Question

IUILIUL Urug in the gradient. On occasion, the gradient plate technique will not display colonies of m because there were none in the original culture. Questions 1. Discuss several methods by which mutations can be induced in bacteria. 2. How might antibiotic-resistant bacteria have arisen by spontaneous muta- tion in the natural environment? 3. Suppose an organism were unable to synthesize an essential nutrient for its growth. How could the gradient plate technique be used to detect a mutant organism that was able to synthesize the nutrient? 4. What method might be used to determine whether an induced mutation was a temporary or permanent change in the organism? 5. List some environmental chemicals that may induce mutations in bacter- ial species.

Answer 1

• Mutation is a permanent alteration in the sequence of nitrogenous bases. of a DNA molecule. Types of mutation & - utations are classified on the basis of kinds of alterations in the DNA or by I whether the mutation was Spontaneous or induced by a mutagen in the environment. Mechanisms / Methods by which mutations be induced in bacteria ? Radiation - X-rays, other types of radiation treatments that are used include gamma rays and fast neutron bomband ment. These induce point mutation I change in single trucleotide) or deletions (loss of a chromosomal segment). Chemical - Two types of chemical mutagens used are Takylating agents and I base analogs Alculating agent (eg: mustard gas) can mutate replicating as well and non- replicating DNAS (2)

(3) A base analog / Ege S-bromo uracil) can only mutalt. DNA when an analog is incorporated into the replicating ONA. Transposon insertion - Transposable etements are mobile preces of DNA . They can move from one a location in a genome to Janother. When they relocate to a new location, they cause mutation.