A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):
Chromosome 1RNMDHBGKWU
Chromosome 2RNMDHBDHBGKWU
How does the pairing diagrammed in part (b) differ from the pairing of chromosomes in an inversion heterozygote?

Verified step by step guidance

1. Examine the given chromosome sequences: Chromosome 1 (RNMDHBGKWU) and Chromosome 2 (RNMDHBDHBGKWU). Note that Chromosome 2 contains a duplication of the segment 'DHBG'.
2. Understand the concept of an inversion heterozygote: In an inversion heterozygote, one homologous chromosome contains a segment that has been inverted (flipped in orientation) compared to the other homologous chromosome.
3. Compare the given pairing to an inversion heterozygote: In the given pairing, the difference is due to a duplication of a segment ('DHBG') in Chromosome 2, not an inversion. In an inversion heterozygote, the homologous chromosomes would align with a loop structure to accommodate the inverted segment.
4. Describe the structural difference: In the given pairing, the chromosomes align without forming a loop because the difference is a duplication, not an inversion. In contrast, an inversion heterozygote would require a loop to align the inverted segment with its homologous counterpart.
5. Conclude the comparison: The pairing in the given problem differs from an inversion heterozygote because it involves a duplication rather than an inversion. The structural adjustment (loop formation) seen in inversion heterozygotes is not necessary here.

Key Concepts

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same genes at the same loci but may carry different alleles. In Drosophila, these chromosomes can undergo various structural changes, including inversions, which can affect gene expression and pairing during meiosis.

Inversion Heterozygote

An inversion heterozygote is an individual that has one normal chromosome and one chromosome with a segment inverted. This structural alteration can disrupt normal pairing during meiosis, leading to potential issues in gamete formation, such as the production of unbalanced gametes due to improper crossing over.

Meiotic Pairing

Meiotic pairing refers to the alignment of homologous chromosomes during meiosis, which is crucial for accurate segregation of genetic material. In the presence of inversions, the pairing may be altered, leading to unique configurations that can affect genetic recombination and the viability of gametes.