AST 248: The Search for Life in the Universe

1. How many different protein monomers are found in living organisms on the Earth? How many different proteins are found in living organisms? About 20 amino acid monomers are used in living systems. About 100,000 different proteins are found.
2. Life as we know it uses 4 different kinds of bases in the composition of DNA. Suppose in another form of life there were 6 different kinds of bases utilized in the structure of DNA. Assuming both forms of life use approximately 20 - 22 different amino acids, how many base-pairs would be needed to encode these amino acids in this alternate life, i.e., what would the length of a codon in numbers of base-pairs? If you don't understand the meanings of any of these terms, use the internet or your texts to explain them. Show your work. The length of a codon would be 2 since 6² is 36 which is greater than 20. The question should have more clearly stated the request as: How many base-pairs would be needed in a single codon to encode 20 amino acids.
3. Find, by searching the web, the organism with the shortest length of an individual DNA molecule and the organism with the longest. Provide the URLs to document your findings. Candidatus Carsonella ruddii with 159,662 base pairs has the smallest genome of any characterised bacteria, but appears to be missing several genes essential for life, so perhaps this organism should be considered an organelle. Mycoplasma genitalium, which has the smallest genome of any free-living organism, has a genome of 580,000 base pairs. Nanoarchaeum equitans has a genome 490,885 base-pairs long but may not be free-living. Viruses have shorter DNA but are not free-living (give half credit). Amoeba dubia has the largest genome at 700pg.
4. Describe how construction of sugars (photosynthesis) and respiration occurred in environments lacking free oxygen and sunlight. anerobic (sulfur) photosynthesis 2H₂S + CO₂ = CH₂O + 2S + H₂O and fermentation for respiration 2(CH₂O)_n = nCH₄ + nCO₂ + energy
5. What evidence exists linking thermophiles with the earliest life forms on the Earth? Most deeply diverging lineages in bacteria and archaea are thermophiles; also, for the first billion or more years after life arose on it.
6. This question concerns extremophiles.
   1. What are two general energy sources for extremophiles? inorganic chemicals, volcanic heat
   2. What are two general sources of carbon for extremophiles? CO₂ and organic compounds