Mice ( Mus musculus ) have 40 chromosomes per diploid cell (2n=40). How many dou
ID: 50809 • Letter: M
Question
Mice (Mus musculus) have 40 chromosomes per diploid cell (2n=40). How many double- stranded DNA helices, and how many chromosomes are there in a mouse cell that is in the G1 stage of the cell cycle?
80 DNA helices and 40 chromosomes
40 DNA helices and 40 chromosomes
40 DNA helices and 80 chromosomes
40 DNA helices and 20 chromosomes
80 DNA helices and 80 chromosomes
80 DNA helices and 40 chromosomes
40 DNA helices and 40 chromosomes
40 DNA helices and 80 chromosomes
40 DNA helices and 20 chromosomes
80 DNA helices and 80 chromosomes
Explanation / Answer
Their are two kinds of cell divisions/cell cycle taking place in a cell. They are known as mitosis and meiosis. Mitosis usually takes place in the somatic cells and meiosis takes place in the germ cells. In this particular question we are talking about mitosis. Their is a phase of cell cycle which preclused mitosis and is known as interphase. In this phase the cell actually prepares the chromosomes to replicate and then divide faithfully during mitosis. So interphase can be termed as the preperatory phase followed by mitosis (the actual chromosome seperation actually takes here). The interphase has been divided into mainly three phases namely G1, S and G2 phase. In the G1 phase the cell produces mRNA and proteins which would be required for faithful DNA replication as well as cell division (cytokinesis) later. It is the S phase where actual DNA replication takes place followed by G2 phase where the cell readies itself for mitosis. Thus, with respect to the question there should be 40 chromosomes (same as the diploid number) as their has been no DNA replication which would lead to duplication of chromosomes. Since every chromosome corresponds to a single double stranded DNA helix, the number of double helices would also be 40. Hence the correct answer would be option two "40 DNA helices and 40 chromosomes".
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