Genetic Information and Protein Synthesis

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Questions and Answers

What percentage of DNA is converted into proteins?

10%

50%

20%

5% (correct)

What happens if DNA is damaged?

Only proteins are affected

Nothing happens

Only some mRNAs are affected

All mRNAs and proteins are affected (correct)

How many copies of DNA are present in diploid cells?

2 (correct)

What is the approximate percentage of DNA that is transcribed into RNA?

80% Signup and view all the answers

What is the relationship between the number of molecules and the flow of genetic information?

The number of molecules increases as genetic information flows Signup and view all the answers

Why is it essential to copy DNA with high fidelity?

So that the sequence of DNA is preserved Signup and view all the answers

What is the main reason why the error in RNA molecules is less important than in DNA?

Because RNA molecules have multiple copies, and an error in one copy does not affect the others Signup and view all the answers

Why is the repair of DNA more important than the repair of RNA and proteins?

Because DNA contains the genetic information and has only one copy Signup and view all the answers

What is the main reason why the error rate is higher in translation than in replication?

Because the fidelity of translation is lower than that of replication Signup and view all the answers

Why is there a balance between the effort to maintain fidelity and the cost of energy expenditure?

Because the cell needs to balance the cost of maintaining fidelity with the energy expenditure Signup and view all the answers

What is the main function of the control mechanisms in DNA replication, transcription, and translation?

To ensure the accuracy of the genetic information Signup and view all the answers

What is the consequence of the error in protein structure compared to error in sequence?

Error in protein structure is more important to solve than error in sequence Signup and view all the answers

What is the main purpose of the kinetic discrimination mechanism?

To ensure the correct pairing of nucleotides with the template Signup and view all the answers

What is the error rate of the kinetic discrimination mechanism?

10-6 Signup and view all the answers

What is the purpose of the proofreading mechanism?

To reduce the error rate of DNA replication Signup and view all the answers

Which type of DNA polymerase does not have proofreading activity?

Taq polymerase Signup and view all the answers

What is the combined error rate of the kinetic discrimination and proofreading mechanisms?

10-8 Signup and view all the answers

What is the result of using the proofreading mechanism?

Decreased error rate of DNA replication Signup and view all the answers

What is the purpose of post-replicative repair mechanisms?

To decrease the error rate of DNA replication Signup and view all the answers

What is the final fidelity of DNA replication after all mechanisms are taken into account?

10-9 Signup and view all the answers

Study Notes

Central Dogma in Numbers

Genetic information is presented in DNA, transcribed into RNA, and ends in proteins.
DNA accounts for 100% of genetic information, but only about 80% is transcribed into RNA, and only about 5% of that is converted into proteins.
The amount of genetic information decreases from DNA to metabolites, but the number of molecules increases exponentially.
There is a single copy of DNA per cell (two if diploid), but multiple copies of RNA and proteins, with varying concentrations that can establish the phenotype of the organism.

Error Rates and Fidelity

The error rate is lowest in replication and highest in translation, with a higher fidelity in DNA synthesis compared to mRNA or protein synthesis.
The pressure to correct errors decreases as you move from DNA to metabolites, with repair being more important in DNA and degradation being more practical in RNA and proteins.
The error rate in DNA replication is critical, as all subsequent mRNA and protein molecules will be affected.

Stability and Degradation

DNA is extremely stable and does not degrade, except in apoptosis.
mRNA and proteins are unstable and have short half-lives, making errors in these molecules transient and eventually disappearing.
The instability of mRNA and proteins reduces the need for correction and allows for degradation of faulty molecules.

Control of Fidelity and Energy Cost

Maintaining fidelity requires a balance between the energy expended to correct errors and the energy cost of doing so.
The cost of maintaining fidelity includes factors such as transcriptional noise, biological noise, and the energy required to eliminate errors.
The trade-off between fidelity and energy cost affects the speed of copying, the number of genes involved, and the overall expression of genetic information.

Mechanism of Proofreading in DNA Pol

DNA polymerase has a high fidelity due to two mechanisms: kinetic discrimination and proofreading.
Kinetic discrimination involves the correct pairing of nucleotides with the template, ensuring a stable bond.
Proofreading involves a second active center that checks the correctness of the bond, requiring the DNA polymerase to have a 3'→5' exonuclease activity.
The combination of these two mechanisms results in a very low error rate of 10^-7 to 10^-8.
The use of proofreading reduces the error rate but slows down the process and increases the energy cost and number of genes required.

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Description

Test your understanding of how genetic information is stored in DNA, transcribed into RNA, and ultimately translated into proteins. Learn about the percentage of DNA that is transcribed and the role of enzymes in metabolite production.