Describe how and why DNA replication is semidiscontinuous
What will be an ideal response?
Ans: The two strands of a DNA duplex are replicated in different ways as a single replication fork opens in one direction. A DNA polymerase can only synthesis a new DNA polynucleotide in the 5?-3? direction. The duplex is antiparallel, however, so only one strand (the leading strand) is replicated continuously. The other (lagging) strand is replicated discontinuously in a series of short pieces (Okazaki fragments). These fragments are synthesized in the 5?-3? direction but are assembled in the 3?-5? direction as the replication fork proceeds.
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The microbiologist receives a sputum specimen that upon preliminary Gram staining review of direct smear, contains numerous squamous epithelial cells and an excessive amount of contami-nating normal flora. Based on the microbiologists knowledge, the microbiologist rejects the spe-cimen and requests a new sample. The physician insists that the microbiologist culture the sample as received. The
microbiologist should: a. disregard the physicians request and dis-card the specimen. b. notify their supervisor and write-up the physician. c. set-up the culture as ordered noting the lack of specimen integrity that may com-promise culture results. d. the microbiologist should have not called the physician and process the sample as received.
Why are endospores so dangerous to food production? What will be an ideal response?
You are in lab attempting to prepare a slide of cow blood for observation in a wet mount. You place a small drop of the blood on a slide, add a drop of strong saline (salt) solution, and then cover all of it with a coverslip. After returning to your desk, you observe the slide with your microscope and notice that all of the red blood cells (RBCs) do not look like the nice round donut shaped cells in your lab manual. Instead, the RBCs look very shriveled up. Your lab partner has also made a slide, but the RBCs on their slide do look like the ones in the lab manual; your lab partner used a more dilute solution of saline but the same vial of blood. What is the most plausible explanation for the appearance of the blood cells on your slide?
a. The saline you used was hypotonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane mostly into the cells. b. The saline you used was isotonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane into and out of the cells at an equal rate. c. The saline you used was hypertonic to the RBCs; this resulted in water osmosing through the RBC plasma membrane mostly out of the cell. d. The RBCs were hypertonic to the saline; this resulted in water osmosing through the RBC plasma membrane mostly into the cells.
The fact that energy transformations increase the amount of entropy is the basis of which of the following?
a. cell theory b. first law of thermodynamics c. second law of thermodynamics d. oxidation-reduction reactions