Practice Questions

TLS Online TPP Program

#Question id: 2888

Repressive complexes have been discovered that are composed of multiple repressing proteins bound to RNAs many kilobases in length that do not contain long open reading frames and are consequently called long noncoding RNAs or lncRNAs. Which of the following statements is correct regarding the regulation of these lncRNAs?

#Unit 2. Cellular Organization

X inactivation is controlled by a roughly 100-kb domain on the X chromosome called the X-inactivation center that encodes a lncRNA known as XIST that is responsible for inactivation of the maternally derived chromosome.
Depletion of a 2.2-kb noncoding RNA expressed from the HOXC locus by siRNA unexpectedly led to derepression of the HOXD locus, a roughly 40-kb region on another chromosome encoding several Hox proteins and multiple other noncoding RNAs, in these cells.
HOTTIP lncRNA, which is transcribed from the 5’end of the HOXA locus, is proposed to coordinate the activation of HOXA genes by binding to a histone H3 lysine 9 methylase represents the cis activation by lnc-RNAs.
In humans, but not in mice, a lncRNA called XACT has been discovered to associate with multiple sites along the full length of the active X chromosome and is postulated to contribute to repression of gene activity on that chromosome.

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TLS Online TPP Program

#Question id: 4660

#Unit 3. Fundamental Processes

Two-component system regulating response to low Gln,

a) Glutamine dissociates from the sensor domain in the NtrB protein, leading to activation of a histidine kinase transmitter domain in NtrB

b) glutamine binds to a sensor domain of NtrB, causing a conformational change in the protein that inhibits its histidine kinase activity, the regulatory domain of NtrC blocks its DNA-binding domain from binding the glnA enhancers.

c) Activated transmitter domain of NtrB that transfers the γ-phosphate of ATP to a histidine residue (H), this phosphohistidine then transfers the phosphate to an aspartic acid residue (D) in the NtrC protein

d) This causes a conformational change in NtrC that unmasks the NtrC DNA-binding domain so that it can bind to the glnA enhancers

Which of the following combination is correct?

TLS Online TPP Program

#Question id: 13108

#Unit 13. Methods in Biology

With the help of DNA fingerprinting which can be used to determine paternity. There are three babies (Baby A, Baby B and Baby C) in a maternity ward, and three sets of confused and worried parents. (Father and Mother #1 are a couple, as are Father and Mother #2, and Father and Mother #3.)

You do each PCR reaction on chromosome 15 and load each one into a separate well of an agarose gel, and then run the gel.

Why is it that some people show three bands?

TLS Online TPP Program

#Question id: 10815

#Unit 10. Ecological Principles

The evolution of two interacting species in a community is referred to as ________________.