) Fig. 6.10, the blue curve suggests high level of transcription initiation for that set of samples. Why did it increase? Q1B) In the same figure, the data for the green curve was obtained with a so-called rifampicin-resistant core. You would expect that the green curve should overlap with the blue one, but it doesn’t. What is the reason?
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
Q1A) Fig. 6.10, the blue curve suggests high level of transcription initiation for that set of samples. Why did it increase?
Q1B) In the same figure, the data for the green curve was obtained with a so-called rifampicin-resistant core. You would expect that the green curve should overlap with the blue one, but it doesn’t. What is the reason?
![RNA chain initiation
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Figure 6.10 Sigma can be reused. Travers and Burgess allowed
RNA polymerase holoenzyme to initiate and elongate RNA chains on a
T4 DNA template at low ionic strength, so the polymerases could not
dissociate from the template to start new RNA chains. The red curve
shows the initiation of RNA chains, measured by [y-³2PJATP and
[y-³2P]GTP incorporation, under these conditions. After 10 min (arrow),
when most chain initiation had ceased, the investigators added new,
rifampicin-resistant core polymerase in the presence (green) or
absence (blue) of rifampicin. The immediate rise of both curves
showed that addition of core polymerase can restart RNA synthesis,
which implied that the new core associated with o that had been
associated with the original core. In other words, the σ was recycled.
The fact that transcription occurred even in the presence of rifampicin
showed that the new core, which was from rifampicin-resistant cells,
together with the old σ, which was from rifampicin-sensitive cells,
could carry out rifampicin-resistant transcription. Thus, the core, not
the σ, determines rifampicin resistance or sensitivity. (Source: Adapted
from Travers, A.A. and R.R. Burgess, "Cyclic re-use of the RNA polymerase sigma
factor." Nature 222:537-40, 1969.)](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F52c45e04-d5ce-4e44-ac1a-e4d0e6ebe50f%2F0d4f975c-46d7-4b96-8967-f47c3177e2dc%2Fp13syml_processed.png&w=3840&q=75)
The enzyme RNA polymerase has following subunits in its core enzyme- 1 beta (β), 1 beta prime (β'), 2 alpha (α) and 1 omega (ω). Holoenzymes, is formed when a Sigma factor combines with the core enzyme.
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