Annotation of the human genome sequence reveals a discrepancy bet...

Question

Annotation of the human genome sequence reveals a discrepancy between the number of protein-coding genes and the number of predicted proteins actually expressed by the genome. Proteomic analysis indicates that human cells are capable of synthesizing more than 100,000 different proteins and perhaps three times this number. What is the discrepancy, and how can it be reconciled?

Accepted Answer

Hi everyone. Let's look at our next problem. It says the number of predicted proteins is generally much higher than the number of genes because of and our answer choices are a alternative splicing B five prime capping, see DNA synthesis or D elongation. And the answer we're looking for here is choice a alternative splicing. That's the alternative arrangements different arrangements of in tron Exxon spicing when making the mature M. R. N. A. And that means that multiple proteins Can be generated from a single gene. One gene spliced. One way you produce one protein spliced differently. You produce a different kind of protein and so forth. And in fact from the human proteome map they sequence or they generate a show about 20, protein coding genes And in that podium map they identify over 290,000 different peptides produced by those 20, protein coding genes. So as our question says, number of proteins much higher than the number of genes. Let's look at our other answer choices to understand why they're not correct choice B five prime capping is just the addition of alternate form of guanine on the five prime end of the M. RNA molecule. Um And that's just a protective function for the M. RNA, preventing it from degrading the presence of that cap. But it doesn't have to do with how many genes or how many proteins are generated from a gene. So that's not a correct choice choice C. D. N. A synthesis. Um This doesn't DNA synthesis is just the generating of duplicate DNA molecules. Force cell reproduction. So as cells divide, you have to copy the DNA for the new cell. Um But it's just replicating the genes that are they're not generating protein. So that's why choice C. Is incorrect. And then finally to D elongation, an elongation is just that process in D. N. A. Or RNA synthesis where the strand is getting, the new strand is getting longer. So just the synthesis of a poly nucleotide strand. But again it's a part of DNA synthesis which is not why we have um a much higher number of proteins than the number of genes. So that's why that's not a correct answer. So we'll cross that off and again, the number of predicted proteins is generally much higher than the number of genes. Because of choice. A alternative splicing. See you in the next video.

Key Concepts

Gene Expression and Alternative Splicing

Post-Translational Modifications

Proteomics and Protein Diversity

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