Give several pieces of evidence that RNA preceded proteins and DNA in living things. Do your answers to (1) mean that the first life was RNA-based, with RNA serving as both the catalyst and the genetic material? Briefly discuss the strengths and weaknesses of this hypothesis. It is believed that the machinery for photosynthesis evolved only once, in the cyanobacteria. However, several unrelated groups of eukaryotes, such as green plants, diatoms, and euglenoids, are able to photosynthesize. How can this be explained? Answer each question True or False (T/F). If the answer is false, explain why. Eukaryotic cells are more similar to archaea for genes involved in protein synthesis and DNA replication, but more similar to bacteria for genes involved in metabolism. RNA has been found in meteorites, and was produced in the Miller- Urey experiment, giving evidence supporting the \"RNA-first\" hypothesis of the origin of life. The last universal common ancestor of all living things lived less than 2 billion years ago. The first living things required oxygen (O_2). The^12C/^13C ratio is higher in living things than in atmospheric CO_2. Which of the following is your closest relative? Your second closest? a) a fungus; b) a dinoflagellate; c) a pine tree; d) a choanoflagellate; e) a ciliate; f) an archaean Why are marine organisms relatively common in the fossil record, but mountain-dwelling species relatively rare? Solution 1. RNA preceded proteins and DNA. This is strongly supported by the RNA World Hypothesis proposed independetly by Carl Woese, Francis Crick and Leslie Orgel in 1960s. It says that the ribosomes which are vital for protein formation are made up of RNA and the protein arrangement task during traslation is actually carried by RNA thus confirming that the early forms used RNA for their chemical reactions preceeding the use of proteins. Since RNA was instable, eventually organisms started to depend on proteins and DNA for their activities. 2. The RNA theory states that the RNA was the earliest genetic material for the early forms of life. This is due to the fact that RNA can act both as a genetic material and also as a catalyst (enzyme). Because to carry out life processes the genes need to be produced. And this production is dependent on enzymes inturn. A strong point that James Watson said is that RNA can translate into DNA in the reverse transcription process, while doing so RNA itself could have acted as an enzyme besides acting as a template to facilitate the reaction to carryout. This supports the phrase \'Life requires autocatalysis\'. The weaknesses of this hypothesis are it is highly unpredictable to have RNA nucleotides with the requirement of any enzyme. Which means RNA precursors cannot be formed without an enzyme. This conveys the message that there could have been another simple molecule which has the catalytic property and information storge system other than RNA. 3. The cyanobacteria were the first prokaryotic organisms t.

1. Give several pieces of evidence that RNA preceded proteins and DNA in living things. Do your
answers to (1) mean that the first life was RNA-based, with RNA serving as both the catalyst and
the genetic material? Briefly discuss the strengths and weaknesses of this hypothesis. It is
believed that the machinery for photosynthesis evolved only once, in the cyanobacteria.
However, several unrelated groups of eukaryotes, such as green plants, diatoms, and euglenoids,
are able to photosynthesize. How can this be explained? Answer each question True or False
(T/F). If the answer is false, explain why. Eukaryotic cells are more similar to archaea for genes
involved in protein synthesis and DNA replication, but more similar to bacteria for genes
involved in metabolism. RNA has been found in meteorites, and was produced in the Miller-
Urey experiment, giving evidence supporting the "RNA-first" hypothesis of the origin of life.
The last universal common ancestor of all living things lived less than 2 billion years ago. The
first living things required oxygen (O_2). The^12C/^13C ratio is higher in living things than in
atmospheric CO_2. Which of the following is your closest relative? Your second closest? a) a
fungus; b) a dinoflagellate; c) a pine tree; d) a choanoflagellate; e) a ciliate; f) an archaean Why
are marine organisms relatively common in the fossil record, but mountain-dwelling species
relatively rare?
Solution
1. RNA preceded proteins and DNA. This is strongly supported by the RNA World Hypothesis
proposed independetly by Carl Woese, Francis Crick and Leslie Orgel in 1960s. It says that the
ribosomes which are vital for protein formation are made up of RNA and the protein
arrangement task during traslation is actually carried by RNA thus confirming that the early
forms used RNA for their chemical reactions preceeding the use of proteins. Since RNA was
instable, eventually organisms started to depend on proteins and DNA for their activities.
2. The RNA theory states that the RNA was the earliest genetic material for the early forms of
life. This is due to the fact that RNA can act both as a genetic material and also as a catalyst
(enzyme). Because to carry out life processes the genes need to be produced. And this production
is dependent on enzymes inturn. A strong point that James Watson said is that RNA can translate
into DNA in the reverse transcription process, while doing so RNA itself could have acted as an
enzyme besides acting as a template to facilitate the reaction to carryout. This supports the
phrase 'Life requires autocatalysis'. The weaknesses of this hypothesis are it is highly
unpredictable to have RNA nucleotides with the requirement of any enzyme. Which means RNA
precursors cannot be formed without an enzyme. This conveys the message that there could have
been another simple molecule which has the catalytic property and information storge system
other than RNA.

2. 3. The cyanobacteria were the first prokaryotic organisms to use water molecule as their electron
source and fixed carbon dioxide to produce carbohydrates from light for their lives. This is
known as Photosynthesis. Later evolved eukaryotes which might have engulfed the cynobacteria,
thus becoming a permanent part of the eukaryotes leading to formation of chloroplast inside the
eukaryotes like diatoms, euglenoids and plants which are capable of performing photosynthesis.
Chloroplasts are considered as cyanobacteria and chloroplasts also have their own genetic
material. Hence is the saying 'prokaryote in a eukaryote'.
4. a. True b. True c. False, it lived 3.5 to 3.8 billions years ago d. False, they used some other
chemical, but oxygen was released as a poisonous gas e.False