors). 15 - Operons only work because regulatory proteins are subject to ___________ regulation. 17 - random change in DNA 18 - The area where RNA polymerase binds. 19 - The amino acid that is the regulated product of the trp operon. 20 - These genes produces regulatory proteins, which control transcription 21 - E. coli reproduces though binary ________ 22 - An extra-chromosomal circle of DNA

1 - The lac operon is an _______________ system (think about what lactose does) 3 - The enzyme reverse ___________ is required in the retrotransposon life cycle. 4 - A DNA element that must make itself into RNA before sending a DNA copy of itself to another location in the genome 6 - Operons are mostly about control of _____________ of related genes. 8 - E. coli's home 10 - The trp operon is a ______________ system (think about what tryptophan does) 11 - Gene transfer that occurs when viruses carry bacterial DNA from one cell to another 13 - When one bacterial cell passes a copy of its plasmid to another. 16 - A cluster of genes under the control of a single promoter. 18 - A cellular extension used during conjugation.

Possible Answers: Lactose, allosteric, colon, conjugation, cyclic, fission, inducible, mutation, negative, operator, operon, pilus, plasmid, promoter, regulatory, repressible, retrotransposon, structural, transcriptase, transcription, transduction, transformation, transposon, tryptophan

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bacterial genetics and operons, student learning guide

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