Lesson test: Choosing what to make

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Choosing what to make

1.[2p]
What did Monod's diauxic growth curve show?

E. coli uses glucose first, then pauses, then adapts to lactose

Correct

E. coli uses lactose and glucose at the same rate

The answer is: *E. coli* uses glucose first, then pauses, then adapts to lactose

E. coli cannot grow on lactose at all

The answer is: *E. coli* uses glucose first, then pauses, then adapts to lactose

Bacterial growth is always exponential

The answer is: *E. coli* uses glucose first, then pauses, then adapts to lactose

2.[3p]
A cell with a mutated operator expresses its operon constitutively, and adding a good copy of the whole region on a plasmid does not fix the chromosomal operon. What does that make the operator?

A cis-acting site, since it affects only the DNA it is part of

Correct

A trans-acting product, since it is diffusible

The answer is: A cis-acting site, since it affects only the DNA it is part of

A repressor protein

The answer is: A cis-acting site, since it affects only the DNA it is part of

An RNA polymerase subunit

The answer is: A cis-acting site, since it affects only the DNA it is part of

3.[2p]
The lac repressor is a trans-acting product, so a working copy supplied on a plasmid restores regulation of the chromosomal operon.

True

Correct

False

The answer is: True

4.[2p]
The lactose operon transcribes only when lactose is present and glucose is absent. What logical function is that?

AND

Correct

The answer is: AND

NOT

The answer is: AND

Exclusive OR

The answer is: AND

5.[3p]
Why does the operon use a weak promoter plus an activator rather than a strong promoter plus a repressor alone?

A repressor sometimes dissociates, so a weak promoter lowers the leak while the activator restores full output when wanted

Correct

Activators are cheaper to make than repressors

The answer is: A repressor sometimes dissociates, so a weak promoter lowers the leak while the activator restores full output when wanted

Strong promoters cannot be repressed at all

The answer is: A repressor sometimes dissociates, so a weak promoter lowers the leak while the activator restores full output when wanted

RNA polymerase cannot bind strong promoters in bacteria

The answer is: A repressor sometimes dissociates, so a weak promoter lowers the leak while the activator restores full output when wanted

6.[3p]
The lac repressor associates with its operator faster than three-dimensional diffusion allows. What is the accepted explanation?

It binds DNA non-specifically and slides along it, so each collision scans a stretch rather than a point

Correct

The measurement was in error

The answer is: It binds DNA non-specifically and slides along it, so each collision scans a stretch rather than a point

The operator moves towards the repressor

The answer is: It binds DNA non-specifically and slides along it, so each collision scans a stretch rather than a point

The repressor is present at far higher concentration than assumed

The answer is: It binds DNA non-specifically and slides along it, so each collision scans a stretch rather than a point

7.[3p]
Match each layer of eukaryotic regulation to what it does.

Nucleosomes
Histone acetylation
DNA methylation at CG sites
Enhancers

package DNA so that the default state of a gene is inaccessible
act from far away by looping the intervening DNA
marks promoters for silence and is copied through division
neutralises lysine charge and loosens the grip on DNA

Show the answer

Nucleosomes: package DNA so that the default state of a gene is inaccessible Histone acetylation: neutralises lysine charge and loosens the grip on DNA DNA methylation at CG sites: marks promoters for silence and is copied through division Enhancers: act from far away by looping the intervening DNA

8.[3p]
Which results show that differentiation does not remove genetic material?

Select all that apply

Gurdon's transplanted intestinal cell nuclei produced whole fertile frogs

Correct

Dolly the sheep was cloned from an adult cell

Correct

Four transcription factors reprogrammed adult fibroblasts to pluripotency

Correct

Mature red blood cells eject their nuclei

The answer is: Gurdon's transplanted intestinal cell nuclei produced whole fertile frogs, Dolly the sheep was cloned from an adult cell, Four transcription factors reprogrammed adult fibroblasts to pluripotency

9.[2p]
Why is a calico cat almost always female?

The coat colour gene is on the X, one X is inactivated at random early in development, and each patch is a clone of one such cell

Correct

Only females carry the pigment gene

The answer is: The coat colour gene is on the X, one X is inactivated at random early in development, and each patch is a clone of one such cell

Male cats cannot inherit two coat colour alleles from one parent

The answer is: The coat colour gene is on the X, one X is inactivated at random early in development, and each patch is a clone of one such cell

Coat colour is determined by mitochondrial DNA

The answer is: The coat colour gene is on the X, one X is inactivated at random early in development, and each patch is a clone of one such cell

1.[2p] What did Monod's diauxic growth curve show?

2.[3p] A cell with a mutated operator expresses its operon constitutively, and adding a good copy of the whole region on a plasmid does not fix the chromosomal operon. What does that make the operator?

3.[2p] The lac repressor is a trans-acting product, so a working copy supplied on a plasmid restores regulation of the chromosomal operon.

4.[2p] The lactose operon transcribes only when lactose is present and glucose is absent. What logical function is that?

5.[3p] Why does the operon use a weak promoter plus an activator rather than a strong promoter plus a repressor alone?

6.[3p] The lac repressor associates with its operator faster than three-dimensional diffusion allows. What is the accepted explanation?

7.[3p] Match each layer of eukaryotic regulation to what it does.

8.[3p] Which results show that differentiation does not remove genetic material?

9.[2p] Why is a calico cat almost always female?

1.[2p]
What did Monod's diauxic growth curve show?

2.[3p]
A cell with a mutated operator expresses its operon constitutively, and adding a good copy of the whole region on a plasmid does not fix the chromosomal operon. What does that make the operator?

3.[2p]
The lac repressor is a trans-acting product, so a working copy supplied on a plasmid restores regulation of the chromosomal operon.

4.[2p]
The lactose operon transcribes only when lactose is present and glucose is absent. What logical function is that?

5.[3p]
Why does the operon use a weak promoter plus an activator rather than a strong promoter plus a repressor alone?

6.[3p]
The lac repressor associates with its operator faster than three-dimensional diffusion allows. What is the accepted explanation?

7.[3p]
Match each layer of eukaryotic regulation to what it does.

8.[3p]
Which results show that differentiation does not remove genetic material?

9.[2p]
Why is a calico cat almost always female?