Karyotypes were first performed using blood samples taken from youngsters and adults. Later, a pre- birth process called amniocentesis was developed which allowed medical researchers to obtain samples of cells from extraembryonic fluid located in the amniotic sac, which surrounds an unborn child.
T pollen grain fertilizes an egg cell while a second fuses with two polar nuclei to produce a triploid body that gives rise to the endosperm.
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Answer:
Letter B.
Explanation:
Aquaporins, also known as "water channels," are the main transport of water through the membranes of plant, animal, and bacterial cells. These channels allow the water to travel into and within cells and, at the same time, exclude the passage of ions and solutes.
What makes letter B the correct answer, is the form of transport and shape of the channel that allow water according to the osmotic gradient. In this model, letter A shows simple diffusion, while C and D seem to illustrate gated channels.