本题目来源于试卷: Unity and Diversity A.2 Nucleic Acids，类别为 IB生物学
[单选题]
The table shows the nucl sr (h4p) l 1byrm-c6;ml/lpwqeotide base sequence and genome size (n -z nu3csoch 7i;74oxdumber of base pairs, bp) for different sp ; cun-ocs7d h z37xoi4ecies.
Which conclusion can be drawn, based on the table?
A. Genome size is proportional to the size of the species.
B. The more closely related two species are, the more similar their base sequences.
C. Humans have more genes than chimpanzees, mice and horses.
D. The base sequence in the table for humans and chimpanzees is the same, therefore they have an identical genetic code.
参考答案: B
本题详细解析:
Species that share a recent common ancestor, such as humans and chimpanzees, ar3k;kev)2y2+ mf4 d hkffip g:de more likely to have similar base sequences. Over time, as species diverge and evolve, mutations accumulate in their base sequences. The longer two species have been separated from their common ancestor, the more mutations will have accumulated in their genomes. Therefore, species that are closely related have fewer accumulated mutations and more similar base sequences (Choice B).Choice A is incorrect because genome size is not necessarily proportional to the size of the species. The genome size can vary significantly even among organisms of similar size, and organisms with similar-sized genomes, such as the horse and mouse vary greatly in size. Choice C is incorrect because it is possible to have a larger genome size with a comparable, or even smaller, number of genes, depending on the amount of non-coding DNA and repetitive sequences present in the genome. Humans have a larger genome but a similar number of genes to the chimpanzee, mouse and horse. Choice D is incorrect because although the nucleotide base sequence in the tabl d:+fdgi3 2fky4 v)kh2p fme;ke for humans and chimpanzees is the same it does not mean that their whole genome is the same.
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