Cystic fibrosis is caused by a recessive lethal gene and can be detected by an excess concentration of chloride in sweat. A normal man whose sister has cystic fibrosis, his normal wife whose brother has cystic fibrosis. What is chance of cystic fibrosis in their child?

#Question id: 10708

#Unit 10. Ecological Principles

Which of the following statements is a likely explanation for why invasive species take over communities into which they have been introduced?

#Question id: 4599

#Unit 11. Evolution and Behavior

Many crustaceans (for example, lobsters, shrimp, and crayfish) use their tails to swim, but crabs have reduced tails that curl under their shells and are not used in swimming. This is an example of ________.

#Question id: 24158

#General Aptitude

#Question id: 5029

#Unit 11. Evolution and Behavior

Which of the following was the least likely factor causing the Cambrian explosion?

#Question id: 7280

#Unit 5. Developmental Biology

In drosophila, Physical forces drive invagination of the ventral furrow. Following statements regarding to this process:

A. The cellularized blastoderm will begin to activate higher levels of myosin in the cells at the ventral midline and preferentially at their apical surface.

B. Epithelial adhesions paired with differential activation of dynein and tissue geometry create mechanical constraints that affect the orientation of actomyosin meshworks.

C. The A/P oriented arrays of myosin in the cells at the ventral midline generate tension along the anterior-posterior axis.

D. The combination of tissue geometry and tension of these anterior-to-posterior meshworks cause the tissue to fold outward at a right angle to the anterior-posterior axis, creating a long and narrow ventral furrow.

Which of the following statements are incorrect?