The mtDNAs of most multicellular animals are approximately 16-kb circular molecules that encode intron-less genes compactly arranged on both DNA strands.

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#Id: 7894

#XL - Q Biochemistry

The mtDNAs of most multicellular animals are approximately 16-kb circular molecules that encode intron-less genes compactly arranged on both DNA strands.

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#Id: 9938

#XL - T Zoology

Host immune responses and bacterial evasion mechanisms

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#Id: 9939

#XL - T Zoology

Tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis.

Pulmonary infection usually results from inhalation of small droplets of respiratory secretions containing a few bacilli.

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#Id: 9940

#XL - T Zoology

The inhaled bacilli are ingested by alveolar macrophages in the lung and inhibiting formation of phagolysosomes

CD4+ T cells are activated within 2 to 6 weeks after infection.

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#Id: 9941

#XL - T Zoology

These cells wall off the organism inside a granuloma called a tubercle. The localized concentrations of lysosomal enzymes in these granulomas can cause extensive tissue necrosis.

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#Id: 9942

#XL - T Zoology

Diphtheria

Natural infection with C. diphtheriae occurs only in humans and is spread by respiratory droplets. 

The organism colonizes the nasopharyngeal tract and causes little tissue damage, with only a mild inflammatory reaction. 

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#Id: 9943

#XL - T Zoology

Virulence is due to its potent exotoxin, which destroys the underlying tissue and results in heart, liver, and kidney damage, as well as to suffocation following formation of a tough fibrous membrane in the respiratory tract