The diploid number of the hypothetical animal Geneticus introductus is 2n = 36. Each diploid nucleus contains 3 ng of DNA in G₁.

Explain why a somatic cell of Geneticus introductus has the same number of chromosomes and the same amount of DNA at the beginning of mitotic prophase as one of these cells does at the beginning of prophase I of meiosis.

Key Concepts

Diploid Number

The diploid number (2n) refers to the total number of chromosomes in a somatic cell, which in this case is 36 for Geneticus introductus. This means that each somatic cell contains two sets of chromosomes, one inherited from each parent. Understanding the diploid number is crucial for comprehending how genetic information is organized and passed on during cell division.

Mitosis vs. Meiosis

Mitosis is the process of cell division that results in two identical daughter cells, each with the same number of chromosomes as the parent cell. In contrast, meiosis is a specialized form of cell division that reduces the chromosome number by half, producing gametes. At the beginning of mitotic prophase, the somatic cell has the same chromosome number and DNA content as it does at the start of prophase I of meiosis, as both processes begin with diploid cells.

DNA Content in Cell Cycle

The amount of DNA in a cell varies throughout the cell cycle. In the G₁ phase, a diploid cell contains a specific amount of DNA (3 ng in this case), which is duplicated during the S phase, leading to double the DNA content before mitosis or meiosis. However, at the beginning of mitotic prophase and prophase I of meiosis, the DNA content is effectively the same because both processes start with cells that have completed DNA replication.