Outline the levels of each of the hormones that control the menstrual cycle immediately before
ovulation. [3 marks]
− FSH is released to trigger the development of an immature follicle
− the follicle produces oestrogen, uterine walls thicken as a result
− peaking oestrogen levels at day 12 increase levels of LH
− ovulation occurs at day 14, at the peak of LH levels
Outline the process of in-vitro fertilisation (IVF). [6 marks]
− IVF can only be done on selected candidates of a specific weight, age ranges, and other
criteria (eg. infertility)
− natural menstrual cycle is stopped by regulating LH and FSH
− superovulation is the process of overstimulating the reproductive system, so that multiple
eggs mature at the same time
− eggs are harvested
− sperm are then mixed with the eggs, and this can be done using ICSI, where a single sperm is
directly injected into the egg
− if fertilisation is successful, embryos will develop
− embryos can then be implanted into the uterus
Discuss the ethical issues surrounding IVF. [6]
− IVF can be beneficial because this allows infertile couples to have children, in some
countries, it could also benefit others, such as same-sex couples
− embryos can be screened for genetic disorders before being implanted
− successful embryos that are not implanted can be used for stem cell research, beneficial for
scientific research, as embryos are otherwise difficult to access
− limited access to IVF raises questions regarding medical justice (access to all, based on
clinical need, not ability to pay)
− success rate is quite low
− by choosing which embryos are implanted, we are essentially given the power to choose
who lives and who doesn’t
Fertilisation [8 marks]
− Sperm is attracted to egg by chemotaxis produced by the secondary oocyte
− The sperm passes through the follicle cells and binds to the zona pellucida
− The acrosome reaction occurs when protease is released from the acrosome and digests a
pathway through the zona pellucida
− Cortical reaction is the membrane fusion of the sperm and oocyte, cortical granules release
their contents
− The acrosome and cortical reactions prevent polyspermy
− The enzymes harden the zona pellucida
− Sperm nucleus enters cell, completing the second meiotic division
− Sperm and ovum fuse to form zygote
Pregnancy [8 marks]
− after fertilisation the zygote undergoes repeated mitosis
− after 4-5 days a blastocyst is formed
ovulation. [3 marks]
− FSH is released to trigger the development of an immature follicle
− the follicle produces oestrogen, uterine walls thicken as a result
− peaking oestrogen levels at day 12 increase levels of LH
− ovulation occurs at day 14, at the peak of LH levels
Outline the process of in-vitro fertilisation (IVF). [6 marks]
− IVF can only be done on selected candidates of a specific weight, age ranges, and other
criteria (eg. infertility)
− natural menstrual cycle is stopped by regulating LH and FSH
− superovulation is the process of overstimulating the reproductive system, so that multiple
eggs mature at the same time
− eggs are harvested
− sperm are then mixed with the eggs, and this can be done using ICSI, where a single sperm is
directly injected into the egg
− if fertilisation is successful, embryos will develop
− embryos can then be implanted into the uterus
Discuss the ethical issues surrounding IVF. [6]
− IVF can be beneficial because this allows infertile couples to have children, in some
countries, it could also benefit others, such as same-sex couples
− embryos can be screened for genetic disorders before being implanted
− successful embryos that are not implanted can be used for stem cell research, beneficial for
scientific research, as embryos are otherwise difficult to access
− limited access to IVF raises questions regarding medical justice (access to all, based on
clinical need, not ability to pay)
− success rate is quite low
− by choosing which embryos are implanted, we are essentially given the power to choose
who lives and who doesn’t
Fertilisation [8 marks]
− Sperm is attracted to egg by chemotaxis produced by the secondary oocyte
− The sperm passes through the follicle cells and binds to the zona pellucida
− The acrosome reaction occurs when protease is released from the acrosome and digests a
pathway through the zona pellucida
− Cortical reaction is the membrane fusion of the sperm and oocyte, cortical granules release
their contents
− The acrosome and cortical reactions prevent polyspermy
− The enzymes harden the zona pellucida
− Sperm nucleus enters cell, completing the second meiotic division
− Sperm and ovum fuse to form zygote
Pregnancy [8 marks]
− after fertilisation the zygote undergoes repeated mitosis
− after 4-5 days a blastocyst is formed
