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Chapter 2: Problem 19

The nuclear DNA content of a single sperm cell in Drosophila melanogaster is approximately 0.18 picogram. What would be the expected nuclear DNA content of a primary spermatocyte in Drosophila? What would be the expected nuclear DNA content of a somatic cell (non-sex cell) in the Gl phase? What would be the expected nuclear DNA content of a somatic cell at metaphase?

Short Answer

Expert verified
Answer: The expected nuclear DNA content is 0.36 picogram for a primary spermatocyte and a somatic cell in the G1 phase, and 0.72 picogram for a somatic cell at metaphase.

Step by step solution

01

Understand the DNA content in different cells and stages

First, we need to comprehend how the DNA content changes in different cells at various stages. In a sperm cell, the DNA content is haploid (having half the DNA content), while a somatic cell has diploid DNA content (double the sperm cell). Mitosis has a G1 phase, where the cell has diploid content and a metaphase with doubled DNA content since it has replicated its DNA during the S phase.
02

Calculate the DNA content of a primary spermatocyte

A primary spermatocyte is generated through meiosis, which begins with a diploid parental cell. Since a sperm cell has half the DNA content of a diploid cell, we can calculate the nuclear DNA content of the primary spermatocyte by multiplying the sperm cell's DNA content by 2. Given DNA content of sperm cell = 0.18 picogram Expected nuclear DNA content of primary spermatocyte = 0.18 picogram * 2 = 0.36 picogram
03

Calculate the DNA content of a somatic cell in G1 phase

A somatic cell in the G1 phase has a diploid DNA content, which is the same as a primary spermatocyte. So, the expected nuclear DNA content of a somatic cell in the G1 phase will be 0.36 picogram.
04

Calculate the DNA content of a somatic cell at metaphase

A somatic cell at metaphase has replicated its DNA during the S phase, doubling its DNA content. Since G1 phase has diploid content (0.36 picogram), the DNA content at metaphase will be: Expected nuclear DNA content of a somatic cell at metaphase = 0.36 picogram * 2 = 0.72 picogram In summary, the expected nuclear DNA content is as follows: 1. Primary spermatocyte - 0.36 picogram 2. Somatic cell in the G1 phase - 0.36 picogram 3. Somatic cell at metaphase - 0.72 picogram

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Most popular questions from this chapter

Contrast the chromatin fiber with the mitotic chromosome. How are the two structures related?

Define and discuss these terms: (a) synapsis, (b) bivalents, (c) chiasmata, (d) crossing over, (e) sister chromatids, (f) tetrads, \((g)\) dyads, (h) monads.

In this chapter, we focused on how chromosomes are distributed during cell division, both in dividing somatic cells (mitosis) and in gamete- and spore- forming cells (meiosis). We found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, answer the following questions. (a) How do we know that chromosomes exist in homologous pairs? (b) How do we know that DNA replication occurs during interphase, not early in mitosis? (c) How do we know that mitotic chromosomes are derived from chromatin?

What role do the following cellular components play in the storage, expression, or transmission of genetic information: chromatin, (b) nucleolus, (c) ribosome, (d) mitochondrion, centriole, (f) centromere?

Describe the phases of the cell cycle and the events that characterize each phase.
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