MEDizzy - A study of peripheral blood smears shows that neutrophil

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The Cell as a Unit of Health and Disease

A study of peripheral blood smears shows that neutrophil nuclei of women have a Barr body, whereas those of men do not. The Barr body is an inactivated X chromosome. Which of the following forms of RNA is most likely to play a role in Barr body formation?

ExplanationThere are forms of noncoding RNA that play a role in gene expression. Long noncoding RNA (lncRNA) segments greater than 200 nucleotides in length can bind to chromatin to restrict access of RNA polymerase to coding segments. The X chromosome transcribes XIST, a lncRNA that binds to and represses X chromosome expression. However, not all genes on the “inactive” X chromosome are switched off. The RNA transcribed from nuclear DNA that directs protein synthesis through translation is mRNA. MicroRNAs (miRNAs) are noncoding RNA sequences that inhibit the translation of mRNAs. Gene-silencing RNAs (small interfering RNAs [siRNAs]) have the same function as miRNAs, but they are produced synthetically for experimental purposes.