Chapter 18, Problem 14Q

A.

Summary Introduction

To explain: All cells including all their phases in their cell cycle are expected to contain radioactive DNA after labeling procedure.

Concept introduction: Cells are cultured in culture mediums that contain all the necessary nutrients for the cell to grow and divide. Cells that are tested for cell cycle are usually loaded with nucleotides to assess the S phase of the experiment. The DNA is usually found as chromatin reticulum, fine thread-like structures in the nucleus during interphase. When the cell is about to divide, the chromosome undergoes condensation to compact its structure. This structure when stained with suitable dyes is visible during the M phase of the cell cycle. Autoradiography is a technique where the nucleotides are radiolabelled with radioactive isotope of an atom present in them, mostly nitrogen or carbon isotope. These radiolabelled nucleotides when they are incorporated into the DNA during cell division emit radiation.  The radioactivity is captured using photographic emulsion. This photographic emulsion when placed over the cells, the radioactive isotope activates the emulsion and wherever the radioactivity is exhibited black dots are observed in the emulsion.

B.

Summary Introduction

To explain: The reason why initially there were no mitotic cells that possessed radioactive DNA.

Concept introduction: Cells are cultured in culture mediums that contain all the necessary nutrients for the cell to grow and divide. Cells that are tested for cell cycle are usually loaded with nucleotides to assess the S phase of the experiment. The DNA is usually found as chromatin reticulum, fine thread-like structures in the nucleus during interphase. When the cell is about to divide, the chromosome undergoes condensation to compact its structure. This structure when stained with suitable dyes is visible during the M phase of the cell cycle. Autoradiography is a technique where the nucleotides are radiolabelled with radioactive isotope of an atom present in them, mostly nitrogen or carbon isotope. These radiolabelled nucleotides when they are incorporated into the DNA during cell division emit radiation.  The radioactivity is captured using photographic emulsion. This photographic emulsion when placed over the cells, the radioactive isotope activates the emulsion and wherever the radioactivity is exhibited black dots are observed in the emulsion.

C.

Summary Introduction

To explain: The rise and fall and again the rise of the curve.

Concept introduction: Cells are cultured in culture mediums that contain all the necessary nutrients for the cell to grow and divide. Cells that are tested for cell cycle are usually loaded with nucleotides to assess the S phase of the experiment. The DNA is usually found as chromatin reticulum, fine thread-like structures in the nucleus during interphase. When the cell is about to divide, the chromosome undergoes condensation to compact its structure. This structure when stained with suitable dyes is visible during the M phase of the cell cycle. Autoradiography is a technique where the nucleotides are radiolabelled with radioactive isotope of an atom present in them, mostly nitrogen or carbon isotope. These radiolabelled nucleotides when they are incorporated into the DNA during cell division emit radiation.  The radioactivity is captured using photographic emulsion. This photographic emulsion when placed over the cells, the radioactive isotope activates the emulsion and wherever the radioactivity is exhibited black dots are observed in the emulsion.

D.

Summary Introduction

To estimate: The length of G2 phase from the graph obtained.

Concept introduction: Cells are cultured in culture mediums that contain all the necessary nutrients for the cell to grow and divide. Cells that are tested for cell cycle are usually loaded with nucleotides to assess the S phase of the experiment. The DNA is usually found as chromatin reticulum, fine thread-like structures in the nucleus during interphase. When the cell is about to divide, the chromosome undergoes condensation to compact its structure. This structure when stained with suitable dyes is visible during the M phase of the cell cycle. Autoradiography is a technique where the nucleotides are radiolabelled with radioactive isotope of an atom present in them, mostly nitrogen or carbon isotope. These radiolabelled nucleotides when they are incorporated into the DNA during cell division emit radiation.  The radioactivity is captured using photographic emulsion. This photographic emulsion when placed over the cells, the radioactive isotope activates the emulsion and wherever the radioactivity is exhibited black dots are observed in the emulsion.