Why are two selectable markers present in the target vector used for making mouse gene knockouts?
What will be an ideal response?
Two selectable markers are used for making mouse gene knockouts because there is a high level of random integration of the target vector into the mouse genome. One of the selectable markers selects for the gene knockout, while the other selects against transformants in which the target vector may have integrated into a random location by nonhomologous recombination.
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Oxygen (O2) makes up about 21% of the Earth's atmosphere. The graph below depicts changes in atmospheric O2 levels measured between the years 1990 and 2008. The burning of fossil fuels produces CO2, removing O2 from the atmosphere
It has been estimated that approximately three molecules of O2 are consumed by every single molecule of CO2 produced by fossil fuel combustion. Over about 20 years, a total loss of 0.0317% O2 from the atmosphere was calculated from this data. If you compare this graph to that shown in Figure 25.1, how is the trend in O2 levels related to the trend in CO2 levels? A. Both O2 levels and CO2 levels increase over time. B. Both O2 levels and CO2 levels decrease over time. C. O2 levels decrease as CO2 levels increase. D. O2 levels increase as CO2 levels decrease.
Diatoms reproduce by:
A. binary fission B. a sporic life cycle C. a gametic life cycle D. a zygotic life cycle E. spontaneous generation
The electron transfer chain is located
a. on the inner membrane of the mitochondria. b. on the inner membrane of the chloroplasts. c. in the fluid part of the chloroplast. d. throughout the cytoplasm of the cell. e. on the plasma membrane of eukaryotes.
In which part of the chloroplast do the carbon fixation reactions take place?
a. lumen b. stroma c. granum d. mesophyll e. thylakoids