27. In meiosis, an inversion in one member of a pair of homologous chromosomes will most likely lead to which
of the following?
1. Non-disjunction of the affected chromosome
2. Chromosome with duplications and deficiencies
3. Increased recombination frequency in the inverted region
4. Mispairing of the affected chromosome with a non-homologous chromosome

Chromosome Inversion During Meiosis: Causes of Duplications and Deficiencies

Chromosome inversions are structural rearrangements where a segment of a chromosome is reversed end to end. When such an inversion occurs in one member of a pair of homologous chromosomes, and meiosis begins, the result can be more than just altered gene order — it can affect the offspring genetically in profound ways.

Let’s walk through the key biological process and outcome.

What Is a Chromosomal Inversion?

• An inversion occurs when a chromosome segment breaks off, flips around, and reattaches in the opposite orientation.

• Two main types:

  • Paracentric: Does not include the centromere.

  • Pericentric: Includes the centromere.

What Happens in Meiosis?

During meiosis I, homologous chromosomes pair up for recombination. If one of the chromosomes has an inversion, looping must occur to allow homologous regions to align. This misalignment sets the stage for complications.

Key Consequences of Crossing Over in Inverted Regions

When crossing over occurs within the looped inversion segment:

• It leads to recombinant chromatids with duplications and deletions.

• These unbalanced chromosomes can result in non-viable gametes or cause developmental abnormalities in the offspring.

Let’s Evaluate the Options:

1. Non-disjunction of the affected chromosome

   • Not directly caused by inversion; more common with centromere abnormalities or spindle errors.

2. Chromosome with duplications and deficiencies

   • ✅ Correct Answer

   • This is the most likely result due to improper alignment and recombination in the inversion loop.

3. Increased recombination frequency in the inverted region

   • False. Recombination is actually suppressed in the inversion loop to prevent unbalanced gametes.

4. Mispairing of the affected chromosome with a non-homologous chromosome

   • False. Pairing still occurs with its homolog, just abnormally through loop formation.

✅ Correct Answer:

(2) Chromosome with duplications and deficiencies

Why This Is Important

Chromosomal inversions and their meiotic consequences are crucial in:

• Genetic counseling

• Evolutionary biology (as some inversions can provide adaptive advantages)

• Understanding miscarriages and genetic diseases

In research and diagnostics, identifying inversion-induced duplications and deletions helps detect the genetic basis of many conditions.

Understanding these dynamics is key to unraveling the complexities of chromosomal behavior and inheritance.