The yeast Gal4 transcription activator comprises two domains: a DNA binding domain and an activation domain. The DNA-binding domain allows Gal4 to bind to appropriate DNA sequences located near genes that are required for metabolism of the sugar galactose. The activation domain binds to components of the transcriptional machinery (including RNA polymerase), attracting them to the promoter, so the regulated genes can be turned on. In the absence of Gal4, the galactose genes cannot be turned on. When Gal4 is expressed normally, the genes can be maximally activated. When Gal4 is massively overexpressed, however, the galactose genes are turned off. Choose correct explanation for this regulation?

A. In order for Gal4 to work properly, the DNA-bound Gal4 recruits many proteins, including RNA polymerase, to the promoter.

B. When there is too much Gal4 in the cell, the free and DNA-bound Gal4 will compete for the limited quantities of these other components.

C. In the presence of excess Gal4, those components are tied up in unproductive complexes with free Gal4, thereby preventing their recruitment to the promoter.

D. cells that massively overexpress Gal4 grow poorly because of the reduced availability of critical components of the transcription machinery.

E. Over concentration of Gal4 prevent suppressors to bind with DNA

#Question id: 10897

#Unit 10. Ecological Principles

When three species of sunfish with similar niches were all placed in the same experimental pond, each made use of resources that they did not exploit in the absence of the other species. This scenario is referred to as

#Question id: 10898

#Unit 10. Ecological Principles

Living in groups, such as the herds of bison that once inhabited the prairie, may evolve because of

#Question id: 10899

#Unit 6. System Physiology – Plant

Companion cells transport of photosynthetic products from producing cells in mature leaves to the sieve elements in the minor veins of the leaf. There are at least three different types of companion cells in the minor veins of mature, exporting leaves, All three cell types have dense cytoplasm and abundant mitochondria;

#Question id: 10900

#Unit 6. System Physiology – Plant

companion cells in minor veins of mature leaves. All three cell types have dense cytoplasm and abundant mitochondria, there are three types companion cells  present in column A while its characteristics given in column B;

             COLUMN A                                                               COLUMN B

A) Ordinary companion cells             i) appear well suited for taking up solutes via cytoplasmic connections numerous plasmodesmata connecting them to bundle sheath cells. Its having numerous small vacuoles, as well as poorly developed thylakoids.

B) Transfer cells                                 ii) have chloroplasts with well-developed thylakoids     and a cell wall with a smooth inner surface. The number of plasmodesmata connecting ordinary companion cells to surrounding cells.

 C) Intermediary cells                          iii) the development of fingerlike wall in growths, particularly on the cell Walls. These wall ingrowths greatly increase the surface area of the transfer cell’s  plasma membrane, few plasmodesmata connect this type of companion cell to any of the surrounding cells except its own sieve element.

Which of the following correct combination;

#Question id: 10901

#Unit 6. System Physiology – Plant

P-proteins have been characterized at the molecular level. P-proteins from the genus Cucurbita consist of two major proteins;

#Question id: 10902

#Unit 6. System Physiology – Plant

P-proteins from the genus Cucurbita consist of two major proteins: PP1, the phloem filament protein, and PP2, the phloem lectin. Both PP1 and PP2 are thought to be synthesized in_______A___________and transported via the_______B_________to the_______C______, where they associate to form P-protein filaments and P-protein bodies.