Abnormal Motor Proteins Cause Kartagener Syndrome An abnormal form of a motor protein called dynein causes Kartagener syndrome, a genetic disorder characterized by chronic sinus and lung infections. Biofilms form in the thick mucus that collects in the airways, and the resulting bacterial activities and inflammation damage tissues.
Affected men can produce sperm but are infertile. Some have become fathers after a doctor injects their sperm cells directly into eggs. Review FIGURE 4.21 and FIQURE 4.24, then explain how abnormal dynein could cause the observed effects.
FIGURE 4.24 Cross-section of the flagellum of a sperm cell from A a human male affected by Kartagener syndrome and B an unaffected male.
To explain: How abnormal dynein could cause Kartagener syndrome and male infertility.
Introduction: Kartagener syndrome is an autosomal recessive genetic condition characterized by ciliary motility disorder. Cilia are hair-like structures lining the mucus membranes of nose, lungs, and sinuses. In Kartagener syndrome, the cilia do not move properly and defects are found in dynein (a component of cilia) arms. This results in the abnormal morphology of sperm tails and bronchial cilia.
Explanation of Solution
Refer to Fig. 4.20, “How eukaryotic flagella and cilia move” in the textbook. Flagella and ciliary movements are provided by motor protein dynein attached to the nine microtubules arranged in a circle. Abnormality in dynein arms causes Kartagener syndrome. Refer to Fig. 4.24, “Cross-section of a sperm cell from A. a human male affected by Kartagener syndrome and B. an unaffected male” in the textbook. The lack of dynein arms results in the abnormal morphology of sperm tails and bronchial cilia causing lung infections, chronic sinus, and infertility. Men with Kartagener syndrome are infertile but they produce sperms. They are infertile because defected dynein would affect the movement of flagella and cilia. As a result, there would be abnormal sperm motility and it would not be able to swim normally for fertilization.
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Chapter 4 Solutions
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