NASA has discovered an alien life-form. You are called in to help NASA scientists to deduce the genetic code for this alien
Surprisingly, this alien life-form shares many similarities with life on Earth: this alien uses DNA as its genetic material, makes RNA from DNA, and reads the information from RNA to make protein using ribosomes and tRNAs. Even more amazing, this alien uses the same 20 amino acids, like the organisms found on Earth, and also codes for each amino acid by a triplet codon. However, the scientists at NASA have found that the genetic code used by the alien life-form differs from that used by life on Earth. NASA scientists drew this conclusion after creating a cell-free protein-synthesis system from alien cells and adding an mRNA made entirely of uracil (poly U). They found that poly U directs the synthesis of a peptide containing only glycine. NASA scientists have synthesized a poly AU mRNA and observe that it codes for a polypeptide of alternating serine and proline amino acids. From these experiments, can you determine which codons code for serine and proline? Explain.
Bonus question. Can you propose a mechanism for how the alien's physiology is altered so that it uses a different genetic code from life on Earth, despite all the similarities?
No, you cannot definitively determine the codons that code for serine or proline, because it could be either UAU or AUA.
Bonus. The alien aminoacyl-tRNA synthetases could adapt a different amino acid to each tRNA, thus matching an amino acid with a different codon compared with the codons used by life on Earth.
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If a C3 plant that normally closes its stomata during hot, dry conditions were triggered to open them instead, the most likely outcome would be that
A. CO2 enters the leaf, decreasing the rate of photosynthesis. B. More chlorophyll is made, increasing the rate of photosynthesis. C. Glucose leaves the leaf, increasing the rate of photosynthesis. D. O2 enters the leaf, increasing the rate of photosynthesis. E. Water leaves the leaf, decreasing the rate of photosynthesis.
Four of the five answers listed below are bound by membranes. Select the exception
a. mitochondria b. ribosome c. peroxisome d. nucleus e. lysosome
Which of the following is a not one of the major reasons why women are less likely than men to enter treatment?
A. lack of family support B. obligation of child-rearing C. lack of gender specific treatment programs D. partner support
Micronutrients
A) benefit organisms if they are present but are not essential.
B) are not naturally occurring and must be synthesized by scientists.
C) are needed in smaller quantities than are macronutrients.
D) include water, carbon, nitrogen, and phosphorus.
E) are smaller molecules than are macronutrients.