Factors affecting the possibility of clinical effects of chromosome aberrations

Correct Answer: D

Rationale: The correct answer is D because all factors listed (A, B, and C) can influence the clinical effects of chromosome aberrations. A) Whether genetic material is lost or gained affects the function of genes. B) The amount of genetic material lost or gained can lead to more severe consequences. C) Euchromatic vs. heterochromatic material influences gene expression and function. Therefore, considering all these factors together provides a comprehensive understanding of the clinical effects of chromosome aberrations. Other choices are incorrect because they only focus on individual aspects and do not provide a holistic view.

Correct Answer: A

Rationale: Step 1: Unique DNA sequences are low copy number regions that are present in the genome in limited copies. Step 2: These sequences anneal slowly because of their low copy number, making them distinct from high copy number sequences. Step 3: Unique sequences can include functional genes as well as non-coding regions. Step 4: By combining steps 1-3, we can conclude that all of the above statements are true for unique DNA sequences, making option A correct. Summary: Option B is incorrect because the slow annealing is specific to unique sequences. Option C is incorrect as unique sequences can include non-functional regions too. Option D is incorrect because unique sequences can represent more than 1.5% of the human genome.

Correct Answer: D

Rationale: The correct answer is D (All of the above). Fetal cells in maternal blood include lymphocytes, nucleated erythroblasts, and extra villus cytotrophoblasts. Lymphocytes can cross the placental barrier, nucleated erythroblasts are fetal blood cells, and extra villus cytotrophoblasts are from the placenta. These fetal cells can be detected in maternal blood samples through various methods, making D the correct choice. Choices A, B, and C are incorrect as they only represent specific types of fetal cells found in maternal blood, while D encompasses all potential types.

Correct Answer: A

Rationale: The correct answer is A because preimplantation diagnosis involves screening embryos for genetic abnormalities before they are transferred to the uterus, allowing for the exclusion of abnormal embryos. This ensures that only healthy embryos are selected for implantation, increasing the chances of a successful pregnancy. Choice B is incorrect because preimplantation diagnosis is not done for the creation of stem cells but rather to identify genetic abnormalities. Choice C is incorrect because the purpose of preimplantation diagnosis is not to make decisions about terminating pregnancies but to select healthy embryos for transfer. Choice D is incorrect because preimplantation diagnosis must be done before implantation to identify abnormal embryos and avoid transferring them.

Correct Answer: A

Rationale: Step-by-step rationale: 1. In vitro fertilization (IVF) is commonly used when a couple faces infertility issues. 2. IVF involves fertilizing an egg with sperm outside the body in a laboratory setting. 3. This method helps couples who struggle with conceiving naturally. 4. Choice A is correct as it aligns with the primary purpose of IVF for couples experiencing fertility problems. Summary: - Choice B is incorrect as preimplantation diagnosis is a separate procedure within IVF. - Choice C is incorrect as IVF is not primarily for observing early development but for assisting in conception. - Choice D is incorrect as the optimization of the fertilized egg is not the main goal of IVF, but rather achieving pregnancy for couples with fertility challenges.