A cytogeneticist examining cells in Tradescantia stamen hairs is trying to deter

Question

A cytogeneticist examining cells in Tradescantia stamen hairs is trying to determine the length of the various stages in mitosis and the cell cycle. She examines 1000 cells and finds 160 cells in prophase, 75 cells in metaphase, 40 cells in anaphase, and 60 cells in telophase.

a.   Assuming that the cells are sampled in proportion to the duration of each stage in the cell cycle, what percentage of the cell cycle is spent in each stage, including interphase? Show your work.

Answer:

b.   Assuming that the entire mitotic process takes place in one hour, how many hours long is one entire cell cycle? Express your answer to the nearest minute. Show your work.

Answer:

c.   This plant species is diploid, with nine chromosomes in each gamete. If the haploid concentration of DNA is designated by “X”, describe the number of chromosomes and the amount of DNA present in the cell at the end of each stage of interphase.

Explanation / Answer

a) Total number of cells = 1000

Cells in prophase = 160

cells in metaphase = 75

cells in anaphase = 40

cells in telophase = 60

cells in interphase = 1000 - (160+75+40+60) = 1000 - 335 = 665

Therefore, the percentage of cells in,

prophase = 160/1000 x 100 = 16%

metaphase = 75/1000 x 100 = 7.5%

anaphase = 40/1000 x 100 = 4%

telophase = 60/1000 x 100 = 6%

interphase = 665/1000 x 100 = 66.5%

b) When mitosis takes place in 1 hour, the entire duration of cell cycle is 24 hours. In a typical rapidly proliferating human cell, the duration of G1 phase is 11 hours, S phase is 8 hours, G2 phase is 4 hours and M phase is 1 hour.

c) The cells contain diploid number of chromosomes in interphase.If the haploid chromosomes are designated by X, the number of chromosomes present in interphase is designated by 2X.

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