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

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. In Drosophila, like in other organisms, one chromosome of each pair is inherited from each parent. Understanding the pairing of homologous chromosomes is crucial for grasping genetic recombination and the behavior of chromosomes during meiosis.

Prophase I of Meiosis

Prophase I is the first stage of meiosis where homologous chromosomes pair up and exchange genetic material through a process called crossing over. This stage is characterized by the condensation of chromatin into visible chromosomes and the formation of tetrads, which consist of four chromatids. This pairing is essential for genetic diversity in gametes.

Genetic Recombination

Genetic recombination refers to the process by which genetic material is physically mixed during meiosis, leading to new combinations of alleles. This occurs during prophase I when homologous chromosomes exchange segments of DNA. Recombination is a key mechanism for increasing genetic variation in populations, which is vital for evolution and adaptation.