Small chromosome deletions can cause “contiguous gene syndromes” because

Correct Answer: C

Rationale: The correct answer is C because small chromosome deletions involving a number of linked genes can lead to contiguous gene syndromes due to the deletion affecting multiple genes in close proximity. This can result in a cluster of related symptoms or phenotypes. Choices A and B are incorrect because the presence or absence of centromere or telomere in the deletion does not directly lead to contiguous gene syndromes. Choice D is incorrect as the deletion affecting genes at the breakpoints may not necessarily cause contiguous gene syndromes unless multiple genes in close proximity are involved.

Correct Answer: B

Rationale: The correct answer is B because FISH (Fluorescence In Situ Hybridization) uses specific DNA probes that target a particular chromosome or chromosomal region. This allows for the visualization and analysis of specific genetic information without the need for spreads of mitotic chromosomes. Choice A is incorrect because FISH does not necessarily use DNA from whole chromosomes. Choice C is incorrect as chromosomes play a crucial role in genetic information. Choice D is incorrect because while chromosomes contain both DNA and protein, this is not the reason why FISH can provide genetic information without spreads of mitotic chromosomes.

Correct Answer: B

Rationale: The correct answer is B because karyotypes are generated by comparing the binding of probes from the experimental sample to a normal sample. This comparison allows for the visualization of chromosomal abnormalities. By analyzing the differences in probe binding patterns between the two samples, one can identify any genetic variations or mutations present. This method helps in identifying structural abnormalities in chromosomes. Choice A is incorrect because the number of probes used does not determine the generation of karyotypes. Choice C is incorrect as maternal DNA signal versus fetal DNA signal is not relevant to generating karyotypes. Choice D is also incorrect because comparing lymphocytes versus fetal nucleated erythroblasts does not directly lead to the generation of karyotypes.

Correct Answer: B

Rationale: Step-by-step rationale for why answer B is correct: 1. Difficulty getting pregnant is typically related to fertility issues, not necessarily genetic problems. 2. Genetic problems manifest in structural abnormalities, aberrant chromosomes, or inherited conditions. 3. Options A, C, and D all involve indicators of genetic issues through birth abnormalities or aberrant chromosomes. 4. Difficulty getting pregnant does not directly point towards a genetic problem but rather reproductive health issues.

Correct Answer: D

Rationale: The correct answer is D: Ultraviolet light. UV radiation has higher energy levels compared to visible light, infrared, and EMF, making it capable of damaging DNA and causing mutations that can lead to cancer. UV exposure is a known risk factor for skin cancer. Visible light and infrared do not have enough energy to cause DNA damage and cancer. EMF (electromagnetic fields) have not been proven to directly cause cancer. In summary, only UV light has the necessary energy to cause cancer, making it the correct choice among the options provided.