Launchpad Chapter 3 Exam

Which one of the following types of post-transcriptional modification is common in eukaryotes?

All of these choices are correct: polyadenylation, intron removal, 5' cap addition, polyadenylation and intron removal.

Which of the following is true of polycistronic RNA

- Translation of the mRNA may begin before transcription is finished. - It has multiple start codons and stop codons.

Imagine that your lab is synthesizing a new type of cell. One of your colleagues suggests that your synthetic cell should use prokaryotic systems for all the steps of gene expression (transcription and translation) because prokaryotic proteins synthesis is faster than eukaryotic protein synthesis. What characteristics of prokaryotic transcription and translation make the overall process faster than in eukaryotes?

- prokaryotes lack a nuclear envelope, so translation can begin on an mRNA even before transcription of the mRNA is complete - the primary transcript in prokaryotes does not undergo further processing, so translation can begin immediately - multiple proteins can be synthesized from a single, polycistronic mRNA molecule.

RNA makes up the genome of many different viruses, and it was probably the first information in evolutionary history. Yet, cells use DNA as the primary molecule for the storage of genetic information. What features of DNA make it a more suitable informational archive then RNA?

- the -H group on the 2' carbon of deoxyribose is less reactive than the -OH on the same carbon or ribose. - double-stranded DNA facilitates rapid and accurate replication of the information.

Using Chargaff's rules, you can determine that the DNA of an organism that contains 30% adenine would contain __________ guanine.

20%

Imagine you have discovered a new species of bacteria. To begin your investigation of this organism, you run an essay on the total nucleotide content of the bacterial cells. If the cytosine content od DNA from the bacterial cells is 17%, what is the adenine content?

33%

Which of the following is true of DNA?

A purine always forms a complementary base pair with a pyrimidine.

In which one of the following cellular processes is RNA involved?

All of the choices are correct: transcription, translation, DNA replication, transcription and translation.

Which of the following correctly indicates the complementary base pairing of adenine in DNA and RNA?

Adenine with thymine in DNA and with uracil in RNA

Non-virulent bacteria can be prevented from being transformed in to virulent bacteria of the debris from heat-killed virulent bacteria is first treated with:

DNase

Imagine that you and your colleagues are working in a lab to develop a protein synthesis system for a new type of synthetic cell. During your brainstorming sessions, you propose that polycistronic mRNA (an mRNA with multiple start and stop codons) would be much more useful than mRNA that is only translated into one protein (with just one start and stop codon). This would allow for multiple proteins necessary for a particular function to be translated together. One of your colleagues says that is a good idea, but if you decide to go with polycistronic mRNA, you'd better make sure to use a prokaryotic translation system. Why might it be problematic t use a eukaryotic translation system with polycistronic mRNA?

Eukaryotic ribosomes initiate translation by binding to the 5'-cap, which is only at one end of the mRNA.

Is the following statement about DNA and RNA true or false? Hydrogen bonds and phosphodiester bonds maintain the structure of DNA molecules, whereas only phosephodiester bonds are important for the structure of RNA molecules.

False

Is the following statement about DNA and RNA true or false? RNA is the primary long-term molecule for genetic information in eukaryotic cells.

False

Is the following statement about DNA and RNA true or false? The nitrogenous base thymine is present in DNA and RNA, while uracil is present only in RNA.

False

Is the following statement about DNA and RNA true or false? A hydrogen atom is present in the 3' carbon of the ribose of DNA nucleotides, whereas a hydroxyl group is present at the same position on RNA nucleotides.

False.

Is the following statement about DNA and RNA true or false? The DNA and RNA molecules in a cell are copied by replication before a cell divides.

False.

RNA polymerase can do which one of the following?

RNA polymerase is capable of all of these activities.

Which of the following correctly lists the components necessary for prokaryotic and eukaryotic transcription?

RNA polymerase, general transcription factors, DNA, and RNA nucleotides.

An intron is ...

RNA that is removed during the processing of an RNA molecule and remains inside the nucleus.

Is the following statement about DNA and RNA true or false? DNA is a double-stranded molecule, and RNA is single-stranded.

True

Which one of the following nucleotides hydrogen base pairs with adenine in an RNA molecule?

Uracil

Alternative splicing allows for:

different polypeptides to be made from a single gene.

An exon is .....

part of an intact, mature mRNA that leaves the nucleus.

In the spiral staircase analogy if DNA structure, each railing represents a __________________.

sugar-phosphate backbone, and each step represents a pair of nitrogenous bases.

You are investigating an abnormal eukaryotic cell line that makes all of its mRNA much longer than the mRNAs from normal cells (that is, they have more nucleotides than usual). Intrigued you examine the protein in these abnormal cells and note that many of them are either much longer or much shorter than the normal proteins from nonmutant cells. Assuming there is just one mutant defect in these cells, what is that defect?

the spliceosome is nofunctional

In order to test the effects of a new drug, you isolate the messenger RNA molecules from both treated and untreated eukaryotic cells and separate them according to size using gel electrophoresis. In each lane of the gel, the shorter RNA molecules migrate more quickly through the gel and end up near the bottom of the gel while the longer RNAa migrate more slowly and remain near the top.

these results suggest that the drug affects RNA processing