A pair of homologous chromosomes in Drosophila has the following content (single letters represent genes):
Chromosome 1RNMDHBGKWU
Chromosome 2RNMDHBDHBGKWU
Diagram the pairing of these homologous chromosomes in prophase I.

Verified step by step guidance

1. Step 1: Understand the concept of homologous chromosomes and pairing during prophase I. Homologous chromosomes are pairs of chromosomes that have the same genes at the same loci but may have different alleles. During prophase I of meiosis, homologous chromosomes pair up and align gene by gene to form a structure called a synaptonemal complex.
2. Step 2: Compare the sequences of the two homologous chromosomes provided. Chromosome 1 has the sequence RNMDHBGKWU, while Chromosome 2 has the sequence RNMDHBDHBGKWU. Identify any differences or duplications between the two sequences.
3. Step 3: Diagram the pairing process. Start by aligning the identical regions of the two chromosomes (RNMDHBGKWU). Then, account for the extra segment (DHBG) present in Chromosome 2. This extra segment will loop out during pairing because it does not have a corresponding region on Chromosome 1.
4. Step 4: Represent the looped-out region visually. In your diagram, show Chromosome 1 and Chromosome 2 aligned gene by gene, with the extra segment (DHBG) on Chromosome 2 forming a loop. This loop is a common feature when homologous chromosomes have unequal lengths or duplications.
5. Step 5: Label the diagram clearly. Indicate the genes on each chromosome, the aligned regions, and the looped-out segment. This will help visualize the pairing of homologous chromosomes during prophase I and highlight the structural differences between them.

Key Concepts

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence but may carry different alleles. Each pair consists of one chromosome inherited from each parent, and during meiosis, they align closely during prophase I, allowing for genetic recombination through crossing over.

Meiosis and Prophase I

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid cells. Prophase I is the first stage of meiosis where homologous chromosomes pair up and exchange genetic material through a process called crossing over, which increases genetic diversity in the resulting gametes.

Genetic Recombination

Genetic recombination is the process by which genetic material is physically mixed during meiosis, particularly during prophase I when homologous chromosomes exchange segments. This process creates new combinations of alleles, contributing to genetic variation in offspring, which is essential for evolution and adaptation.