What kind of data is available on which to base the origin of life theory and the Panspermia theory?
6 answers
Which origin of life theory?
The origin of life on Earth.
The origin of life (abiogenesis) is not understood anywhere near as well as evolution is, so no one can give you a really strong answer.
There are several different theories for the OOL, one of which is the RNA World theory. Originally, it held that a specific type of RNA (a self-replicating RNA molecule, which would be called an RNA replicase ribozyme) was the first living entity, but some newer versions of the RNA World hold instead that life arose before the RNA World (a simpler self-replicator that was the first living entity, and then that gave rise to the RNA World).
There are several different theories for the OOL, one of which is the RNA World theory. Originally, it held that a specific type of RNA (a self-replicating RNA molecule, which would be called an RNA replicase ribozyme) was the first living entity, but some newer versions of the RNA World hold instead that life arose before the RNA World (a simpler self-replicator that was the first living entity, and then that gave rise to the RNA World).
Some biochemical evidences that there was once an RNA World...
1. The RNA World solves the chicken-or-egg paradox, “Which came first, DNA or proteins?” The answer would be, neither: an RNA molecule capable of both storing genetic information and catalyzing its own replication would have come first.
2. The peptidyl transferase activity of a ribosome is performed by RNA in the ribosome, not by a protein component
3. RNA primers are required by all DNA polymerases (indicates that RNA predates DNA).
4. DNA nucleotides are made from RNA nucleotides: cells start with an RNA nucleotide, then convert it into a DNA nucleotide (again, indicates that RNA predates DNA).
5. RNA nucleotides are used in several other fundamental biochemical processes
a. ATP
b. Coenzyme A and its derivative acetyl-CoA
c. NAD+, NADP+, and FAD+
1. The RNA World solves the chicken-or-egg paradox, “Which came first, DNA or proteins?” The answer would be, neither: an RNA molecule capable of both storing genetic information and catalyzing its own replication would have come first.
2. The peptidyl transferase activity of a ribosome is performed by RNA in the ribosome, not by a protein component
3. RNA primers are required by all DNA polymerases (indicates that RNA predates DNA).
4. DNA nucleotides are made from RNA nucleotides: cells start with an RNA nucleotide, then convert it into a DNA nucleotide (again, indicates that RNA predates DNA).
5. RNA nucleotides are used in several other fundamental biochemical processes
a. ATP
b. Coenzyme A and its derivative acetyl-CoA
c. NAD+, NADP+, and FAD+
Abiotically (that is, non-biologically) produced organic compounds important for RNA World
1. Purines (xanthine, hypoxanthine, guanine, and adenine) were present in the Murchison meteorite
2. The pyrimidine uracil was present in the Murchison meteorite
3. The pyrimidines cytosine and uracil can be produced abiotically
4. 70 different amino acids were found in Murchison meteorite (genetically encoded proteins would not be part of the RNA World, but nothing rules out very short peptides, which could arise by chance, from playing a role in the RNA World: in fact, single amino acids and dipeptides have been found to catalyze certain chemical reactions).
1. Purines (xanthine, hypoxanthine, guanine, and adenine) were present in the Murchison meteorite
2. The pyrimidine uracil was present in the Murchison meteorite
3. The pyrimidines cytosine and uracil can be produced abiotically
4. 70 different amino acids were found in Murchison meteorite (genetically encoded proteins would not be part of the RNA World, but nothing rules out very short peptides, which could arise by chance, from playing a role in the RNA World: in fact, single amino acids and dipeptides have been found to catalyze certain chemical reactions).
And here are some important experiments that relate to the RNA World (to differing degrees).
1. RNA 20-50 mers were produced using a 10 mer primer on montmorillonite
2. Multiple classes of ribozyme ligases were isolated from a pool of 10^15 **RANDOM** 220 mers
3. Scientists ‘evolved’ one of the above-mentioned ribozyme ligases into a high-fidelity, generalized RNA polymerase
4. Two different ribozyme ligases have been found capable of undergoing continuous evolution
1. RNA 20-50 mers were produced using a 10 mer primer on montmorillonite
2. Multiple classes of ribozyme ligases were isolated from a pool of 10^15 **RANDOM** 220 mers
3. Scientists ‘evolved’ one of the above-mentioned ribozyme ligases into a high-fidelity, generalized RNA polymerase
4. Two different ribozyme ligases have been found capable of undergoing continuous evolution
3 answers