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kvasek [131]
3 years ago
8

12.

Biology
1 answer:
r-ruslan [8.4K]3 years ago
8 0

Answer:

d

Explanation:

The tetrad is formed by synapsis of homologous chromosomes.

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11 chromosomes

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The relationship between a host and a pathogen is dynamic, since each modifies the activities and functions of the other. The outcome of such a relationship depends on the virulence of the pathogen and the relative degree of resistance or susceptibility of the host, due mainly to the effectiveness of the host defense mechanisms. Staphylococcus aureus, arguably the most prevalent pathogen of humans, may cause up to one third of all bacterial diseases ranging from boils and pimples to food poisoning, to septicemia and toxic shock. Electron micrograph from Visuals Unlimited, with permission.

The Underlying Mechanisms of Bacterial Pathogenicity

Two broad qualities of pathogenic bacteria underlie the means by which they cause disease:
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2. Toxigenesis is the ability to produce toxins. Bacteria may produce two types of toxins called exotoxins and endotoxins. Exotoxins are released from bacterial cells and may act at tissue sites removed from the site of bacterial growth. Endotoxins are cell-associated substance. (In a classic sense, the term endotoxin refers to the lipopolysaccharide component of the outer membrane of Gram-negative bacteria). However, endotoxins may be released from growing bacterial cells and cells that are lysed as a result of effective host defense (e.g. lysozyme) or the activities of certain antibiotics (e.g. penicillins and cephalosporins). Hence, bacterial toxins, both soluble and cell-associated, may be transported by blood and lymph and cause cytotoxic effects at tissue sites remote from the original point of invasion or growth. Some bacterial toxins may also act at the site of colonization and play a role in invasion. Acid-fast stain of Mycobacterium tuberculosis, the agent of tuberculosis (TB). The bacteria are the small pink-staining rods. More than one-third of the world population is infected. The organism has caused more human deaths than any other bacterium in the history of mankind. Although its ability to produce disease is multifactorial, it is not completely understood. American Society of Microbiology, with permission.
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<span>When the student added X, Y and Z to the test tubes. The one which is a catalyst fastened the reaction.</span>

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