Chapter 8 Flashcards by Mia Sassano

All of the cell types that make up an organism
share the same

genome

How well did you know this?

Not at all

Perfectly

enables cells to selectively
control the synthesis of the RNAs and proteins in
their genome

gene expression

How well did you know this?

Not at all

Perfectly

First step of gene expression:

Transcriptional control

How well did you know this?

Not at all

Perfectly

Control the rate at which DNA is
transcribed into mRNA is what step in gene expression

1st, transcriptional control

How well did you know this?

Not at all

Perfectly

This is the most efficient (but slowest) way to control gene expression is through

transcriptional control

How well did you know this?

Not at all

Perfectly

Transcription is initiated at the

promoter

How well did you know this?

Not at all

Perfectly

The __ is located upstream of (a.k.a. before) the starting
point for RNA synthesis

promoter

How well did you know this?

Not at all

Perfectly

What must bind to the promoter to begin transcription

RNA polymerase

How well did you know this?

Not at all

Perfectly

most genes include ___
that are used to switch the gene on or off

regulatory DNA sequences

How well did you know this?

Not at all

Perfectly

Regulatory DNA sequences are bound by proteins called

transcription regulators

How well did you know this?

Not at all

Perfectly

Each transcription regulator recognizes __, and regulates __

different DNA sequences, distinct genes

How well did you know this?

Not at all

Perfectly

Most transcription regulators fit into the __ of the DNA
double helix and form ___ in the groove

major groove, contacts with the nucleotide pairs

How well did you know this?

Not at all

Perfectly

Each individual contact with the transcription regulators and nucleotide pairs is __

weak

How well did you know this?

Not at all

Perfectly

How many contacts form between the protein and the DNA so the interaction is strong and specific

10-20

How well did you know this?

Not at all

Perfectly

Regulatory DNA sequences are found where? located where?

found in nearly all genes, located near to or in promoters

How well did you know this?

Not at all

Perfectly

Transcription regulators bind to

DNA sequences

How well did you know this?

Not at all

Perfectly

Transcription regulators can act as

activators or repressors by switching the gene on or off

How well did you know this?

Not at all

Perfectly

transcription regulators regulate binding of

RNA polymerase to the promoter

How well did you know this?

Not at all

Perfectly

use simple switches to control gene expression in response to their environment

bacteria

How well did you know this?

Not at all

Perfectly

Genes that encode proteins that work together are often clustered together on the chromosome and transcribed from a

single promoter

How well did you know this?

Not at all

Perfectly

gene clusters are called

operons

How well did you know this?

Not at all

Perfectly

Operons are common in __ but rare in __

bacteria, eukaryotes

How well did you know this?

Not at all

Perfectly

The tryptophan operon (a.k.a. Trp operon) __that synthesize tryptophan

contains five genes that
encode enzymes

How well did you know this?

Not at all

Perfectly

The tryptophan repressor regulates

expression
of the Trp operon

How well did you know this?

Not at all

Perfectly

The operon’s promoter sequence contains a regulatory sequence called the

operator

If tryptophan is ___ there's no need to synthesize more

already available

The tryptophan repressor binds the operator only if....

it is also bound to tryptophan

What occurs in the absence of tryptophan...

Trp repressor is inactive and does not bind the operator, so transcription can proceed

When the tryptophan repressor is bound to the operator....

it blocks access of RNA polymerase to the promoter, preventing transcription of the operon

The Lac operon is controlled by two transcription regulators:

activator and repressor

The Lac operon is turned on in the absence of __ and the presence of __

glucose, lactose

The Lac operon encodes proteins necessary to import and digest

lactose

The Lac operon is controlled by the

CAP activator and Lac repressor

When glucose is not available, the bacterium makes

cAMP, which binds to CAP activator

The CAP activator must bind

cAMP to bind DNA

Lactose (or allolactose) binds the

Lac repressor and prevents it from binding DNA

The Lac repressor only binds DNA in the

absence of lactose

To activate gene expression, the CAP activator must __ and the lac repressor must __

bind DNA, not bind DNA

Eukaryotic transcription regulators control gene expression...

from a distance

Eukaryotic gene activators bind DNA sites called

enhancers

The DNA between the enhancer and the promoter forms a

loop to bring the activator protein close to the promoter

The most important adaptor is a large protein complex called the

Mediator

positions the general transcription factors and RNA polymerase at the promoter

mediator complex

Histone acetyltransferases attach

acetyl groups to histones

Acetyl groups recruit

transcription activators

uses ATP to alter the arrangement of nucleosomes on the DNA

Chromatin-remodeling complex

Transcription regulators work together to

regulate gene expression

Dozens of __ bind regulatory sequences that can be spread over thousands of nucleotides

transcriptional regulators

A single transcription regulator can coordinate the expression of

many genes

A master transcription regulator that controls eye development

controls expression of multiple genes by binding regulatory DNA sequences

Some genes controlled by Ey encode

additional transcription regulators

Ey is so powerful that it can

activate its regulatory network outside its normal location

Differentiated cells maintain their identity through

“cell memory” mechanisms

After a cell is differentiated into a particular cell type, its progeny cells

will remain the same cell type

To maintain cell identity, the pattern of gene expression must be

passed onto daughter cells

3 mechanisms of cell memory

- Positive feedback loops • DNA methylation • Histone modifications

Transmission of gene expression patterns to daughter cells without change in DNA sequence

Epigenetic inheritance

In positive feedback loops, the transcription factor...

activates its own gene

Each time e the cell divides, the transcription factor is distributed to both daughter cells, so it continues to stimulate the

positive feedback loop

DNA methylation occurs on many __, but only those __

cytosines, adjacent to guanine

Inhibits gene expression by recruiting transcriptional repressors

DNA methylation

Important for maintaining distinct cell types

DNA methylation

Following DNA replication, methylated cytosines act as molecular tags that recruit

maintenance methyltransferase

maintenance methyltransferase ensures that the

same methylation pattern is copied to the new DNA strand

With histone modifications, each daughter cell inherits

half of its parent’s histone proteins

bind modified histone tails and confer the same modifications to neighboring histones

enzymes

Cells can exert post-transcriptional control by controlling

RNA and protein stability and lifetime

can be regulated by sequences in the untranslated regions

mRNA stability and translation

Nucleotide sequences in the untranslated regions of mRNA contain

binding sites for proteins involved in RNA degradation

In prokaryotes, the ribosome-binding site is a common target of

regulation

control the expression of thousands of genes

miRNAs

miRNAs are packaged with specialized proteins to form a

RISC complex

RISC stands for

RNA-induced silencing complex

miRNAs base-pair with

mRNAs with complementary sequences

Once an mRNA base-pairs with a miRNA, it is

degraded or translation is blocked

destroy foreign RNAs through RNA interference

siRNA

eukaryotic protein complex capable of degrading damaged, misfolded or un-needed proteins

Proteasome

a small protein tag, gets covalently attached to of the target protein

Ubiquitin

Ubiquitinated proteins are degraded by

proteases

When the concentration of tryptophan inside the cell is high: (a) the tryptophan repressor is activated (b) the tryptophan repressor is inactivated AND therefore… (c) transcription of the tryptophan operon is allowed (d) transcription of the tryptophan operon is shut down

A, d

In which conditions will the lac operon be switched ON?

Glucose absent, lactose present; CAP activator is bound to cAMP, lac repressor bound to allolactose