13.3-3ITD Most of the yeast cells in the c... [FREE SOLUTION]

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Chapter 13: 13.3-3ITD (page 264)

Most of the yeast cells in the culture were in G₁ of the cell cycle before being moved to the nutrient-poor medium. (a) How many femtograms of DNA are there in each yeast cell in G1? Estimate this value from the data in your graph. (b) How many femtograms of DNA should be present in each cell in G2? (See Concept 12.2 and Figure 12.6.) At the end of meiosis I (MI)? At the end of meiosis II (MII)? (See Figure 13.7.) (c) Using these values as a guideline, distinguish the different phases by inserting vertical dashed lines in the graph between phases and label each phase (G₁, S, G2, MI, MII). You can figure out where to put the dividing lines based on what you know about the DNA content of each phase (see Figure 13.7). (d) Think carefully about the point where the line at the highest value begins to slope downward. What specific point of meiosis does this 鈥渃orner鈥� represent? What stage(s) correspond to the downward sloping line?

Short Answer

Expert verified

(a) In the G₁ phase, 24 fg of DNA is present in each yeast cell.

(b) In the G₂ phase, 48 fg of DNA is present in each cell.

At the end of meiosis I, 24 fg of DNA is present in a yeast cell.

At the end of meiosis II, 12 fg of DNA is present in a yeast cell.

(c)

(d) The corner represents the cytokinesis of meiosis.

Step by step solution

Explanation for (a)

Yeast cells contain original genetic material before they enter the meiotic phase during poor nutrient conditions. When cells are moved to the nutrient-poor medium, they are in the G₁ phase of the cell cycle.

Thus, 24fm of DNA is present in each yeast cell in the G₁ phase of the cell cycle.

Explanation for (b)

Cell cycle comprises G1, S and G2 phase. S is the synthetic phase where the DNA content doubles. Thus, the amount of DNA in G2 will be double the amount of G1. In G2 phase, each yeast cell would have 48 fg of DNA.

In meiosis, cells divide into daughter cells with half the genetic material. At the end of meiosis I, 24 fgs of DNA would be present in each yeast cell.

In meiosis, two daughter cells further divide to produce 4 daughter cells. At the end of meiosis II, 12 fgs of DNA would be present in each yeast cell.

Explanation for (c)

Four dashed lines are drawn in the graph, dividing the cell cycle's different phases (G1, S, and G2) and MI and MII. The phases are also labeled in the graph.