In a mouse cell at the start of mitosis, how many chromatids are present?
Since Jiskha doesn't have a biology expert at this time, please try posting your question at this site.
http://www.biology-online.org/biology-forum/
To determine the number of chromatids in a mouse cell at the start of mitosis, we need to understand the basics of mitosis and the structure of chromatids.
Mitosis is the process by which a cell divides and produces two identical daughter cells. It consists of several phases, including prophase, metaphase, anaphase, and telophase. During prophase, the DNA condenses and organizes into chromosomes. Each chromosome consists of two identical sister chromatids held together by a structure called the centromere.
However, at the start of mitosis, during the interphase (the phase before mitosis), the DNA replicates in a process called DNA synthesis (or S phase). As a result, each chromosome is duplicated, and each sister chromatid is formed. So, before mitosis, the number of chromatids in a cell is twice the number of chromosomes.
In mice, like in humans, the typical chromosomal number is 40 in their somatic cells. Therefore, in a mouse cell at the start of mitosis, there would be 80 chromatids present, as each of the 40 chromosomes has been duplicated during DNA synthesis.
To summarize, in a mouse cell at the start of mitosis, there are typically 80 chromatids present, as each of the 40 chromosomes has duplicated during the interphase.