BCHM 4360 QUESTIONS & ANSWERS
HB: What is the main question being addressed?
Is there regularity to the positioning of the histones in DNA?
HB: What is the experimental approach for Figure 1?
-rat liver nuclei were incubated in the presence of CaCl2 and MgCl2 for 0, 20, 40, 60,
and 80 min
-performed polyacrylamide gel electrophoresis of rat liver nuclear DNA that was
digested by the Ca-Mg endonuclease
HB: What does the data from Figure 1 indicate?
-Ca-Mg endonuclease is activated by calcium and magnesium ions
-the longer time spent incubating in the presence of CaCl2 and MgCl2, the more DNA in
the bands representing the lower molecular weight species
-reached a limit pattern quickly (fragments could not get smaller than a certain size even
with longer incubation)
-bands are regularly spaced
HB: What is the experimental approach for Figure 2?
-distance of the band from origin of the gel was plotted on the y axis (log scale)
-square root of the mobility of the bands were plotted on the x axis
HB: What does the data from Figure 2 indicate?
-graph is a linear line
-their molecular weights are multiples of the molecular weight of the smallest species
HB: What is the experimental approach for Figure 3?
-Ca-Mg endonuclease was extracted from rat liver nuclei using KCl, K-phosphate,
ethylene glycol and dialysing into tris, MgCl2, ethylene glycol, 2-mercaptoethanol, and
HCl (crude enzyme)
-extract was incubated with calf thymus DNA in the presence of CaCl2 for 0, 45, 90, and
120 min
-performed polyacrylamide gel electrophoresis of calf thymus DNA that was digested by
the Ca-Mg endonuclease
HB: What does the data from Figure 3 indicate?
HB: What is the main question being addressed?
Is there regularity to the positioning of the histones in DNA?
HB: What is the experimental approach for Figure 1?
-rat liver nuclei were incubated in the presence of CaCl2 and MgCl2 for 0, 20, 40, 60,
and 80 min
-performed polyacrylamide gel electrophoresis of rat liver nuclear DNA that was
digested by the Ca-Mg endonuclease
HB: What does the data from Figure 1 indicate?
-Ca-Mg endonuclease is activated by calcium and magnesium ions
-the longer time spent incubating in the presence of CaCl2 and MgCl2, the more DNA in
the bands representing the lower molecular weight species
-reached a limit pattern quickly (fragments could not get smaller than a certain size even
with longer incubation)
-bands are regularly spaced
HB: What is the experimental approach for Figure 2?
-distance of the band from origin of the gel was plotted on the y axis (log scale)
-square root of the mobility of the bands were plotted on the x axis
HB: What does the data from Figure 2 indicate?
-graph is a linear line
-their molecular weights are multiples of the molecular weight of the smallest species
HB: What is the experimental approach for Figure 3?
-Ca-Mg endonuclease was extracted from rat liver nuclei using KCl, K-phosphate,
ethylene glycol and dialysing into tris, MgCl2, ethylene glycol, 2-mercaptoethanol, and
HCl (crude enzyme)
-extract was incubated with calf thymus DNA in the presence of CaCl2 for 0, 45, 90, and
120 min
-performed polyacrylamide gel electrophoresis of calf thymus DNA that was digested by
the Ca-Mg endonuclease
HB: What does the data from Figure 3 indicate?
