Molec Cell assignments for test 1(0)-Word PAGE LAYOUT REFERENCES MAILINGS REVIEW

Question

Molec Cell assignments for test 1(0)-Word PAGE LAYOUT REFERENCES MAILINGS REVIEW VIE 2_.IA: A. Aa- :: . I-.. AaBbCcDel AaBbccor AaBbCt AaBbCct AaBI AaBbCct Font Paragraph Styles Assignment 3 (Organic) Evolution 1. Describe the RNA World theory. Identify two ways which make it plausible, and two ways in which the theory has problems. 2. Be capable of identifying at least two of the alternate theories, again, being able to specify two ways in which the theory is plausible and two ways in which it has problems.

Explanation / Answer

"RNA world theory proposes that life based on RNA pre-dates the current world life based on DNA (RNA molecule proliferates before the evolution of DNA and protein)." This concept of RNA world hypothesis was given by Alexander Rich(1962) and this term was coined by Walter Gilbert(1986). The two facts about RNA that it duplicate genetic information like DNA and its capability of acting like a ribozome made the scientists to believe that once it was capable of supportng independent life forms.

FEW THINGS ABOUT RNA:-

RNA can store information like protein.

RNA does several function in organisms (formation of protein etc).

DNA and Protein succeed RNA world.

some scientists believe that RNA has spontaneously on the earth.

A POSSIBLE RNA SCENARIO;-

production of short RNA molecule

replication of RNA molecule

synthesis of specific peptide

increasing role of peptide in RNA replication

primitive translation of peptide in RNA replication

genomic RNA copied into DNA

DNA genome translated on RNA protein complex

WHY IT IS PLAUSIBLE:-

1) This theory shows that RNA catalyze the formation of peptide bonds.

2) This theory confirms that RNA is a protein synthesizing machinery.

3)This theory was supported by the presence of RNA in viruses and absence of DNA in these viruses.

PROBLEMS OF THEORY:-

1) RNA is much more unstable than DNA (RNA is single stranded)

2) All the properties of RNA which are shown in this theory are also present in DNA and one more thing about DNA is that it does not have limitations which are present in RNA.

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