When separating DNA fragments by gel electrophoresis, what is the purpose of including molecular weight markers?
A. Markers provide an indication as to the total number of restriction fragments on the gel.
B. Markers are used as a control to determine the relative size of restriction fragments.
C. Markers are needed to estimate the relative charges on each of the restriction fragments.
D. Markers ensure that fragments having a greater molecular weight migrate at the same rate as those having a lighter molecular weight.
Answer: B
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Oral rehydration solutions that contain both salt and glucose are highly effective in treating severe dehydration caused by diarrhea and vomiting. However, glucose or salt alone are not effective. This is because water passively follows
A. sodium and glucose, which are cotransported across the gastrointestinal epithelium. B. glucose and sodium, which are transported by facilitated diffusion. C. glucose, which provides the energy for the active transport of salt. D. ATP, which is required to transport sodium unless glucose is available for cotransport. E. glucose that is broken down quickly in the mouth by saliva and cotransported with salt via diffusion across the epithelial cells of the oral cavity.
In Morgan's testcross of a gray-bodied, long-winged heterozygous female Drosophila with a homozygous recessive black-bodied, vestigial-winged male, the following offspring were obtained: 965 gray body, long wing; 944 black body, vestigial wing; 206 gray body, vestigial wing; 185 black body, long wing. Focusing only on the recombinant classes (gray body, vestigial wing and black body, long wing), the numbers of offspring of each type are similar (206 and 185). What accounts for the similar number of offspring of each recombinant phenotype?
A cell divides to produce two daughter cells that are genetically identical
A. The statement is true for mitosis only. B. The statement is true for meiosis I only. C. The statement is true for meiosis II only . D. The statement is true for mitosis and meiosis I. E. The statement is true for mitosis and meiosis II.
Cyanide poisoning prevents the production of ATP. If ATP were not available to drive the sodium-potassium pump, which of the following is most likely?
A) K+ concentrations inside the cell will increase causing hyper polarization. B) Na+ concentration inside the cell will decrease causing depolarization. C) Na+ will leak back into the cell and bring water with it causing cells to burst. D) The voltage of the membrane will be unchanged.