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10 Cards in this Set
- Front
- Back
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Cytoplasmic Determinant
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Early embryonic cells become different because of the uneven distribution within the unfertilized egg of maternal substances.
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cell differentiation
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specialization of cells in their structure and function. communication of instructions, tells cell what and when to do something.
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Morphogenesis
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an animal takes shape and the differentiated cells end up in the appropriate locations.
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Fertilization
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Sperm penetrates the plasma membrane of the secondary oocyte.
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Steps of fertilization:
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Recognition, Penetration, formation of the fertilization membrane, completion of meiosis II in the secondary oocyte, fusion of nuclei and replication of DNA.
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Recognition:
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the sperm secretes a protein that binds with special receptor molecules that reside on a glycoprotein layer surrounding the plasma membrane of the oocyte. (vitelline layer/zona pellucida) insures that fertilization occurs only between egg and sperm of the same species.
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penetration
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the plasma mebranes of the sperm and oocyte fuse, and the sperm nucleus enters the oocyte.
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formation of the fertilization membrane
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the vitelline layer forms a fertilization membrane which blocs the entrance of additional sperm.
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completion of meisosi II in the secondary oocyte
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sperm penetration triggers meiosis II in the oocyte, producing ovum a dpolar body. the polar body is discharged trhoug the plasma membrane.
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fusion of nuclei and replication of dna
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the sperm and ovum nuclei fuse, forming a zygote nucleus consting of 23 pairs of chormosomes(inhumans) each chromosome replicates so that it consists of two identical chromatids
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