Many eukaryotic genes contain a large number of exons. Correct splicing of such genes requires that neighboring exons be ligated to one another; if they are not, exons will be left out. One early proposal suggested that the splicing machinery bound to a splice site at one end of an intron and scanned through the intron to find the splice site at the other end. Such a scanning mechanism would guarantee that an exon was never skipped. This hypothesis was tested with one minigene with a duplicated 5ʹ splice site. Find diagram of the products you expect from minigene if the splicing machinery binds to a 5ʹ splice site and scans toward a 3ʹ splice site.

#Question id: 10983

#Unit 7. System Physiology – Animal

If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the AV bundle (bundle of His)?

#Question id: 1374

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to gap junctions.

i. Vertebrate gap junctions are composed of connexins, a family of structurally related transmembrane proteins with molecular weights between 26,000 and 60,000.

ii. Each vertebrate hexagonal particle consists of six noncovalently associated connexin molecules. Each individual connexin molecule has two membrane-spanning α helices with a topology similar to that of claudin.

iii. The permeability of gap junctions is regulated by posttranslational modification of connexins (e.g., phosphorylation) and is sensitive to changes in environmental conditions

such as intracellular pH and Ca2+ concentration, membrane potential, and the intercellular potential between adjacent interconnected cells (“voltage gating”).

iv. The assembly of connexins, their trafficking within cells, and the formation of functional gap junctions apparently depend on N-cadherin and its associated adapter proteins as well as desmosomal proteins.

Which of the following statements are correct?

#Question id: 23186

#Unit 13. Methods in Biology

#Question id: 23144

#Unit 13. Methods in Biology

#Question id: 15451

#Unit 4. Cell Communication and Cell Signaling