Botany MCQs
Topic Notes: Botany
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
Which morphological form of Streptococcus pneumoniae is characterized as non-virulent and mutant?
Answer:
rough form
The rough (R) form of Streptococcus pneumoniae lacks the polysaccharide capsule required for virulence. Because it cannot evade the host immune system, it is considered non-virulent. This phenotype is often associated with mutations that prevent the synthesis of the protective capsule.
2
What is the term for the genetic recombination process where a bacterium actively takes up naked DNA from its environment?
Answer:
transformation
Transformation is a mechanism of horizontal gene transfer in bacteria where a competent cell takes up free, naked DNA fragments from the surrounding medium. Once inside, the DNA may be integrated into the bacterial chromosome, potentially altering the genetic makeup of the recipient cell.
3
Which morphological form of Streptococcus pneumoniae is identified as the normal, virulent, and pathogenic strain?
Answer:
smooth form
The smooth (S) form of Streptococcus pneumoniae possesses a thick polysaccharide capsule. This capsule protects the bacteria from phagocytosis by the host's immune system, making the strain virulent and capable of causing disease in the host.
4
What are the primary types of competence observed in bacterial cells regarding DNA uptake?
Answer:
a and b both
Competence refers to the physiological state of a bacterium that allows it to take up exogenous DNA. Natural competence occurs under specific environmental conditions, while artificial competence is induced in the laboratory through chemical treatments or physical methods like electroporation.
5
How many distinct forms of transduction are recognized in bacterial genetics?
Answer:
three
There are three primary recognized forms of transduction in bacteria: generalized transduction, specialized transduction, and abortive transduction. These processes involve the transfer of genetic material from one bacterium to another via a bacteriophage vector, playing a significant role in horizontal gene transfer and bacterial evolution.
6
Which scientist provided the initial experimental evidence suggesting that DNA acts as the hereditary material?
Answer:
frederick griffith
Frederick Griffith conducted the famous transformation experiment in 1928 using Streptococcus pneumoniae. By observing that non-virulent bacteria could be transformed into virulent strains by heat-killed virulent bacteria, he provided the first evidence of a 'transforming principle,' which was later identified as DNA.
7
Which of the following are recognized morphological forms of the bacterium Streptococcus pneumoniae?
Answer:
a and b both
Streptococcus pneumoniae exists in two primary forms: the smooth (S) form, which is encapsulated and virulent, and the rough (R) form, which lacks a capsule and is non-virulent. These distinct colony morphologies are fundamental to understanding bacterial pathogenesis and transformation experiments.