When DNA is compacted by histones into 10 nm and 30 nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

• methylation and phosphorylation of histone tails

• nucleotide excision and reconstruction

What does the operon model attempt to explain?

• the coordinated control of gene expression in bacteria

• the mechanism of viral attachment to a host cell

The tryptophan operon is a repressible operon that is

• turned off whenever tryptophan is added to the growth medium

• turned on only when glucose is present in the growth medium.

Tags

NGSS.HS-LS1-3

Altering patterns of gene expression in prokaryotes would most likely serve the organismʹs survival in which of the following ways?

• allowing the organism to adjust to changes in environmental conditions

• organizing gene expression so that genes are expressed in a given order

• allowing environmental changes to alter the prokaryoteʹs genome

When present in the cell, IPTG binds to ​ (a)   which can then no longer bind to the ​ (b)   . Thus, ​ (c)   will be able to be expressed.​

• T7 expression host

• inducible promoter

• lac repressor

• lac promoter

• T7 polymerase

• plasmid

• GFP

The initial steps in gene expression are modeled. Double-stranded DNA first unwinds into two strands. Which process and product are represented in the diagrams?

• Process: transcription; product: mRNA

• Process: translation; product: protein

• Process: replication; product: tRNA

• Process: recombination; product: polymerase

Tags

NGSS.HS-LS1-1

This can inhibit transcription by blocking the binding of positively acting transcription factors to the DNA:

• enhancer

• promoter

• repressor

Where does RNA polymerase bind to DNA?

• at an activator site

• on the coding gene sequence

• at a promoter region

• downstream of the coding sequence

• Where the RNA primer is placed

Bacterial cells that contain pGal will fluoresce blue under ultraviolet light. Which of the following is the most likely outcome of replacing the lacA gene in the E. coli lac operon with the gene encoding pGal?

• When lacY and lac Z are breaking down and transporting lactose, the bacteria will fluoresce blue under ultraviolet light

• lacZ will only produce the enzyme for breaking down galactose in the presence of ultraviolet light

• the repressor enzyme will only be able to bind to the operator under the presence of lactose

• When the regulatory gene is stimulated by lactose, it will cause the gene to fluoresce blue

• All structural genes downstream from the placement of lacA will be inhibited due to this substitution mutation.

Tags

NGSS.HS-LS1-1

NGSS.HS-LS3-2

Based your answer on the figure: A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?

• an accumulation of A and no production of B and C

• an accumulation of A and B and no production of C

Tags

NGSS.HS-LS3-2