An inversion moves a wild-type allele (red eyes) at the white locus in Drosophila to a chromosomal region that contains highly condensed, the wild-type allele is not expressed in some cells, resulting in an eye consisting of red and white spots.

TLS Online TPP Program

#Id: 9942

#Unit 4. Cell Communication and Cell Signaling

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

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#Id: 9944

#Unit 4. Cell Communication and Cell Signaling

Malaria (Parasitic)

Sporozoites enter the bloodstream by mosquito.

The sporozoites migrate to the liver, where they multiply, transforming liver hepatocytes into giant multinucleate schizonts, which release thousands of merozoites into the bloodstream. 

TLS Online TPP Program

#Id: 9945

#Unit 4. Cell Communication and Cell Signaling

The merozoites infect red blood cells, which eventually rupture, releasing more merozoites. 

TLS Online TPP Program

#Id: 9946

#Unit 4. Cell Communication and Cell Signaling

Eventually some of the merozoites differentiate into male and female gametocytes, which are ingested by a mosquito and differentiate into gametes in the mosquito’s gut. 

TLS Online TPP Program

#Id: 9947

#Unit 4. Cell Communication and Cell Signaling

The gametes fuse to form a zygote that differentiates to the sporozoite stage within the salivary gland of the mosquito.