The 1 Kb DNA ladder is mixture of
What will be an ideal response?
DNA fragments of known size that are used for size estimation.
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Enzymes are
(a) biological catalysts. (b) agents that speed up cellular reactions. (c) proteins. (d) all of the above.
Which of the following statements describes the hypothesis proposed to explain the regular arrangement of leaves around the stem?
A. Primordia are pre-programmed to grow in a set arrangement. B. Primordia are unable to communicate. C. Chemical signals from developing leaf primordia create regions preventing new primordial growth. D. Developing leaf primordia physically block new primordial. E. We do not currently have a hypothesis to explain how these growth patterns occur.
In order to infect a cell, a virus must
A. have a special protein on its surface that can interact with a protein on the surface of the host cell. B. produce a special extension of its cytoplasm when it comes into contact with the appropriate host cell. C. actively burrow through the cell wall or cell membrane of the host cell to reach the cell's nucleus. D. inject its protein into the cell while the nucleic acid remains attached to the host cell surface.
Scientists can determine the size of DNA fragments through a process known as gel electrophoresis. In this process, DNA is loaded into a gel submerged in a liquid buffer through which an electric current is run. Large DNA molecules move slower and can be observed at the top of the gel, whereas smaller DNA fragments move faster (and are seen at the bottom of the gel). Based on what you know about the properties of DNA, how is the electric current arranged in this process?
a. Since DNA is negatively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel. b. Since DNA is negatively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel. c. Since DNA is positively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel. d. Since DNA is positively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel. e. Since DNA is uncharged, the placement of the positive end and negative end does not matter.