Anonymous
Anonymous asked in Science & MathematicsBiology · 1 decade ago

Which of the following processes occurs when a salamander regenerates a lost limb?

A. Oncogenes that cause accelerated cell division are turned on.

B. Certain cells in the limb dedifferentiate, divide, and then redifferentiate to form a new limb.

C. A new salamander develops from the lost limb.

D. The homeotic genes of the regenerating cells turn off.

E. The cell cycle is arrested and apoptosis begins.

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  • Anonymous
    1 decade ago
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    The answer is:

    B. Certain cells in the limb dedifferentiate, divide, and then redifferentiate to form a new limb.

    Reason: In salamanders, the regeneration process begins immediately after amputation. Limb regeneration in the axolotl and newt have been extensively studied. After amputation, the epidermis migrates to cover the stump in less than 12 hours, forming a structure called the apical epidermal cap (AEC). Over the next several days there are changes in the underlying stump tissues that result in the formation of a blastema (a mass of dedifferentiated proliferating cells). As the blastema forms, pattern formation genes – such as HoxA and HoxD – are activated as they were when the limb was formed in the embryo. The distal tip of the limb (the autopod, which is the hand or foot) is formed first in the blastema. The intermediate portions of the pattern are filled in during growth of the blastema by the process of intercalation. Motor neurons, muscle, and blood vessels grow with the regenerated limb, and reestablish the connections that were present prior to amputation. The time that this entire process takes varies according to the age of the animal, ranging from about a month to around three months in the adult and then the limb becomes fully functional.

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