One prominent theory on life origins was that RNA enzymes came into existence early inthe prebiotic history of Earth and were able to do basic chemical catalyses. Eventually,this “RNA-world” was overtaken by the stability of DNA as an information carrier and thediversity of catalytic functions capable of being performed by polypeptides. Is the RNA world hypothesis is a well-founded model?

One prominent theory on life origins was that RNA enzymes came into existence early inthe prebiotic history of Earth and were able to do basic chemical catalyses. Eventually,this “RNA-world” was overtaken by the stability of DNA as an information carrier and thediversity of catalytic functions capable of being performed by polypeptides. Is the RNA world hypothesis is a well-founded model?

BIOLOGY:CONCEPTS+APPL.(LOOSELEAF)

10th Edition

ISBN:9781305967359

Author:STARR

Publisher:STARR

Chapter18: Life's Origin And Early Evolution

Section: Chapter Questions

Problem 5SA: RNA in ribosome catalyzes formation of peptide bonds in all organisms. This supports the hypothesis...

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Antibiotics and Protein Synthesis Antibiotics are molecules produced by microorganisms as defense mechanisms. The most effective antibiotics work by interfering with essential biochemical or reproductive processes. Many antibiotics block or disrupt one or more stages in protein synthesis. Some of these are mentioned here. Tetracyclines are a family of chemically related compounds used to treat several types of bacterial infections. Tetracyclines interfere with the initiation of translation. The tetracycline molecule attaches to the small ribosomal subunit and prevents binding of the tRNA anticodon during initiation. Both eukaryotic and prokaryotic ribosomes are sensitive to the action of tetracycline, but this antibiotic cannot pass through the plasma membrane of eukaryotic cells. Because tetracycline can enter bacterial cells to inhibit protein synthesis, it will stop bacterial growth, helping the immune system fight the infection. Streptomycin is used in hospitals to treat serious bacterial infections. It binds to the small ribosomal subunit but does not prevent initiation or elongation; however, it does affect the efficiency of protein synthesis. Binding of streptomycin changes the way mRNA codons interact with the tRNA. As a result, incorrect amino acids are incorporated into the growing polypeptide chain, producing nonfunctional proteins. In addition, streptomycin causes the ribosome to randomly fall off the mRNA, preventing the synthesis of complete proteins. Puromycin is not used clinically but has played an important role in studying the mechanism of protein synthesis in the research laboratory. The puromycin molecule is the same size and shape as a tRNA/amino acid complex. When puromycin enters the ribosome, it can be incorporated into a growing polypeptide chain, stopping further synthesis because no peptide bond can be formed between puromycin and an amino acid, causing the shortened polypeptide to fall off the ribosome. Chloramphenicol was one of the first broadspectrum antibiotics introduced. Eukaryotic cells are resistant to its actions, and it was widely used to treat bacterial infections. However, its use is limited to external applications and serious infections. Chloramphenicol destroys cells in the bone marrow, the source of all blood cells. In bacteria, this antibiotic binds to the large ribosomal subunit and inhibits the formation of peptide bonds. Another antibiotic, erythromycin, also binds to the large ribosomal subunit and inhibits the movement of ribosomes along the mRNA. Almost every step of protein synthesis can be inhibited by one antibiotic or another. Work on designing new synthetic antibiotics to fight infections is based on our knowledge of how the nucleotide sequence of mRNA is converted into the amino acid sequence of a protein. Questions Why are antibiotics ineffective in treating the common cold and other virus infections?
Figure 29.15 highlights in red the DNA phosphate oxygen atoms. Some of them interact with catabolite activator protein (CAP). What kind of interactions do you suppose predominate, and what kinds of CAP amino acid side chains might be involved in these interactions?
Figure 15.16 Many antibiotics inhibit bacterial protein synthesis. For example, tetracycline blocks the A site on the bacterial ribosome, and chloramphenicol blocks peptidyl transfer. What specific effect would you expect each of these antibiotics to have on protein synthesis? Tetracycline would directly affect: tRNA binding to the ribosome ribosome assembly growth of the protein chain Chloramphenicol would directly affect tRNA binding to the ribosome ribosome assembly growth of the protein chain
In the gene-coding sequence shown here, which of the following events will produce a frameshift after the last mutational site? a. insertion of an A after the first codon b. deletion of the second codon (AAA) c. insertion of TA after the second codon and deletion of CG in the fourth codon d. deletion of AC in the third codon
Briefly describe the function of the following in protein synthesis. a. rRNA b. tRNA c. mRNA
If the coding region of a gene (the exons) contains 2,100 base pairs of DNA, would a missense mutation cause a protein to be shorter, longer, or the same length as the normal 700 amino acid proteins? What would be the effect of a nonsense mutation? A sense mutation?
Eukaryotic and prokaryotic ribosomes are similar in that: a. both contain a small subunit, but only eukaryotes contain a large subunit. b. both contain the same number of proteins. c. both use mRNA to assemble amino acids into proteins. d. both contain the same number of types of rRNA. e. both produce proteins that can pass through pores into the nucleus.
Energy that drives translation is provided mainly by ______ . a. ATP c. GTP b. amino acids d. ribosomes
Read the following experiment and interpret the results to form your conclusion. Experimental data: S bacteria were heat killed and cell extracts were isolated. The extracts contained cellular components, including lipids, proteins, DNA, and RNA. The extracts were mixed with live R bacteria and then injected together into mice along with various enzymes (proteases, RNAses, and DNAses). Proteases degrade proteins, RNAses degrade RNA, and DNAses degrade DNA. Based on these results, what is the transforming principle?
Eukaryotic mRNA: usessnRNPs to cut out introns and seal together translatableexons. uses a spliceosome mechanism made of DNA to recognizeconsensus sequences to cut and splice. has a guanine cap on its 39 end and a poly(A) tail on its 59 end. is composed of adenine, thymine, guanine, and cytosine. codes the guanine cap and poly(A) tail from the DNAtemplate.
Antibiotics and Protein Synthesis Antibiotics are molecules produced by microorganisms as defense mechanisms. The most effective antibiotics work by interfering with essential biochemical or reproductive processes. Many antibiotics block or disrupt one or more stages in protein synthesis. Some of these are mentioned here. Tetracyclines are a family of chemically related compounds used to treat several types of bacterial infections. Tetracyclines interfere with the initiation of translation. The tetracycline molecule attaches to the small ribosomal subunit and prevents binding of the tRNA anticodon during initiation. Both eukaryotic and prokaryotic ribosomes are sensitive to the action of tetracycline, but this antibiotic cannot pass through the plasma membrane of eukaryotic cells. Because tetracycline can enter bacterial cells to inhibit protein synthesis, it will stop bacterial growth, helping the immune system fight the infection. Streptomycin is used in hospitals to treat serious bacterial infections. It binds to the small ribosomal subunit but does not prevent initiation or elongation; however, it does affect the efficiency of protein synthesis. Binding of streptomycin changes the way mRNA codons interact with the tRNA. As a result, incorrect amino acids are incorporated into the growing polypeptide chain, producing nonfunctional proteins. In addition, streptomycin causes the ribosome to randomly fall off the mRNA, preventing the synthesis of complete proteins. Puromycin is not used clinically but has played an important role in studying the mechanism of protein synthesis in the research laboratory. The puromycin molecule is the same size and shape as a tRNA/amino acid complex. When puromycin enters the ribosome, it can be incorporated into a growing polypeptide chain, stopping further synthesis because no peptide bond can be formed between puromycin and an amino acid, causing the shortened polypeptide to fall off the ribosome. Chloramphenicol was one of the first broadspectrum antibiotics introduced. Eukaryotic cells are resistant to its actions, and it was widely used to treat bacterial infections. However, its use is limited to external applications and serious infections. Chloramphenicol destroys cells in the bone marrow, the source of all blood cells. In bacteria, this antibiotic binds to the large ribosomal subunit and inhibits the formation of peptide bonds. Another antibiotic, erythromycin, also binds to the large ribosomal subunit and inhibits the movement of ribosomes along the mRNA. Almost every step of protein synthesis can be inhibited by one antibiotic or another. Work on designing new synthetic antibiotics to fight infections is based on our knowledge of how the nucleotide sequence of mRNA is converted into the amino acid sequence of a protein. Questions Why is targeting protein synthesis an effective strategy for preventing infection?
Put the following processes in order of their occurrence during expression of a eukaryotic gene: a. mRNA processing c. transcription b. translation d. RNA leaves nucleus