Free · AP Biology · revision map

6.5 Regulation of Gene Expression: revision map

The subtopic in the middle and four tasks round it: label a diagram, complete a table, put a process in order and fill 9 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

Unit 6 practice questions The whole Unit 6 map

Topic 6.5

Regulation of Gene Expression

AP Biology · Unit 6 Gene Expression and RegulationName

6.5.A, 6.5.BThe lac operon with no lactose

123456

6.5.ASwitching the operon on

Number the steps in order.

The structural genes are transcribed.
RNA polymerase can now bind to the promoter.
Lactose is present, and a form of it binds to the repressor.
The repressor changes shape and falls off the operator.
The enzymes that digest lactose are made.

Topic 6.5Regulation of Gene Expression

6.5.ATwo kinds of operon

	Inducible (lac)	Repressible (trp)
Normal state	off
Switched by	the substrate, lactose, which inactivates the repressor	the end product, tryptophan, which the repressor
Effect	enzymes made only when lactose is there	enzymes made only when tryptophan is short
Control type	negative	negative

6.5.BControl in eukaryotes

Eukaryotes control genes at many steps, and mostly at transcription. Proteins called bind to DNA sequences near a gene, or to enhancers far away, and help or block RNA polymerase. DNA wrapped tightly round histones is not transcribed: adding methyl groups to DNA, or removing acetyl groups from histones, tightens the packing, and the opposite changes loosen it. These marks are epigenetic: they alter gene expression without changing the DNA sequence, and some are passed on when cells divide.

Word bank activatesonoperatorpromoterregulatory generepressorRNA polymerasestructural genestranscription factors

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

LabelThe lac operon with no lactose
1. regulatory gene
2. promoter
3. operator
4. repressor
5. structural genes
6. RNA polymerase
OrderSwitching the operon on
1. Lactose is present, and a form of it binds to the repressor.
2. The repressor changes shape and falls off the operator.
3. RNA polymerase can now bind to the promoter.
4. The structural genes are transcribed.
5. The enzymes that digest lactose are made.

TableTwo kinds of operon

	Inducible (lac)	Repressible (trp)
Normal state	off	on
Switched by	the substrate, lactose, which inactivates the repressor	the end product, tryptophan, which activates the repressor
Effect	enzymes made only when lactose is there	enzymes made only when tryptophan is short
Control type	negative	negative

GapsControl in eukaryotes
Eukaryotes control genes at many steps, and mostly at transcription. Proteins called transcription factors bind to DNA sequences near a gene, or to enhancers far away, and help or block RNA polymerase. DNA wrapped tightly round histones is not transcribed: adding methyl groups to DNA, or removing acetyl groups from histones, tightens the packing, and the opposite changes loosen it. These marks are epigenetic: they alter gene expression without changing the DNA sequence, and some are passed on when cells divide.