Prokaryotes + Viruses

Question 1

Describe bacteria division

Answer 1

1. Cell replicates DNA (plasmids + circular chromatids)
   (cytoplasmic membrane elongates, separating DNA molecules
2. Cross wall forms; membrane invaginates
3. Cross wall formed and 2 daughter cells produced

Question 2

Compare binary fission to mitosis

Answer 2

Both involve 1 cell division to produce 2 daughter cells
Both replicate DNA prior to cell division - grow before dividing
Only mitosis condenses chromosomes
Only mitosis contains cell cycle checkpoints
Only mitosis breaks down nuclear envelope
Only mitosis has spindle fibres

Question 3

How does bacterial population grow?

Answer 3

lag phase - adapting to environment
exponential phase - optimum rate of binary fission
stationary phase - birth = death - limited resources / build up of toxins
death phase - no resources e.g. oxygen / increase concentration of toxins

Question 4

What are the characteristics of viruses?

Answer 4

acellular + non-living
replicate by host cell

Question 5

What are examples of viruses?

Answer 5

HIV, tobacco mosaic virus

Question 6

How do viruses replicate?

Answer 6

Virus attachment protein attaches to cell receptors
Virus injects nucleic acid into host cell
Viral nucleic acid replicated in cell
Viral protein is produced
Viral components assembled and released from cell

Question 7

Why don’t viruses undergo cell division?

Answer 7

acellular

Question 8

What happens following injection of their nucleic acid?

Answer 8

injected host cell replicates the viral particles