#Question id: 3820
#Unit 3. Fundamental Processes
Meselson and Stahlʹs experiments involved growing E. coli on a medium containing 15N (heavy nitrogen) which increased the density of the bacterial DNA. Cells were then grown on a medium containing only 14N. DNA samples were obtained for analysis after one, two and three rounds of replication (generations) and centrifuged on a density gradient. The double-helical DNA forms bands in the gradient depending on its density. How many bands did Meselson and Stahl see after two generation of cells were grown on the 14N medium?
#Question id: 4558
#Unit 3. Fundamental Processes
Classes of RNA transcribed by the three eukaryotic nuclear RNA Polymerase;
|
Polymerase |
RNA Transcribed |
|
A. RNA polymerase I | i) tRNAs, 5S rRNA, snRNA, U6, 7S RNA |
|
B. RNA polymerase II |
ii) Pre-rRNA 28S, 18SrRNA, 5.8SrRNAs |
|
C. RNA polymerase III |
iii) mRNA, snRNAs, siRNAs, miRNAs |
Match the following correct combination given above combinations;
#Question id: 2906
#Unit 2. Cellular Organization
A closer look at the interactions between the histones and the nucleosomal DNA reveals the structural basis for the binding and bending of the DNA within the nucleosome. Fourteen distinct sites of contact are observed, one for each time the minor groove of the DNA faces the histone octamer. State whether the following set of statements is true/false regarding this association?
I. The majority of these associations are between the proteins and the oxygen atoms in the phosphodiester backbone near the minor groove of the DNA.
II. The association of DNA with the nucleosome is mediated by a large number (about 40) of hydrogen bonds between the histones and the DNA.
III. Maximum numbers of hydrogen bonds are made between the protein side chains and the bases, and all of these are made in the minor groove of the DNA.
IV. The highly basic nature of the histones further facilitates DNA bending by masking the negative charge of the phosphates that ordinarily resists DNA bending.
V. The positively charged nature of the histones facilitates the close juxtaposition of the two adjacent DNA helices necessary to wrap the DNA more than once around the histone octamer.
#Question id: 1187
#Unit 4. Cell Communication and Cell Signaling
Which protein stabilizes an intermediate in the Ras GTP hydrolysis reactions?
#Question id: 11544
#Unit 7. System Physiology – Animal
When a steroid hormone and a polypeptide hormone exert similar effects on a population of target cells, then ________.