A plasmid isa. Lives together with chromosomes b. Shows dependent assortment c. Can replicate independently d. Cannot replicate

Sure, here are the step by step solutions: Step 1: Definition $\begin{array}{rl}\text{Plasmid}& =\text{extra chromosomal circular DNA molecule}\\ & \text{which replicates independently in the host chromosome.}\end{array}$ Step 2: Explanation Plasmids are small, circular DNA molecules that can exist independently of the host chromosome in bacteria and some other organisms. They are not essential for the survival of the host cell, but they can provide various benefits such as antibiotic resistance, virulence factors, and metabolic capabilities. Step 3: Characteristics - Plasmids are usually smaller than the host chromosome. - They can replicate independently of the host chromosome, using their own replication machinery. - They can be transferred between cells through various mechanisms, such as conjugation, transformation, and transduction. - They often carry genes that are not essential for the survival of the host cell, but can provide selective advantages in certain environments. Step 4: Importance The study of plasmids has important applications in various fields, such as biotechnology, medicine, and environmental science. Plasmids can be used as vectors for genetic engineering, allowing researchers to introduce new genes into cells and organisms. They can also be used as tools for studying gene regulation, protein expression, and other biological processes. In medicine, plasmids are being developed as vehicles for gene therapy, which aims to treat genetic disorders by introducing healthy genes into affected cells. In environmental science, plasmids are being studied for their role in antibiotic resistance and the spread of antibiotic-resistant bacteria in the environment.