A fertility clinic records the stages of one IVF procedure in Fig. 1. The woman is given hormones so that several eggs mature. Mature eggs are collected and...
Question 1 Report
A fertility clinic records the stages of one IVF procedure in Fig. 1. The woman is given hormones so that several eggs mature. Mature eggs are collected and mixed with sperm cells in a laboratory dish. The dish is kept at body temperature. Two days later, scientists choose one healthy early embryo and place it in the woman’s uterus. The clinic explains that the remaining embryos may be frozen, with consent, for a later attempt. This treatment can help when a couple cannot achieve fertilisation inside the female reproductive system.
(a) Describe the sequence of events between collecting the eggs and placing an embryo in the uterus. [3]
(b) Explain why the eggs, sperm cells and early embryos are kept close to 37 degrees C. [4]
(c) Suggest three reasons why a clinic may transfer only one embryo during this treatment. [3]
(d) Explain one advantage and two concerns of freezing unused embryos. [3]
Answer Details
(a) Eggs are mixed with sperm cells in a laboratory dish. A sperm fertilises an egg, and the fertilised egg then divides by mitosis to form an early embryo before it is transferred to the uterus. [3]
(b) \(37\,^{\circ}\text{C}\) is close to normal human body temperature. Enzymes work efficiently at or close to their optimum temperature, allowing respiration, metabolism and cell division to occur at suitable rates. At much higher temperatures enzymes can denature; at lower temperatures reactions are slowed. [4]
(c) Transferring one embryo reduces the chance of a multiple pregnancy. This reduces risks to the mother during pregnancy or birth and lowers the risk of premature or low-mass babies. It also reduces pressure on hospital care. [3]
(d) Freezing unused embryos means they may be used in a later attempt without another egg-collection procedure. Concerns include decisions about how long embryos are stored or what happens to them if unused, and ethical or religious objections or possible consent and identity disputes. [3]
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