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AP Biology 2014 > Operons > Flashcards

Flashcards in Operons Deck (11):

What is an operon?

A unit of DNA by which the expression of specific genes is controlled

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What are operons composed of? 

PROG: Promoter, Repressor, Operator, Genes 


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What is a promoter?

The region at which RNA polymerase binds to a DNA strand.

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What is a repressor and how does it work?

A repressor is a specific protein that binds to the operator, blocking the attachment of RNA polymerase, and preventing the transciption of genes. It originates from a regulatory gene separate from the operon at which the repressor functions. With the help of small molecules known as corepressors, which activate the repressor, or inducers, which deactivate them, repressors work to appropriately block the production of certain enzymes. 

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What is an operator?

A region of DNA which controls the access of RNA polymerase to the genes. Acts as an on or off switch depending on the presence of a repressor. 

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What do the genes do?

With the help of RNA polymerase, the genes at the end of the operon transcribe and translate into proteins that make up specialized enzymes. These enzymes complete specific tasks such as breaking down lactose or creating tryptophan 

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What are the two types of operons?

Inducible and Repressible Operons


How do inducible operons work>

Inducible operons are usually off, because of the presence of an active repressor, but can be induced, or stimulated, in the presence of a small molecule (inducer) 


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Through what type of pathways do inducible enzymes work?

Inducible enzymes usually function in catabolic pathways: "a sequence of degradative chemical reactions that break down complex molecules into smaller units, usually releasing energy in the process" (biology-online.org)



How do repressible operons work?

Repressible operons are usually on, because of the presence of an inactive repressor, but can be activated with the presence of a small molecule (corepressor) 


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Through what type of pathways do repressible enzymes work?

Repressible enzymes usually function in anabolic pathways: "the series of chemical reactions that constructs or synthesizes molecules from smaller units, usually requiring input of energy (ATP) in the process" (biology-online.org).