Briefly state the key events of gamete formation, fertilization, cleavage, and organ formation.?

Question

need help please!

Answer 1

1) Gamete Formation: A germ cell, either sperm or egg, undergoes meiosis. This causes the single germ cell to go from a diploid cell to 4 haploid daughter cells. Because of the chromosomal crossover that occurs in Prophase I of Meiosis I, this allows the 4 daughter cells to be genetically unique.

2) Fertilization: Once formed, the sperm and egg cell meet in the uterus of the fertile female. The sperm releases an enzyme to break part of the egg's membrane, before attaching. Genetic information is dumped from the sperm to the egg cell, creating a diploid zygote.

3) Cleavage: Once formed, the zygote begins to divide rapidly, undergoing mitosis to form the embryo. These divisions occur (look up on embryoes on Wikipedia--believe it or not, they go into pretty good detail) rapidly. There zygote goes from a single cell to 2 cells, then 4,then 8, then 16, then 32, then to a blastula (which is a ball of cells), a gastrula (a hollow ball of cells that eventually folds on itself) and slowly becomes the embryo.

4) Organ formation: I'm not sure I understand what you're asking, since this can mean a lot. But in the embryo, what happens is that there comes a stage, around the formation of the blastula, where cell specialization occurs. That means that all the cells, which were once identical, begin to shuffle organelles across each other's membranes, giving say, the muscle cells more mitochondria or the bone cells more cytoskeleton. This makes certain cells "designed" for a certain job, of which the stems cells produce. This is why stem cell research is so crucial--these cells can become any cell. When these specialized cells begin to work together, say, they connect, they become a tissue. When a group of tissues work together, they become an organ. Mind you, this is a HUGE generalization--but I assume that's what you wanted?

Hope this helps.