Human Develop (Your Body) (Your Body, How It Works)
Ted Zerucha
Language: English
Pages: 112
ISBN: 0791076318
Format: PDF / Kindle (mobi) / ePub
Provides an overview of human development, discussing fertilization, cell development, and cell movement.
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altogether, either with a donor heart or with a mechanical device. In the future, the use of mechanical hearts will probably be common in patients who would otherwise die of heart disease. Until the mid-twentieth century, infections and contagious diseases related to viruses and bacteria were the most common causes of death. Even a simple scratch could become infected and lead to death from “blood poisoning.” After penicillin and other antibiotics became available in the 1930s and 40s, doctors
normal (wild type) Drosophila is shown on the left. A Drosophila displaying the antennapedia mutatation is shown on the right. The antennapedia Drosophila mutant has legs replacing its antennae. flies likely play some role in patterning the anterior-posterior axis of the fly. The genes that are mutated in the Drosophila genome that lead to these homeotic alterations in the bodies of the adult flies are called homeotic genes, or HOM genes. There are actually eight different HOM genes in the
during patterning of the trunk of the body, early patterning of the limb involves broadly establishing the axes (for example the signals released by the ZPA) and then refining these axes. In fact, this chapter has illustrated how many of the mechanisms that are used during development of the trunk of the body can be used again, in a different context, to control additional aspects of development, in this case, the limbs. For example, the Hox genes not only have a role in the specification of
Cell Humans begin as a single cell, or zygote, when the sperm and egg join. The zygote divides to give rise to two cells that are virtually identical to each other. These two daughter cells are then capable of each dividing to give rise to four cells, which can then, in turn, divide again. This process allows for an exponential increase in cell number as each round of cell division can potentially double the number of cells produced by the previous division. This type of mechanism involving
now be examined. A typical animal cell (Figure 3.1) is similar to a container filled with specific structures. It is this collection of structures that act together for the cell to function. The outer surface, or walls, of this container is known as the plasma membrane. The plasma membrane acts to separate the inside of the cell from its surroundings, much like the function of our skin. Contained within the cell are many structures, called organelles, which play important roles in the functions a