Post-transcriptional modifications — MCQs

An investigator is developing a drug for muscle spasms. The drug inactivates muscular contraction by blocking the site where calcium ions bind to regulate actin-myosin interaction. Which of the following is the most likely site of action of this drug?

A 25-year-old female comes to the clinic complaining of fatigue and palpitations. She has been undergoing immense stress from her thesis defense and has been extremely tired. The patient denies any weight loss, diarrhea, cold/heat intolerance. TSH was within normal limits. She reports a family history of "blood disease" and was later confirmed positive for β-thalassemia minor. It is believed that abnormal splicing of the beta globin gene results in β-thalassemia. What is removed during this process that allows RNA to be significantly shorter than DNA?

An investigator studying protein synthesis in human stem cells isolates tRNA molecules bound to mRNA molecules. The isolated tRNA molecules have inosine in the 5' position of the anticodon; of these, some are bound to adenine, some to cytosine, and some to uracil at the 3' position of the mRNA codon. Which of the following properties of the genetic code is best illustrated by this finding?

A 25-year-old woman presents into the clinic complaining of worsening malaise, hair loss, and a rash on her face. The patient states that she has been avoiding daylight because the rash becomes painful, and she has not been able to go to classes because of debilitating arthralgia in her fingers and ankles. No significant past medical history. She takes no medication. At the time of the consult, the patient has a fever of 39.0°C (102.2 °F). The presence of which of the following is most commonly seen on diagnostic labs in this patient’s most likely condition?

An investigator is studying the crossbridge cycle of muscle contraction. Tissue from the biceps brachii muscle is obtained at the autopsy of an 87-year-old man. Investigation of the muscle tissue shows myosin heads attached to actin filaments. Binding of myosin heads to which of the following elements would most likely cause detachment of myosin from actin filaments?

A 30-year-old African American woman develops a facial rash in a "butterfly" pattern over her face and complains of feeling tired and achy in her joints. In the course of a full rheumatologic workup you note that she has anti-snRNP antibodies. Which of the following do snRNPs affect?

An investigator is studying the genotypes of wingless fruit flies using full exome sequencing. Compared to wild-type winged fruit flies, the wingless fruit flies are found to have a point mutation in the gene encoding wing bud formation during embryogenesis. The point mutation in the gene causes the mRNA transcript to have a 'UUG' segment instead of an 'AUG' segment. Which of the following processes is most likely affected by this mutation?

An investigator is studying the function of the endoplasmic reticulum in genetically modified lymphocytes. A gene is removed that facilitates the binding of ribosomes to the endoplasmic reticulum. Which of the following processes is most likely to be impaired as a result of this genetic modification?

E. coli has the ability to regulate its enzymes to break down various sources of energy when available. It prevents waste by the use of the lac operon, which encodes a polycistronic transcript. At a low concentration of glucose and absence of lactose, which of the following occurs?

Expression of an mRNA encoding for a soluble form of the Fas protein prevents a cell from undergoing programmed cell death. However, after inclusion of a certain exon, this same Fas pre-mRNA eventually leads to the translation of a protein that is membrane bound, subsequently promoting the cell to undergo apoptosis. Which of the following best explains this finding?