Question 1

What is gene regulation?

Accepted Answer

A mechanism for controlling which genes get expressed in cells, and at what levels

(in prokaryotes this can save huge amounts of energy by only creating the proteins required at the moment; in eukaryotes this allows for cell differentiation)

Question 2

What is a promoter?

Accepted Answer

A sequence of DNA that controls an operon, turning the operon's genes on/off

(usually found near the beginning of a gene; proteins bind to the promoter to initiate the transcription of RNA, which may encode for a protein)

Question 3

What are operons?

Accepted Answer

A cluster of genes under the control of a single promoter

(common in prokaryotes (bacteria), but very rare in eukaryotes (humans); all the genes function in the same process)

Question 4

What are regulatory DNA sequences?

Accepted Answer

DNA sequences that control the transcription of the operon

(also serve as binding sites for regulatory proteins, which control how much the operon is transcribed)

Question 5

What are repressors?

Accepted Answer

A type of regulatory protein that binds to operators, reducing transcription

(might block the RNA polymerase from moving forwards on the DNA)

Question 6

What are activators?

Accepted Answer

A type of regulatory protein that binds to the DNA binding site, increasing transcription of the operator

(might help the RNA polymerase bind to the promoter)

Question 7

What are operators?

Accepted Answer

A sequence of DNA that allows proteins responsible for transcription (into some type of RNA) to attach to a DNA sequence

(structural genes (code for synthesis of specific polypeptides) are connected with operators inside of the operon, and the operon as a whole can be turned on/off by the promoter)

Question 8

What are regulatory genes?

Accepted Answer

Genes that encode regulatory proteins

(e.g., a gene that codes for repressor proteins that inhibit transcription)

Question 9

What are regulatory proteins?

Accepted Answer

Proteins that control how much the operator is transcribed

Question 10

What are inducible and repressible operons?

Accepted Answer

Inducible operons are "off" by default, but can be turned "on" by a small molecule called an inducer (e.g., lac operon)

Repressible operons are "on" by default, but can be turned "off" by a small molecule called a corepressor (e.g., trp operon)

Question 11

What are housekeeping genes?

Accepted Answer

Genes that are constantly expressed because their products are needed by the cell to maintain essential functions

(opposite of genes that are regulated to only be expressed sometimes; housekeeping genes still have their own promoters and regulation to keep them active)

Question 12

What is the lac operon?

Accepted Answer

A famous inducible operon that is essential for transporting and metabolizing lactose in E.coli

(only turned on when the E.coli has lactose available but doesn't have glucose (it's preferred food))

Question 13

What is the trp operon?

Accepted Answer

A famous repressible operon that is responsible for making tryptophan (type of amino acid) in E.coli

(the trp repressor detects when there is already a lot of tryptophan in the cell, and tells the trp operon to stop making more)

Question 14

What is the purpose of gene regulation in eukaryotes?

Accepted Answer

Controls which cells of an organism are expressed so that different cells can perform different functions

Question 15

How do cells "decide" which genes to turn on?

Accepted Answer

Two main ways (although there are many others):

Internal Information: proteins it inherited from its mother cell, whether its DNA is damaged, and how much ATP it has

External Information: chemical signals from other cells, mechanical signals, and nutrient levels

Question 16

What are transcription factors?

Accepted Answer

Helper proteins that control the rate of genetic transcription

Turns genes "on/off" by binding to nearby DNA

Gene Regulation, AP Biology Flashcards