Question

1.How does female hormonal birth control work? If you were to develop a male hormonal birth control, what pathway would you target and why?

2.What happens when more than one sperm fertilizes an egg? Do you get a “viable” pregnancy?   Why or why not

Answer 1

1.Birth control pills are medication used to prevent pregnancy. They contain hormones that suppress ovulation. The most effective type is the combination pill which contains both oestrogen and progestin, a synthetic form of progesterone. These two hormones interfere with the normal menstrual cycle to prevent ovulation. The menstrual cycle refers to the monthly events that occur within a woman's body in preparation for the possibility of pregnancy. Each month one egg is released from the ovary called ovulation. At the same time the lining of the uterus thickens ready for pregnancy. Iffertilization does not take place the lining of the uterus is shed in menstrual bleeding and the cycle starts over.The menstrual cycle is underthe control of multiple hormones secreted by the hypothalamus pituitary gland and ovaries. Basically the hypothalamus produces gonadotropin-releasing hormone GnRH. The pituitary secretes follicle ovary stimulating hormone FSH and luteinizing hormone LH while the ovaries produce oestrogen and progesterone.These hormones are involved in a regulatory network that results in monthly cyclic changes responsible for ovulation and preparation for pregnancy.The two hormones that are required for ovulation are FSH which starts the cycle by stimulating immature follicles to grow and produce a mature egg and LH which is responsible for the release of the egg from the ovary the ovulation event itself. To other hormones oestrogen and progesterone are at high levels after ovulation in the second half of the cycle. They suppress FSH and LH during this time preventing the ovaries from releasing more eggs.If fertilization occurs oestrogen and progesterone levels remain high throughout pregnancy providing a continuous suppression of ovulation.On the other handin the absence of pregnancy their levels fall causing menstrual bleeding.The levels of oestrogen and progesterone in the combination pills mimic the hormonal state after ovulation,leading the ovaries into thinking that ovulation has already occurred. FSH and LH are constantly suppressed. No egg is matured or released.The pills are taken everyday for 3 weeks followed by 1 week of Placebo pills containing no hormones.During the week of Placebos oestrogen and progesterone levels fall triggering so called withdrawal bleeding or fake periods.The bleeding serve as a convenient indication that fertilization did not happen but it is not required for birth control. In fact the exist continuous use contraceptive pills with less or no placebos resulting in less or no menstrual periods. These pills are particularly beneficial for women who suffer from menstrual disorders such as excessive menstrual bleeding, painful menstruation and endometriosis.For lactating women for those who cannot tolerate oestrogen, there are many pills that contain only progestin. These are not as effective as combination pills in preventing ovulation.Their effect relies more on the ability of progestin to promote secretion of a thick cervical mucus to obstruct sperm entry.

If a male contraceptive pill is to be developed, its action can be suppression of the endogenous hormone FSH and the own production of testosterone in low level so that this will affect the the development of sperm. Because the pituitary gland releases follicle stimulating hormone (FSH) and luteinizing hormone (LH) into the male system. FSH enters the testes, stimulating the Sertoli cells, which help to nourish the sperm cells that the testes produce, to begin facilitating spermatogenesis.LH stimulates the testes to release testosterone.Testosterone works with follicle stimulating hormone (FSH) to aid in spermatogenesis.The male contraceptive pill may contain hormones which are designed to stop sperm production. Should be temporary blockage of production of sperms.

2.In normal case, Fertilization membrane surrounds the egg, suggeting it has been fertilized. Membrane prevents other sperm from entering. A new membrane forms around the genetic material creating a male pronucleus.Inside genetic material reforms into 23 chromosomes. The female genetic material awakened by the fusion of the sperm with the egg finishes dividing resulting in the female pronucleus which also contains 23 chromosomes.As the male and female pronuclei form spider web like threads called microtubules pull them towards each other,the two sets of chromosomes join together completing the process of fertilization. At this moment a unique genetic code arises instant determining gender hair colour eye colour and hundreds of other characteristics.

However multiple sperm cells entered the egg prior to fertilization membrane, which is called polyspermy.This means that zygote will not be able to successfully make first cell division and will mutate and die.Because of multiple sperm cells pronuclei unable to properly centrate and thus start first cell division.The zygote begins to display abnormal cleavage.Although zygote appears to have made cell division, its multiple chromosomes from multiple sperm cells and only one egg cannot divide properly and equally. Hence there is no probability of a viable pregnancy.