Please Mark correct answer of the multiple choice questions

Please, Mark correct answer of the multiple choice questions. Select only one answer, if any other indications are not present in the question. Write 2-3 sentences of explanation, why you selected this particular answer, or answer specific question if indicated.

1) Histone deacylase modulate gene transcription. Which sentence is incorrect?

A. HDAC removes acetyl group from histone’s lysine

B. HDAC has opposite effect to HAT

C. HDAC condensates chromatin and prevent transcription

D. HDAC decreases ability of histones to bind DNA

Explain:

2) In the absence of -mercaptoethanol (non-reduced conditions) protein migrate on SDS-PAGE with molecular weight approx. 90 kDa. In the presence of -mercaptoethanol (reduced conditions) on the gel appeared only one band in molecular weight resembled to 15 kDa. Which sentence described the best structure of this protein?

A. This could be only homohexamer

B. This could be only heterohexamer

C. This could be only homoheptamer

D. This could be homohexamer or heterohexamer

Explain:

Solution

1) Histone deacylase modulate gene transcription. Which sentence is incorrect?

the correct answer is A. HDAC removes acetyl group from histone’s lysine

Because histone deacetylases (HDACs) and acetyltransferases (HATs) regulate gene expression by removal or addition, of acetyl groups to -amino groups in lysine residues of core nucleosomal histones. Increased histone acetylation attenuates their electrostatic interaction with the negatively charged DNA backbone, promotes unfolding of the histone–DNA complex, and modulates access of transcription factors to their sites of action and transcription of their target genes . Normal cell differentiation and function require coordinated gene transcription and appropriate balance of HAT and HDAC activities.

2) In the absence of -mercaptoethanol (non-reduced conditions) protein migrate on SDS-PAGE with molecular weight approx. 90 kDa. In the presence of -mercaptoethanol (reduced conditions) on the gel appeared only one band in molecular weight resembled to 15 kDa. Which sentence described the best structure of this protein?

The correct answer is B. This could be only heterohexamer

because No real limitations as to the size of structures. X-rays are scattered by electrons – the amount of scattering is proportional to the number of electrons.Interference between X-rays that are scattered from atoms in different locations change the amplitude and the phase of the scattered X-rays. Therefore, scattered X-rays can be used to determine the position of atoms.