Splice sites are directional in nature. 5’ splice site -the left, or donor, site and the 3’ splice site - right, or acceptor, site. 

1. U2 addition to base pair with the branch site in the presence of ATP

2. U1 and U4 release Formation of the catalytic center in which U6 base pairs with the 5' splice site; U6 also base pairs with U2; U2 remains base paired with the branch site; U5 interacts with both exons through its loop.

So, 1 and 2 are the event of complex formation which are 

#Question id: 4213

#Unit 3. Fundamental Processes

Which statement describes the correct order of events in prokaryotic translation initiation?

#Question id: 10603

#Unit 10. Ecological Principles

The population size of a bird increased from 600 to 700 in one year. If the per capita birth rate of this population is 0.50, what is its per capita death rate?

#Question id: 5315

#Unit 11. Evolution and Behavior

In humans, the embryonic and fetal forms of hemoglobin have a higher affinity for oxygen than that of adults. Why is this the case?

#Question id: 45

#Unit 1. Molecules and their Interaction Relevant to Biology

What is the standard free-energy change, ΔG°, under physiological conditions (E. coli grows in the human gut, at 37 °C) for the following reaction? (Keq = 7.8 × 10^2)

Glucose + ATP → glucose 6-phosphate + ADP

#Question id: 4268

#Unit 3. Fundamental Processes

23S rRNA catalyze peptide-bond formation as

A. base pairing between the 23S rRNA and the CCA ends of the tRNAs

B. A- and P-sites positions the a-amino group of the aminoacyl-tRNA to attack the carbonyl group of the growing polypeptide attached to the peptidyl-tRNA

C. Entropic catalysis is involved