Answer:
Mitosis occurs in somatic cells; this means that it takes place in all types of cells that are not involved in the production of gametes. Prior to each mitotic division, a copy of every chromosome is created; thus, following division, a complete set of chromosomes is found in the nucleus of each new cell. Indeed, apart from random mutations, each successive duplicate cell will have the same genetic composition as its parent, due to the inheritance of the same chromosome set and similar biological environment. This works well for replacing damaged tissue or for growth and expansion from an embryonic state. Because the genes contained in the duplicate chromosomes are transferred to each successive cellular generation, all mitotic progeny are genetically similar. However, there are exceptions. For example, there are genetic variations that arise in clonal species, such as bacteria, due to spontaneous mutations during mitotic division. Furthermore, chromosomes are sometimes replicated multiple times without any accompanying cell division. This occurs in the cells of Drosophila larvae salivary glands, for example, where there is a high metabolic demand. The chromosomes there are called polytene chromosomes, and they are extremely large compared to chromosomes in other Drosophila cells. These chromosomes replicate by undergoing the initial phases of mitosis without any cytokinesis (Figure 2). Therefore, the same cell contains thick arrangements of duplicate chromosomes side by side, which look like strands of very thick rope. Scientists believe that these chromosomes are hyper-replicated to allow for the rapid and copious production of certain proteins that help larval growth and metamorphosis
Explanation:
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<u>Answer</u>: Option b false
<u>Explanation</u>:
- Refrigerating or freezing foods <em>does not kill all or most of the bacteria</em> in the food as lowering the temperatures of the food only renders the microbes present in it <em>inactive</em>. As soon as the food is brought back to normal temperature, the microorganisms present in it become active again.
- The advantage of freezing food is only limited to the fact that once the food is frozen, all the microbes be it fungus, bacteria etc. become inactive and do not multiply and thus, freezing prolongs the shelf life of food, however once this food is thawed the micro organisms again become active and start multiplying and can easily cause food borne illness.
- So, the only way to kill the micro organisms present in the food is to cook the food to correct temperatures and not freezing.