Question

What are inversion heterozygotes? How can meiotic pairing occur in these organisms? What will be the consequence?

Short answer

Answer: Inversion heterozygotes are individuals with one normal and one inverted chromosome, which they inherited from a parent with a chromosome inversion. Meiotic pairing occurs in these organisms through the formation of an inversion loop, allowing the chromosomes to align and recombine properly. However, this process can lead to the production of abnormal gametes, lower recombination rates, and reduced fertility.

Step-by-step solution

1. Chromosome Inversions

Chromosome inversions occur when a section of a chromosome breaks off, flips around and reattaches itself to the same chromosome. This results in the affected region being present in reverse order compared to the normal orientation. There are two types of inversions: paracentric (doesn't include centromere) and pericentric (includes centromere).

2. Inversion Heterozygotes

Inversion heterozygotes have one chromosome with the normal orientation of the DNA sequence and the other chromosome with an inverted DNA sequence. These individuals are heterozygous for the inversion, as they have one normal and one inverted chromosome.

3. Meiotic Pairing in Inversion Heterozygotes

During meiosis, homologous chromosomes need to pair with each other to allow recombination and exchange genetic information. In inversion heterozygotes, pairing can occur between the normal and inverted chromosomes by forming a loop-like structure where the two chromosomes align in the inverted regions. This process is known as the formation of an inversion loop, which allows the chromosomes to align and recombine properly.

4. Consequences of Meiotic Pairing in Inversion Heterozygotes

Although inversion loops help create correct chromosome alignment during meiosis, mistakes in repair or recombination can lead to the production of abnormal gametes. These gametes may have chromosome duplications or deletions, which can cause serious consequences for the offspring if fertilization occurs. Additionally, inversion heterozygotes may have lower fertility rates as a result of lowered recombination rates, especially if the inversion is large and affects many genes. In summary, inversion heterozygotes are individuals with one normal and one inverted chromosome, which they inherited from a parent with a chromosome inversion. Meiotic pairing can occur in these organisms through the formation of an inversion loop. The consequence of meiotic pairing in inversion heterozygotes can include the production of abnormal gametes, lower recombination rates, and reduced fertility.