Question at position 45 What happened to this chromosome? Chromosomal sections are indicated by letter. Original: ABCDEFG Mutant: ABEDCFGnondisjunctioninversionduplicationtranslocationdeletion单项选择题
A
nondisjunction
B
inversion
C
duplication
D
translocation
E
deletion

Question

Question at position 45 What happened to this chromosome? Chromosomal sections are indicated by letter. Original: ABCDEFG Mutant: ABEDCFGnondisjunctioninversionduplicationtranslocationdeletion

BlackTom AI · Accepted Answer

Here is what the question is asking: Given Original: ABCDEFG and Mutant: ABEDCFG, identify what happened to the chromosome that caused this change in order.
Option 1: nondisjunction. This option describes failure of homologous chromosomes to separate during meiosis, which typically results in cells with an extra copy or missing copy of a chromosome (aneuploidy). It does not explain a rearrangement of internal gene order like ABEDCFG; it would not simply reorder letters while keeping all seven letters present in the same counts. Therefore this is not consistent with the observed pattern.
Option 2: inversion. An inversion is when a chromosome segment flips its orientation. If the segment CDE were inverted, it would become EDC, yielding ABEDCFG when applied to the original ABCDEFG. This directly accounts for the reversal in the middle portion while all letters remain present, matching the mutant sequence.
Option 3: duplication. Duplication involves copying a segment, producing extra letters in that region (e.g., an extra CDE or similar), which would change copy number rather than simply reversing order. The mutant still shows every letter once, so duplication cannot explain the change.
Option 4: translocation. A translocation moves a segment from one chromosome to another chromosome, changing chromosome identity or location, not just the internal order of letters within the same chromosome. Since the mutant version only changes order and not the overall set of letters, translocation is unlikely.
Option 5: deletion. Deletion removes a segment, leading to missing letters from the chromosome, but the mutant ABEDCFG contains all seven letters A through G once. Therefore deletion cannot account for the observed sequence.
Summarizing, only inversion provides a plausible mechanism that rearranges the internal order of a region (CDE to EDC) without altering the overall gene content, matching the mutant ABEDCFG pattern.

Question at position 45 What happened to this chromosome? Chromosomal sections are indicated by letter. Original: ABCDEFG Mutant: ABEDCFGnondisjunctioninversionduplicationtranslocationdeletion单项选择题

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