A study of the human gut performed in 1982 used various types of plates under different growth conditions to describe and enumerate the microbes in the human gut. They concluded that the majority of the microbes in the human gut are Gammaproteobacteria
A study conducted in 2010 using next-generation sequencing to characterize 16S rRNA sequences concluded that the majority of the microbes in the human gut are Firmicutes and Bacteriodetes. Why did these studies have different conclusions? Which study do you think is most accurate?
What will be an ideal response?
Answer: The studies do not agree because of enrichment / culture bias. Many organisms are easy to grow in the lab and grow faster than other organisms on agar plates or liquid media. Some of the most numerous organisms in the environment or the human body do NOT grow well, or they do NOT grow AT ALL in the lab conditions tested so far. This creates a biased view of microbial community composition. The first study suffered from culture bias. Gammaproteobacteria tend to be very easy to grow in the lab. The second study is probably more accurate, as it is based on sequencing nucleic acid directly and circumvents growth of the organisms in order to detect them.
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Fill in the blank with the appropriate word.
James Watson and Francis Crick ____
a. were both English researchers working at Cambridge University b. performed elegant experiments in DNA chemistry c. constructed an accurate model of DNA’s double helix structure d. performed experiments that convinced scientists that DNA is a double-stranded molecule e. used x-ray diffraction in all of their experiments
Which of the following is a sign that scientific information on a website may be unreliable?
A) The site avoids anecdotal evidence. B) The site backs up its claims with references to primary sources. C) A reputable medical establishment maintains the site. D) The site is set up to allow you to buy the product being described.
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be
A) 0.25x B) 0.5x C) x. D) 2x. E) 4x.