After crystal violet staining, the Gram-positive bacteria may appear dark blue or violet. The cell wall of gram positive bacteria have thick peptidoglycan layer, thus it retains the crystal violet stain compared to gram negative bacteria.
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Answer:
True
Explanation:
Chiasma is the site of crossing over. It is an X-shaped site that appears in a tetrad (bivalent) chromosome during the diplotene stage of prophase I of meiosis I. Crossing over refers to the exchange of segments of chromatids and occurs between homologous chromosomes only. Crossing over is the event of prophase I of meiosis I and produce new gene combinations. 
The homologous chromosomes are separated from each other but remain attached at chiasmata. The dissolution of chiasmata occurs by the end of prophase I and separates the homologous chromosomes completely from each other. Crossing over does not occur in mitosis. Since mitosis does not include crossing over, chiasmata are also not formed in mitosis. 
 
        
             
        
        
        
Answer:
<em>The overuse of pesticides</em>
Explanation:
Pesticides are usually sprayed on plants so that the pest organisms can be killed. But these chemicals sprayed on plants can be toxic for humans when humans consume crops which have been sprayed with pesticides. Also, erosion causes these toxic chemicals to get eroded in the nearby lakes. The chemicals in the pesticides are harmful for every life that uses this water. Hence, the overuse of pesticides might kill pests but it is also toxic for consumption by humans. 
 
        
             
        
        
        
ATMOSPHERE LAYERS: Troposphere, Stratosphere, Mesosphere and Thermosphere 
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