18 Regulation Of Gene Expression

Front 1

An ___ is a stretch of DNA consisting of an operator, a promoter, and genes for a related set of proteins, usually making up an entire metabolic pathway.

Back 1

operon

Front 2

The ___ is/are arranged sequentially after the promoter.

Back 2

Genes of an operon

Front 3

A ___ is a specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.

Back 3

promoter

Front 4

A ___ codes for a protein, such as repressor, that controls the transcription of another gene or group of genes

Back 4

regulatory gene

Front 5

5. Regulatory proteins bind to the ___ to control expression of the operon.

Back 5

operator

Front 6

A ___ is a protein that inhibits gene transcription. In prokaryotes, this protein binds to the DNA in or near the promoter.

Back 6

repressor

Front 7

An ___ is a specific small molecule that binds to a bacterial regulatory protein and changes its shape so that it cannot bind to an operator, thus switching an operon on.

Back 7

inducer

Front 8

What molecule binds to promoters in bacteria and transcribes the coding regions of the genes?

Back 8

RNA polymerase

Front 9

What is allosteric regulation?

Back 9

In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.

Front 10

Under which conditions are the lac structural genes expressed most efficiently?

Back 10

No glucose, high lactose

Front 11

What happens to the expression of the lacI gene if lactose is not available in the cell?

Back 11

There is no change—the lacI gene is constitutively expressed.

Front 12

Which of the following enzymes converts ATP to cAMP?

Back 12

Adenylyl cyclase

Front 13

Regulatory proteins bind to _____.

Back 13

the operator

Front 14

operon is not transcribed

Back 14

lac operon: lactose absent; trp operon: tryptophan present

Front 15

operon is transcribed, but not sped up by the positive control

Back 15

trp operon: tryptophan absent; lac operon: lactose present, glucose present

Front 16

operon is transcribed quickly through postive control

Back 16

lac operon: lactose present, glucose absent

Front 17

Negative control:When lactose is absent

Back 17

the repressor protein is active, and transcription is turned off.

Front 18

Negative control:When lactose is present

Back 18

the repressor protein is inactivated, and transcription is turned on.

Front 19

Positive control:When glucose is absent

Back 19

another regulatory protein (CAP) binds to the promoter of the lac operon, increasing the rate of transcription if lactose is present

Front 20

Modification of chromatin structure:Methylation of histone tails in chromatin can promote condensation of the chromatin.

T or F

Back 20

TRUE

Front 21

Modification of chromatin structure:DNA is not transcribed when chromatin is packaged tightly in a condensed form.

Back 21

TRUE

Front 22

Modification of chromatin structure:Some forms of chromatin modification can be passed on to future generations of cells.

Back 22

TRUE

Front 23

Modification of chromatin structure:Acetylation of histone tails is a reversible process

Back 23

TRUE

Front 24

An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter.

Back 24

This arrangement of genes is common in bacteria. For example, genes involved in lactose metabolism are clustered in the lac operon of E. coli, and genes involved in tryptophan metabolism are in the trp operon.

Front 25

What molecule binds to promoters in bacteria and transcribes the coding regions of the genes?

Back 25

RNA polymerase is the enzyme that binds to promoters and transcribes the coding regions of genes into RNA.

Front 26

What is allosteric regulation?

Back 26

In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.

Front 27

Which of the following enzymes converts ATP to cAMP?

Back 27

Adenylyl cyclase converts ATP to cAMP, which helps CAP bind and facilitates binding of RNA polymerase to the lac promoter.

Front 28

What is the function of a spliceosome?

Back 28

RNA processing

Front 29

histone acetylation

Back 29

acetyl groups are attached to positively charged lysines in histone tailsloosens chromatin structure, promotes initiation of transcription

Front 30

DNA Methylation:

Back 30

addition of methyl groups (methylation) can condense chromatin; Reduces transcription

Front 31

phosphorylation

Back 31

the addition of phosphate groups; next to a methylated amino acid can loosenchromatin

Front 32

DNA Methylation

Back 32

*DNA methylation inactivates genes *Methylation patterns are inherited

*Removal of methyl groups can turn on genes

*Methylation permanently regulates expression of certain maternal or paternal alleles at start ofdevelopment

Front 33

Regulation of Transcription Initiation

Back 33

Chromatin-modifying enzymes control gene expression by making a region of DNA either more orless able to bind the transcription machinery

Front 34

Activators

Back 34

(specific transcription factors) bind to enhancer DNA sequences and then to mediatorproteins.

Front 35

Bending of DNA by a protein enables _________ to influence a distant promoter.

Back 35

enhancers

Front 36

Alternative RNA splicing

Back 36

*Enables multiple mRNA’s from same transcript

*The primary transcript can be spliced in more than one way.

*The two mRNA's are translated into different but related muscle proteins

Front 37

mRNA Degradation

Back 37

Lifespan of mRNA determined by untranslated (UTR) regions at 3’ end of molecule

Front 38

Protein Processing

Back 38

May be needed to make a protein functionMay involve chemical modification of the protein before it will function

Front 39

Protein Degradation

Back 39

Regulates length of time that protein functions

Front 40

Regulation by Noncoding RNAs

Back 40

Play multiple roles in controlling gene expression

Front 41

microRNAs (miRNAs)

Back 41

About 22 nucleotides long

Bind to complementary mRNA

Associate with one or more proteins in a complex

Complex degrades target RNA or blocks its translation

Front 42

Small interfering RNAs (siRNAs)

Back 42

Similar size & function to miRNAs

Blocking gene expression by siRNAs is called RNA interference (RNAi)

Front 43

Chromatin Remodeling by ncRNAs

Back 43

Can change chromatin structureResponsible for X chromosome inactivationfemale mammals, prevents expression of genes on one of X chromosomesCan cause re-formation of highly condensed heterochromatin at the centromere ofeac chromatidafter DNA replication

Front 44

Proto-oncogenes

Back 44

code for proteins that stimulate normal cell growth & division

Front 45

Genetic changes convert these to _______ (cancer causing genes)

Back 45

Oncogenes
*Cancer affects cell cycle control

Front 46

_________ (rat sarcoma gene) mutation leads to excessive cell divisio

Back 46

ras gene

*Tumor suppressor genes inhibit abnormal cell division

*Mutation in Ras makes Ras abnormally active

Front 47

Mutant cell cycle stimulating pathway

Back 47

- Mutation makes Ras abnormally active, with or without growth factor bound to receptor

- leads to excessive cell division and cancer

Front 48

Excessive cell division (cancer)

Back 48

Tumor suppressor p53 gene stops cell cycle after DNA damage-p53 is known as “guardian angel of the genome”

Front 49

Multistep Cancer Development

Back 49

Involves somatic mutationsMutations accumulate over time (age)As you age, mutations accumulate, so older people tend to have more cancers

Front 50

DNA changes that can lead to cancer

Back 50

- One active oncogene (dominant)

- Mutation/loss of several tumor-suppressor genes (recessive)

Front 51

Inherited Predisposition

Back 51

- Breast cancer: mutation in BRCA1 or BRCA2 gene increases susceptibility

- DNA sequencing can detect these mutations

Front 52

Viruses associated with some 15% of human cancer cases

Back 52

- Epstein-Barr virus linked to Burkitt’s lymphoma- Papillomaviruses linked to cervical cancer

- HTLV-1 virus causes type of adult leukemia