Question

1. Eukaryote cells require hours for mitosis to occur. Prokaryotes can often divide into two cells in 10-30 minutes. What cell characteristics explain the difference in the length of time required for division? (4 pts)

2. Biology students boiled water for a short period of time, after which the water is checked for the presence of living cells. When it was determined that no active, living cells were present, the water was used to make agar, a media used for bacterial growth. Within 48 hours, numerous colonies of cells began growing on the agar. What type of prokaryote was growing on the agar? Why was the organism not detected in the water? (6 pts)

3. If prokaryotes were unable to convert nitrogen gas into ammonia or nitrate, how would life on Earth be different than it is today? (4 pts)

4. There are two broad categories within kingdom Protista. The ________ are motile and heterotrophic. The ______ are photosynthetic and may or may not be motile. (2 pts)

5. List three characteristics shared between bacteria and archaea. (4 pts)

Answer 1

ANSWER 1 :-

1. Mitosis is the process of cell division which is composed of Karyokinesis and Cytokinesis. It occurs in both Eukaryotes and Prokaryotes although the prokaryotes do not show presence of a well defined nucleus, the genetic material called as the DNA is mainly located in the nucleoid. This in turn undergoes rapid mitotically division to form the daughter cells.
2. In case of the Eukaryotes, the chromosomes and the DNA is localized in the nucleus and thus the process of DNA replication becomes more complicated more probably due to the length of the DNA or the number of chromosomes.
3. Prokaryotes like the bacterial cell have a circular DNA in the form of plasmid which has an 'ori' of replication. This undergoes replication of the template strand in both the directions and is therefore termed as bidirectional replication process. This in turn speeds up replication.
4. In case of Eukaryotes, mitotically spindles act as base for movement and positioning of the chromosomes but in case of the prokaryotes the mechanisms of cytokinesis is totally different and there is no need of formation of spindle fibres.
5. The role of cytokinesis is directly under the control of cytoplasmic protein called as FtsZ gene (Filamenting Temperature sensitive mutant Z) which plays a vital role in the formation of the cleft needed to separate the two cells after Karyokinesis. Due to circular nature of DNA, at the time of replication, there is assembly of the DNA near the middle part of the cell followed by division during which the newly formed structures migrates away from the middle portion to the terminal regions. The FtsZ proteins migrates to the middle zone to form the cleft by means of assembly and leads to division of the cytoplasm irrespective of formation of mitotically spindle to mediate the process.
6. Thus, the time requirement for mitotically division is less in case of Prokaryotes than in the Eukaryotes.

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