Question

In prophase I, the cell begins to ______. The chromosomes ______ up, forming a structure called a ______, which contains ______ chromatids. As homologous chromosomes pair up and form a tetrad, they undergo a process called ______-______. First, the ______ of the homologous chromosomes cross over one another. Then, the _______ sections of the chromatids are exchanged. Crossing-over is important because it produces new combinations of ______ in the cell.

Answer 1

In prophase I, the cell begins to divide. The chromosomes condense up, forming a structure called a bivalent or tetrad, which contains two chromatids. As homologous chromosomes pair up and form a tetrad, they undergo a process called crossing - over. First, the non-sister chromatids of the homologous chromosomes cross over one another. Then, the corresponding sections of the chromatids are exchanged. Crossing-over is important because it produces new combinations of alleles in the cell.

Step-by-step explanation:

During prophase I of meiosis, the cell undergoes several significant changes. The chromosomes condense and become visible under a microscope. Homologous chromosomes pair up and form tetrads, which consist of two chromosomes (four chromatids) aligned side by side. This pairing allows for crossing-over to occur.

Crossing-over is a process where non-sister chromatids of homologous chromosomes exchange genetic material. This results in the swapping of sections of DNA between the chromosomes, leading to genetic recombination. Crossing-over creates new combinations of alleles on the chromatids, increasing genetic diversity within the cell.

Overall, prophase I is a crucial phase of meiosis as it allows for genetic variation to occur through the processes of chromosome pairing, crossing-over, and genetic recombination.