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The study of molecular biology requires approaches of both in vivo and in vitro models. These have helped to demonstrate the expression of genes, their inheritance, and the nature of mutations. What is the difference between an in vivo and an in vitro model? What are examples of each?

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Elin Hessel
Elin HesselLv2
28 Sep 2019

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Related questions

"The genes transcribed by RNA polymerase III (pol III) generally have intragenic promoter elements. One of them, the yeast U6 snRNA (SNR6) gene is activated in vitro by a positioned nucleosome between its intragenic box A and extragenic, downstream box B separated by approximately 200 bp. We demonstrate here that the in vivo chromatin structure of gene is characterized by the presence of an array of positioned nucleosomes, with only one of them in the 5' end of the gene having a regulatory role. A positioned nucleosome present between the boxes A and B in vivo does not move when the gene is repressed due to nutritional deprivation. In contrast, the upstream nucleosome which covers the TATA box under repressed condition; is shifted approximately 50 bp upstream by an ATP-dependent chromatin remodeler RSC upon activation. It is marked with histone variant H2A.Z and H4K16 acetylation in active state. In the absence of H2A.Z, the chromatin structure of the gene does not change, suggesting H2A.Z is not required for establishing the active chromatin structure. These results show that the chromatin structure directly participates in regulation of a pol III-transcribed gene under different states of its activity in vivo."

Q1: Explain how the FACT protein might deal with the positioned nucleosome between BoxA and Box B during transcription?

Q2: In general, what effect does histone acetylation have on transcription?

The second experiment is described in the following abstract:

Successful reprogramming of differentiated human somatic cells into a pluripotent state would allow creation of patient- and disease-specific stem cells. We previously reported generation of induced pluripotent stem (iPS) cells, capable of germline transmission, from mouse somatic cells by transduction of four defined transcription factors. Here, we demonstrate the generation of iPS cells from adult human dermal fibroblasts with the same four factors: Oct3/4, Sox2, Klf4, and c-Myc. Human iPS cells were similar to human embryonic stem (ES) cells in morphology, proliferation, surface antigens, gene expression, epigenetic status of pluripotent cell-specific genes, and telomerase activity. Furthermore, these cells could differentiate into cell types of the three germ layers in vitro and in teratomas. These findings demonstrate that iPS cells can be generated from adult human fibroblasts.

What does this tell you about the nature of the changes that take place during the process of differentiation? How would you think that the reactivation of these genes might act?

1-What are the advantages and disadvantages of using molecular cloning techniques for purification of proteins? If the desired function is to study in vivo function of a protein, what protein expression system would you use and why?

2-What are the optimization conditions you will have to establish before the purification of a protein and why these optimizations necessary?

3-What are some of the protein monitoring techniques used during protein purification? What is the principle behind each of the techniques you have listed?

4-What is the principle behind molecular permeation chromatography? Give salient features of gel permeation chromatography

5-You have been given a mixture of hemoglobin (Mr. 72 kDa) and cytochrome c (Mr 13.5 kDa), and Sepadex beads (G10, G25 and G75). You have separate and purify these proteins by gel permeation chromatography. Suggest an experimental protocol as to how you would purify them?

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