# DBT JRF 2020 — Question 53

Exam: DBT JRF 2020 · Section: B · Topic: Biochemistry · Difficulty: Hard

## Question

Two proteins of molecular weights $1.0 \times 10^5$ and $1.0 \times 10^4$ Daltons were eluted from a gel filtration column at 220 ml and 300 ml respectively. The molecular weight of an unknown protein that elutes at 140 ml under the same conditions, will be

## Options

- **A.** $1.00 \times 10^6$
- **B.** $1.00 \times 10^5$
- **C.** $5.00 \times 10^6$
- **D.** $5.00 \times 10^5$

## Answer

Option A

## Explanation

Auxin (IAA — indole-3-acetic acid) produced at the apical bud (shoot tip) is transported basipetally (downward) via polar auxin transport (PAT) through the PINFORMED (PIN) auxin efflux carrier proteins. High IAA concentrations in the main shoot suppress lateral (axillary) bud outgrowth — this is apical dominance. Mechanism: Auxin downregulates cytokinin biosynthesis in axillary buds and maintains high strigolactone levels — both signals inhibit axillary bud activation via BRC1 transcription factor. When the apical bud is removed (pruning), auxin levels drop, cytokinin (produced in roots) dominates, BRC1 is repressed, and dormant axillary buds grow out as lateral branches — creating a bushy, dense plant.

Source: https://mypyqbuddy.com/questions/two-proteins-of-molecular-weights-1-0-times-6a05a8a02adafec47029324d