Chromosomal Mutations or Aberrations: Inversion

Inversion is a type of structural chromosomal mutation in which a segment of a chromosome breaks, rotates through 180°, and rejoins so that the gene sequence within that segment is reversed.

There is no net gain or loss of genetic material in the original inversion event; only the order of genes is changed.

Example:

• Normal gene sequence: A B C D E F G.
• After inversion, the same set of genes may occur in a different order, showing reversal and rearrangement of a segment of the chromosome.

• Inversions change the specific order of genes on a chromosome without adding or removing any genetic material.
• Crossing over within an inversion loop usually produces abnormal, non-viable chromatids, meaning mainly original parental-type combinations are recovered.
• By suppressing effective recombination, inversions help preserve and maintain specific heterozygous gene combinations.
• Recessive lethal mutations can remain safely concealed in a heterozygous state, whereas individuals with homozygous inversions are generally non-viable.

• An inversion is a structural chromosomal mutation where a segment breaks, rotates 180 degrees, and rejoins to completely reverse the original gene sequence.
• This mutational process alters the specific arrangement of genes on the chromosome without adding or removing any genetic material.
• Inversions are classified as 'paracentric' if the centromere lies outside the inverted segment and 'pericentric' if the centromere is included inside the loop.
• Crossing over within an inversion loop typically produces abnormal, non-viable chromatids, meaning primarily original parental-type combinations are recovered.
• By suppressing effective recombination, inversions help preserve specific heterozygous gene combinations and can safely conceal recessive lethal mutations.