Arkansas Tech University
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This 3 page Class Notes was uploaded by Surani Notetaker on Tuesday February 16, 2016. The Class Notes belongs to BIOL 1014 at Arkansas Tech University taught by Dr. Jacqueline Bowan in Spring 2016. Since its upload, it has received 19 views. For similar materials see Introduction to Biological Sciences in Biology at Arkansas Tech University.
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Date Created: 02/16/16
Reproduction Reproduction is at the core of who we are as individuals. 1 Case Study: The Fastest Woman on Earth Caster Semenya o People doubted she was a woman after winning race after race. She was subjected to two rounds of DNA tests. o She has no ovaries or uterus. She had undescended testes and testosterone levels 3 times higher than an average woman. Disorder of sexual development: the genitalia are atypical with respect to the number of chromosomes generally associated with the male or female sex. o Males : XY (make sperm either X or Y) o Females: XX (make eggs that have an X) Chromosomes are responsible for primary sex determination. o Whether ovaries or testes form. Secondary sex determination: governs the development of other sex- related characteristics. o Hormones are responsible for these secondary instructions. Chromosome Instructions 1. The embryo has bipotential for sex. 2. The structures that will become sex organs await instructions. 3. One type of instructions is the SRY gene (on Y chromosome) that is responsible for development of the testes. 4. The other type is on the X chromosomes. The DAX1 gene is necessary on both X chromosomes to initiate development of the ovaries. Hormone Instructions 1. In XY, two hormones are released: Anti- Mϋllerian hormone (destroys Mϋllerian ducts) Testosterone (triggers further development of Wolffian ducts) 2. In XX, ovaries secrete estrogen: Promotes development of the Mϋllerian ducts, oviducts, uterus, and upper end of the vagina. 2 What Happens If the Hormonal Signals Are Missing or Misread? Androgen-insensitive syndrome (AIS) in women Aseudohermaphroditism in men Disorder s AIS – individuals are XY but do not develop male parts AIS embryos are exposed to estrogen from the mother and their internal testes. In pseudohermaphroditism, an XY individual develops testes but lacks an enzyme that enables testosterone to send the right signals. External genitals appear female, but the Mϋllerian ducts degenerate and no female ducts form. 3 How Do Men Produce Sperm? Sperm production has to occur at temperatures lower than body temperature, which is why the testes are located outside the body. Testes are divided into wedges, with each wedge containing seminiferous tubules lined with stem cells. After meiosis is complete, the sperm mature in the epididymis. Prostate gland: secretes a fluid that neutralizes the acidity of the vagina. Seminal vesicles: secrete fructose (energy for sperm) and prostaglandins, a signal that causes muscle contraction in the female reproductive tract. 4 How Do Women Produce Eggs? The production of eggs is called oogenesis and starts with an immature egg called a primary oocyte. Once puberty starts, one oocyte completes meiosis I each month. One of the cells, the secondary oocyte, retains most of the cytoplasm. Secondary oocyte starts meiosis II but stops and then bursts from the ovary, which is called ovulation. 5 What Causes Infertility, and How Can It Be Treated? Infertility is the failure to conceive and become pregnant after a year of regular, unprotected intercourse. o One common cause of male infertility is low sperm count. o Pelvic inflammatory disease (PIC) – infertility is caused by blocked oviducts Assisted Reproductive Technology (ART) – reproductive procedures used to bring sperm and eggs together so that fertilization is possible. o Artificial insemination - sperm from the male partner are placed in the female partner’s vagina. o Intrauterine insemination - sperm are placed directly in the uterus. o Gamete intrafallopian transfer (GIFT) - the zygote can be placed in the oviduct instead. o Intracytoplasmic sperm injection (ICSI) - sperm is injected into the egg. The embryo is then placed in the uterus. And when these treatments don’t work….. o Surrogacy - an embryo is placed in the uterus of a woman who is not the biological mother in order to establish a healthy pregnancy. 6 How Can We Tell If a Fetus or Baby Is Healthy? Screens and Diagnostic Tests Amniocentesis Chorionic villus sampling (CVS)
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