# DBT JRF 2020 — Question 45

Exam: DBT JRF 2020 · Section: B · Topic: Bioinformatics · Difficulty: Medium

## Question

BLOSUM matrix is used for

## Options

- **A.** homology modelling
- **B.** surface electrostatics
- **C.** DNA homology
- **D.** alignment of protein sequences

## Answer

Option D

## Explanation

Virus-free plant propagation exploits the fact that apical meristematic cells at the shoot apex divide rapidly and typically remain free from systemic viral infection because: (1) Viruses spread through the vascular system (phloem), which is not yet established in newly dividing meristematic cells; (2) The apical dome (the distal 0.1–0.5 mm, containing the true meristem) lacks vascular connections; (3) Cell division rate may outpace viral spread. Very small meristem tips (0.1–0.3 mm, with only 1–2 leaf primordia) excised under sterile conditions and cultured on appropriate media produce virus-free plants. Combined with thermotherapy (37°C treatment) or chemotherapy (antiviral ribavirin), success rates are further improved.

Source: https://mypyqbuddy.com/questions/blosum-matrix-is-used-for-6a05a8a02adafec470293245