# DBT JRF 2020 — Question 27

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

## Question

For a microbial culture, if the doubling time is 0.231 h, the specific growth rate (in $h^{-1}$ ) will be (assume that the endogenous metabolism is negligible)

## Options

- **A.** 2.5
- **B.** 0.3
- **C.** 3.0
- **D.** 1.0

## Answer

Option C

## Explanation

Cybrids (cytoplasmic hybrids) are produced by fusing a cytoplast (an enucleated cell — a cell from which the nucleus has been physically removed by cytochalasin B + centrifugation) with an intact whole cell that retains its nucleus. The resulting cybrid contains: the nuclear genome of the whole cell donor + cytoplasm/organelles (mitochondria, plastids/chloroplasts) from the cytoplast donor. This technique is used to: (1) study organelle genetics and cytoplasmic inheritance; (2) create plants with novel cytoplasmic male sterility (CMS) for hybrid seed production; (3) introduce foreign mitochondria for disease modelling. Cybrids are distinct from somatic hybrids (fusion of two complete cells, combining both nuclear genomes).

Source: https://mypyqbuddy.com/questions/for-a-microbial-culture-if-the-doubling-time-6a05a8a02adafec470293233