Question

What is the first sugar derivative obtained in dark reactions of photosynthesis?

Answer 1

Photosynthesis has two major steps - Light dependent and Light independent reaction steps. 

Light independent reactions cycle is known as 'Dark Reactions' or 'Calvin Cycle' where products of light reaction are further utilized. 

In calvin cycle, 
1. Enzyme RuBisCo catalyses RuBP to form 3-PGA. This reaction utilizes CO2. 
2. Phosphoglycerate Kinase then catalyse phosporylation of 3-PGA to produce 1,3-Bisphosphogylcerate. 
3. 1,3 BPGA is then reduces by glyceraldehyde 3-phosphate dehydrogenase to produce Glyceraldehyde 3-phosphate. 

Thus, these phosphate molecules are the first sugar products/derivatives generated in Calvin Cycle or dark reaction. 

Attached is the textbook image of Calvin cycle for your reference.