TLS Online TPP Program

#Question id: 10858


Which of the following is an example of obligatory symbiotic mutualism?

#Unit 10. Ecological Principles
  1. Myxomatosis and rabbits
  2. Mycorrhizae
  3. Attine ants and the fungus they culture
  4. Truffles and small mammals 
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TLS Online TPP Program

#Question id: 4536

#Unit 3. Fundamental Processes

The human b-interferon gene is activated in cells upon viral infection through some activators, EXCEPT one

TLS Online TPP Program

#Question id: 4537

#Unit 3. Fundamental Processes

The enhancer DNA is __, but once the activators are bound it is relatively  , HMGA1 the DNA and thus helps the final structure form.

TLS Online TPP Program

#Question id: 4538

#Unit 3. Fundamental Processes

We first consider a generic case. Gene A is controlled by four signals (1, 2, 3, and 4), each working through a separate activator (activators 1, 2, 3, and 4). Gene B is controlled by three signals (3, 5, and 6), working through activators 3, 5, and 6. It shows-

TLS Online TPP Program

#Question id: 4539

#Unit 3. Fundamental Processes

The yeast S. cerevisiae exists in three forms: two haploid cells of different mating types—a and alpha and the diploid formed when an a and an a cell mate and fuse. The a cell and the a cell each encodes cell-type-specific regulators: a cells make the regulatory protein a1, and alpha cells make the proteins alpha1 and alpha2. A fourth regulatory protein, called Mcm1, is also involved in regulating the mating-type-specific genes (and many other genes) and is present in both cell types which shows Combinatorial Control.

The arrangement of regulators at the promoters of a-specific genes and a-specific genes is

cell type:

gene regulatory proteins:

target genes:

1.a cell (haploid)

a1

Mcm1

aSG

alphaSG

2.αlpha cell (haploid)

alpha 1

alpha 2

Mcm2

hSG

3.a/αlpha cell (diploid)

a1

Mcm2

alpha2

TLS Online TPP Program

#Question id: 4540

#Unit 3. Fundamental Processes

Transcription of eukaryotic genes can be repressed in various ways. These include the four mechanisms

1. Competition

a-Repression is caused by recruiting histone modifiers that alter nucleosomes in ways that inhibit transcript

2. Inhibition

b-A repressor binds to a site on DNA beside an activator and interacts with that activator, occluding its activating region

3. Direct repression

c-By binding to a site on DNA that overlaps the binding site of an activator, a repressor can inhibit binding of the activator to a gene and thus block activation of that gene.

4. Indirect repression

d-A repressor binds to a site upstream of a gene and, by interacting with the transcriptional machinery at the promoter in some specific way, inhibits transcription initiation.


TLS Online TPP Program

#Question id: 4541

#Unit 3. Fundamental Processes

Mig1 recruits a “repressing complex” containing the Tup1 protein. This complex is recruited by many yeast DNA-binding proteins that repress transcription, including the alpha2 protein involved in controlling the mating-type specific. Tup1 also has counterparts in mammalian cells, choose correct mechanisms have been proposed to explain the repressing effect of Tup1.

I-Tup1 acts on nucleosomes either through recruiting histone deacetylases and/or by positioning a nucleosome at or near the transcription start site.

II-Tup1 interacts directly with the transcriptional machinery at the promoter and inhibits initiation.