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Reproductive Technologies Can Enhance Fertility

Reproductive Technologies Can Enhance Fertility - •...

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Reproductive Technologies Can Enhance Fertility About 1 in 6 couples is infertile due to physical or physiological conditions preventing gamete production, implantation, or fertilization. Blocked oviducts (often from untreated STDs) are the leading cause of infertility in females. Low sperm count, low motility, or blocked ducts are common causes of male infertility. Hormone therapy can cause increased egg production. Surgery can open blocked ducts. About 40 of the cases are due to male problems, 40 due to female problems and the remaining 20% are caused by some unknown agent(s). In vitro fertilization (test- tube babies) is a widely used technique to aid infertile couples. Fertilization and Cleavage Fertilization has three functions: 1. transmission of genes from both parents to offspring 2. restoration of the diploid number of chromosomes reduced during meiosis 3. initiation of development in offspring Steps in Fertilization
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Unformatted text preview: • Contact between sperm and egg • Entry of sperm into the egg • Fusion of egg and sperm nuclei • Activation of development Cleavage Cleavage is the first step in development of ALL multicelled organisms. Cleavage converts a single-celled zygote into a multicelled embryo by mitosis. Usually, the zygotic cytoplasm is divided among the newly formed cells. Frog embryos divide to produce 37,000 cells in a little over 40 hours. The blastula is produced by mitosis of the zygote, and is a ball of cells surrounding a fluid-filled cavity (the blastocoel ). The decreasing size of cells increases their surface to volume ratio, allowing for more efficient oxygen exchange between cells and their environment. RNA and information carrying molecules are distributed to various parts of the blastula, and this molecular differentiation sets the stage for the layering of the body in the next phases of development....
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