Ch 17 Quiz

11. Discuss how can human cells make 75,000- 100,000 different proteins given that there are about 20,000 human genes?

Alternative splicing of exons will cause different mRNAs. This causes the making of many different proteins.

12. Discuss TWO mechanisms or process that ensure the correct amino acid is added to the growing polypeptide chain.

Aminoacyl-tRNA synthetases uses a secondary genetic code to load the correct amino acid to each tRNA. A second mechanism is the pairing of the tRNA anticodon with the appropriate mRNA codon.

When the genetic material was first being isolated and studied, there was a controversy about it being protein or DNA (as discussed in Chapter 16). Those that backed protein as the genetic material almost got it right. Discuss what the connection was between the two molecules that was missed.

DNA has the code, or instructions, to synthesize proteins.

14. Discuss why the definition of "what is a gene" has recently been expanded to non-protein molecules.

Most euroyic genes contsin noncoding segmtne such as introns. Molecular biologists also include promoters and certain other regulatory region of DNA within the boundaries of genes. The statement that a gene codes for a polypeptide is too simple.

9. Contrast and compare the following mutations in terms of the genetic code:

Nonsense mutation is when a changed codon becomes a stop codon. Sense mutation is when the stop codon changes to a reading codon. Missense mutation is when altered codons still code for AA's, but not the right ones.

Discuss THREE ways that the mRNA used in protein synthesis differs from the original RNA transcript. What is the apparent function of each of the alterations or modifications?

Poly a tail and 5' cap are formed. They share several important functions, such as facilitating the export of the mRNA from the nucleus. They help protect the mRNA from degradation by hydrolytic enzymes. RNA splicing also occurs, which is responsible for removing introns, and exons are joined together.

Describe how the genotype of an organism is turned into the phenotype.

Protein are the link between genotype and phenotype. Genes dictate phenotypes through enzymes.

10. Compare DNA polymerase and RNA polymerase in terms of how they function, the requirement for a template and primer, the direction of synthesis and the type of nucleotides used.

RNA polymerase are enzymes for building RNA from RNA nucleotides. DNA polymerase synthesizes DNA molecules. Like DNA polymerase, RNA polymerases can assemble in the 5'---3' direction. Unlike DNA polymerases, RNA polymerases are able to start a chain from scratch.They do not need to add the first nucleotide onto a pre-existing primer. RNA uses Uracil, and DNA uses Thymine.

13. Suppose that a burst of X-rays have caused a sequence change in the TATA box of a particular gene. Speculate on what affect this might this on the transcription and translation of the gene?

The transcription factor would not be able to bind because it is unable to recognize the TATA sequence change. RNA polymerase would also not bind causing transcription to not occur.

Describe a mechanism used to route the production of a protein for exportation out of a cell.

They are moved in transport vesicles that move through the cytoplasm and fuse with the plasma membrane releasing the protein out of the cell. Ribosomes attached to the Rough ER function in synthesizing proteins that will be moved out of the cell. The polypeptides of proteins destined for the endomembrane system or for secretion are marked by a signal peptide, which targets the protein to the ER.

Another Eli Lilly candidate drug impairs the function of the large unit of the prokaryotic ribosome. Discuss if this drug would have any potential use in controlling bacterial diseases and if it would be expected to be dangerous to humans.

This drug would have potential use in controlling bacterial diseases because if it impairs the function of the large unit of a ribosome, then proteins would not be made. Certain antibiotics can inactivate a bacterial ribosome without inhibiting the ability of eukaryotic ribosomes to make proteins.

The enantiomer form of a candidate drug from Eli Lilly Co. was found to cause deletions of one base pair at various intervals in the DNA of test animals. Explain to the stockholders why the drug should or should not be put into commercial production (details at the molecular level are important in your answer).

This would cause a frameshift mutation. All nucleotides downstream of the deletion will be improperly grouped into codons. Unless the frameshift is very near the end of the gene, the protein will be nonfunctional.

A new candidate drug produced by Eli Lilly damages a transcription factor molecule. Describe the probable outcome of this damage and speculate on what results it might have on the organism.

Transcription factors mediate the binding of RNA polymerase and initiation of transcription, so there would be problems with the binding of RNA polymerase and transcription.