Final answer:
An inversion in a chromosome happens when a chromosomal segment breaks, flips 180 degrees, and reattaches itself in reverse order. This type of chromosomal mutation alters gene orientation but usually has milder effects unless it disrupts gene sequences. The correct option describing this mutation is (a) inversion.
Step-by-step explanation:
Understanding Chromosome Inversions
When discussing changes in a chromosome that involve the reattachment of a chromosomal fragment to the original chromosome but in the reverse order, we are referring to a type of chromosomal mutation known as an inversion. An inversion is a structural rearrangement that occurs when a segment of a chromosome breaks away, undergoes a 180° rotation (flips), and then reattaches to the same chromosome in the reversed orientation. This process does not involve the loss or gain of genetic material but changes the sequence in which genes are arranged. As a result, unless it disrupts a gene sequence, an inversion typically has milder effects compared to other types of chromosomal mutations, such as aneuploid errors.
Other chromosomal mutations include deletion (a loss of a segment), duplication (an extra copy of a segment), frameshift (mutation resulting from insertions or deletions of a number of nucleotides in a DNA sequence that is not divisible by three), and translocation (segment from one chromosome becomes attached to another chromosome). Inversions are essential to consider in genetics because even though they might not produce significant effects, they can lead to altered levels of gene products if regulatory elements of gene expression are moved out of position with respect to their targets.
In answering the student's question, the correct option that describes a change in a chromosome resulting from a reattachment of a chromosomal fragment to the original chromosome but in the reverse order is (a) inversion.