MCB Exam 2

What is the difference between conserved and consensus?

--Being conserved indicates that the one thing being investigated is similar in many different places --Being a consensus indicates this is specifically what you will find at that protein.

F all 5 nucleotides could be used equally to create nucleic acid, how many possible trinucleotides are there? Enter your answer as a whole number, not text or an equation.

125

What is/are a net result of glycolysis for every molecule of glucose?

2 ATP, 2 NADH, 2 Pyruvates

Which of the following were determined specifically by Franklin & Wilkins in their x-ray diffraction studies? Choose all that apply, and remember that just because a statement is accurate does not necessarily make it a correct response to the question posed. 1. The ratio of A to T in a given organism's DNA is 1. 2. DNA has a uniform width down the length of the molecule. 3. DNA is an antiparallel molecule. 4. The sugars and phosphates in a DNA molecule are on the outside. 5. GC base pairs have 3 H-bonds; AT base pairs have 2 H-bonds.

2. DNA has a uniform width down the length of the molecule. 4. The sugars and phosphates in a DNA molecule are on the outside.

What is the approximate pH of the mitochondrial intermembrane space?

7; same as cytoplasm

You are studying a ribosome, and isolate an RNA molecule that has a Svedberg value of 18S. Which of the following statements would you be confident making? Choose all that apply. A. This RNA is from a small ribosomal subunit. B. This RNA would be part of a 70S ribosome. C. This RNA was the only RNA in the subunit from which it was taken. D. This RNA is from a bacterial cell.

A. This RNA is from a small ribosomal subunit. C. This RNA was the only RNA in the subunit from which it was taken.

Alternative splicing allows for: A. a larger proteome relative to the genome. B. a 1:1 relationship between genome and proteome. C. a larger genome relative to the proteome. D. different genes to be assembled into a single protein.

A. a larger proteome relative to the genome.

The following figure is of three pieces of DNA from different organisms. Black indicates coding regions of DNA; White indicates intergenic DNA; Gray indicates intervening sequences of DNA. https://d1py7umku9kunm.cloudfront.net/assets/1729169/Genedensity.jpg Order the pieces of DNA from lowest gene density to highest gene density

A<C<B

What is the significance of the -10 and -35 sites in bacterial promoters?

Bacterial RNA polymerase is made a single way, and is built to recognize something very specific

Can you summarize the difference between DNA replication and transcription?

Similarities: both involve recognizing a start signal of specific bases, separating the DNA at/hear that point, and reading a template molecule from 3'-5' in order to be synthesizing nucleic acid 5'-3' Differences: --DNA rep. copies both stranded, every base included --transcription is individual genes, and one strand or the other is the template --rep. makes SNA, trans. makes RNA

Which option(s) describe(s) DNA at its temperature of melting (Tm)?

The point at which each DNA molecule is 50% single stranded and 50% double stranded. https://d1py7umku9kunm.cloudfront.net/assets/282628/temp-3.jpg

Which one of the following best describes the relationship between sister chromatids? They are single-stranded molecules complementary to each other. They are similar double helical molecules, but not identical since one came from the mother and the other from the father. They are identical double helical molecules attached to each other. There are no sequence relationships between them, but they are approximately the same size and therefore linked to each other.

They are identical double helical molecules attached to each other.

Suppose that a portion of double-stranded DNA in the middle of a large gene is being transcribed by an RNA polymerase. As the polymerase moves through the sequence of six bases shown in the diagram below, what is the corresponding sequence of bases in the RNA that is produced? Diagram of DNA showing a coding strand and a template strand. Coding strand from the 3 prime end to the 5 prime end reads C C G A G T. Template strand from the 5 prime end to the 3 prime end reads G G C T C A. Enter the sequence of bases as capital letters with no spaces and no punctuation. Begin with the first base added to the growing RNA strand, and end with the last base added.

UGAGCC

The figure below shows a moment during the process of transcription, and the gray shaded oval represents a template-directed nucleic acid synthesizing enzyme: https://d1py7umku9kunm.cloudfront.net/assets/3681251/ex_02_sp16_promoter.jpg The molecule represented by the gray shaded oval moves in the direction towards _______, reading _______ as a template. (X); (A) (X); (B) (Y); (A) (Y); (B)

Y B

Which of the following statements about chromatin organization is/are correct? Choose all that apply. a. Although the amino acids in a histone tail do not adopt appreciable secondary structure, those amino acids play an important role in regulation of chromatin accessibility. b. Linker DNA between core nucleosomes can be degraded without disrupting the structure of the core nucleosome itself. c. Two amino acids that appear in unusually high percentages in histone proteins are aspartic acid and glutamic acid, reflecting their role in interacting with DNA. d. Histones are evolutionarily ancient molecules, as evidenced by their conserved sequences in all three domains.

a, b

Taking into account the wobble hypothesis, which of the following mRNA sequences could be bound to the tRNA anticodon 3' GGC 5'? a. 5′ CCA 3′ b. 3′ UGC 5′ c. 5′ UGC 3′ d. 3′ CCG 5′

a. 5′ CCA 3′ Codons are written in the 5′ to 3′ direction. Their corresponding mRNA sequences are 5′ to 3′. This codon could bind to the proline anticodon shown, because it also codes for proline.

Each codon shown below specifies an amino acid. For which one is it possible that a change in a single base could create a stop codon? a. AAA b. CAC c. ACA d. ACC

a. AAA Changing the first base from A—>U creates the stop codon UAA.

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication? a. Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication. b. DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semi-conservative. c. DNA polymerases of prokaryotes can add nucleotides to both 3' and 5' ends of DNA strands, while those of eukaryotes function only in the 5' → 3' direction. d. Prokaryotic replication does not require a primer.

a. Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

What type of bonding is responsible for maintaining the shape of the tRNA molecule? a. hydrogen bonding between base pairs b. van der Waals interactions between hydrogen atoms c. peptide bonding between amino acids d. covalent bonding between sulfur atoms e. ionic bonding between phosphates

a. hydrogen bonding between base pairs

Shine-Delgarno sequences are present in mRNAs of a. prokaryotes. b. eukaryotes. c. fungi. d. algae. e. mosses.

a. prokaryotes.

To label amino acids within cells, researchers "pulsed" E. coli with radioactive sulfate and "chased" with a large excess of nonradioactive sulfate. They observed that radioactivity was first associated with ribosomes and then later with completed proteins. The biologists concluded that _____. a. proteins are synthesized by ribosomes and are subsequently released b. ribosomes break down proteins into amino acids c. amino acids are randomly assembled into proteins d. polypeptides are made in the nucleus

a. proteins are synthesized by ribosomes and are subsequently released Translation of mRNA to protein occurs within the cytoplasm of a eukaryotic cell.

If there were a mutation in a ribosome that prevented tRNA molecules from moving into the E site, how many amino acids would be found in the resulting peptide chain formed on this ribosome? a. A minimum of two b. A maximum of two c. A maximum of one d. None

b. A maximum of two

After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? a. Coding sequences called exons are spliced out by ribosomes. b. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. c. A translation stop codon is added at the 3' end of the pre-mRNA. d. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. e. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.

b. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. d. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. e. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.

How did the A site of the ribosome get its name? a. In this site the tRNA no longer has an amino acid attached and is about to exit the ribosome. b. It is the site occupied by incoming aminoacyl tRNAs. c. It is where amino acids are joined to tRNAs, producing aminoacyl tRNAs. d. It is where the polypeptide chain attached to the tRNA is transferred to the aminoacyl tRNA for peptide-bond formation.

b. It is the site occupied by incoming aminoacyl tRNAs.

Which is the best description of the loops in a tRNA molecule? a. Regions created as the result of hydrogen bonding between base pairs b. Regions of the molecules that remain as single-stranded RNA due to the absence of complementary base pairs c. Regions provided for binding to the mRNA codon d. Single-stranded DNA bases

b. Regions of the molecules that remain as single-stranded RNA due to the absence of complementary base pairs The noncomplementary base pairs do not bind to each other and thus result in the formation of loops.

Which of the following is true of the sequence called the TATA box? Which of the following is true of the sequence called the TATA box? a. The sequence is located 30 base pairs upstream of the transcription site and is recognized by sigma factor. b. The sequence is located 30 base pairs upstream of the transcription site and is important for recognition by RNA polymerase. c.The sequence is required for proper polyadenylation of the mRNA. d. The sequence is located 30 base pairs downstream of the transcription site and is important for recognition by RNA polymerase.

b. The sequence is located 30 base pairs upstream of the transcription site and is important for recognition by RNA polymerase.

Which of the following enzymes when added to a spliceosome is predicted to prevent recognition of pre-mRNA regions critical for splicing? Which of the following enzymes when added to a spliceosome is predicted to prevent recognition of pre-mRNA regions critical for splicing? a. a protease specific for a release factor b. an RNase specific for snRNAs c. an RNase specific for tRNAs d. a protease specific for initiation factors

b. an RNase specific for snRNAs

Where is the start codon located? a.at the downstream end of the 3' untranslated region (UTR) b. at the downstream end of the 5' untranslated region (UTR) c. at the upstream end of the 3' untranslated region (UTR) d. at the very start (5' end) of the mRNA

b. at the downstream end of the 5' untranslated region (UTR)

What is recognized by an aminoacyl tRNA synthetase? a. the nucleotides needed to synthesize a tRNA b. one amino acid and the set of tRNAs that are coupled to that amino acid c. the set of redundant codons that specify one amino acid d. one specific codon

b. one amino acid and the set of tRNAs that are coupled to that amino acid

Telomerase is needed to ______. a. allow DNA replication at the ends of chromosomes to occur in the 3' to 5' direction b. prevent the loss of DNA bases at the ends of linear chromosomes c. create repetitive DNA sequences that allow the assembly of the kinetochore d. open the two strands of DNA in front of the replication fork e. synthesize telomere proteins

b. prevent the loss of DNA bases at the ends of linear chromosomes

If you were designing a method to specifically inhibit prokaryotic transcription, but not eukaryotic transcription, interfering with which of the following would work best? If you were designing a method to specifically inhibit prokaryotic transcription, but not eukaryotic transcription, interfering with which of the following would work best? a. an intercalating agent b. recognition of the promoter region c. DNase activity RNA polymerase II activity d. ribosomal binding

b. recognition of the promoter region

What molecules in the spliceosome catalyze the intron removal reactions? What molecules in the spliceosome catalyze the intron removal reactions? a. tRNA b. ribozymes c. RNA polymerases d. introns

b. ribozymes

How is a mature mRNA that lacks introns produced in eukaryotic cells? a. A 5′ cap is added to the primary RNA transcript, removing introns. b. snRNPs bind to the primary transcript and form the spliceosome, which removes introns. c. A ribosome binds to the primary transcript and modifies it, removing introns. d. A poly (A) tail is added to the primary RNA transcript, removing introns.

b. snRNPs bind to the primary transcript and form the spliceosome, which removes introns. The binding of snRNPs is the first step toward formation of the spliceosome, which is a protein complex that splices introns out of the primary RNA transcript to form mRNA.

When an amino acid is specified by more than one codon, what is usually shared by the set of codons that specify this amino acid? a. their entire base sequence b. the first and second bases c. the second base d. the first base e. the third base

b. the first and second bases

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare? a. The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes. b. Prokaryotic codons usually contain different bases than those of eukaryotes. c. Codons are a nearly universal language among all organisms. d. Prokaryotic codons usually specify different amino acids than those of eukaryotes.

c. Codons are a nearly universal language among all organisms.

As scientists were unraveling the mysteries associated with transcription and translation in eukaryotes, they discovered there was not a one-to-one correspondence between the nucleotide sequence of a gene and the base sequence of the mRNA it codes for. They proposed the genes-in-pieces hypothesis. How can the genes-in-pieces hypothesis be explained? As scientists were unraveling the mysteries associated with transcription and translation in eukaryotes, they discovered there was not a one-to-one correspondence between the nucleotide sequence of a gene and the base sequence of the mRNA it codes for. They proposed the genes-in-pieces hypothesis. How can the genes-in-pieces hypothesis be explained? a. Exons are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing. b. Exons are noncoding segments of DNA that are not read or transcribed by RNA polymerase II. c. Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing. d. Introns are noncoding segments of DNA that are not read or transcribed by RNA polymerase II.

c. Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.

What is the significance of the 2' hydroxyl on ribose for RNA function compared to DNA which lacks the 2'? a. The 2' hydroxyl prevents RNA from forming complementary base pairs. b. The 2' OH prevents RNA from storing information. c. The 2' OH increases the reactivity of RNA. d. The 2' OH increases the hydrophobicity of RNA.

c. The 2' OH increases the reactivity of RNA. The hydroxyl group is reactive and can help RNA to function as a ribozyme. The lack of a 2' OH in DNA increases the stability of the genetic material.

How does the bacterial ribosome recognize where to start translation? a. The small ribosomal subunit binds to the 5' cap of the mRNA. b. The small ribosomal subunit binds to the 3' poly(A) tail of the mRNA. c. The small ribosomal subunit binds to a sequence in the mRNA just upstream of the start codon. d. The small ribosomal subunit binds to the start codon.

c. The small ribosomal subunit binds to a sequence in the mRNA just upstream of the start codon.

https://session.masteringbiology.com/problemAsset/1739861/1/0338.jpg Refer to the figure above. The mRNA is smaller than the length of the DNA that codes for it because _____. Refer to the figure above. The mRNA is smaller than the length of the DNA that codes for it because _____. a. bases are added to the tail of the primary transcript b. post-transcriptional modification removes the exons c. post-transcriptional modification removes the introns d. the regulatory regions (exons) of the gene are not transcribed

c. post-transcriptional modification removes the introns

5' caps and 3' poly(A) tails of eukaryotic mRNAs ______. a. protect mRNA from degradation and enhance transcription b. mark the beginning and end of introns, respectively c. protect mRNA from degradation and enhance translation d. act as sites for the start and stop of translation, respectively

c. protect mRNA from degradation and enhance translation

During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand? For any given gene, what ultimately determines which DNA strand serves as the template strand? a.the location of specific proteins (transcription factors) that bind to the DNA b. which of the two strands of DNA carries the RNA primer c. the base sequence of the gene's promoter d. the location along the chromosome where the double-stranded DNA unwinds

c. the base sequence of the gene's promoter

What would occur if a mutation caused an aminoacyl-tRNA synthetase to recognize both its normal amino acid and a different one? a. Translation would occur normally. b. All codons would be misread. c. One or more codons would always be misread. d. One or more codons would sometimes be misread.

d. One or more codons would sometimes be misread.

Transcription normally stops when the _____. Transcription normally stops when the _____. a. RNA polymerase reaches a stop codon on the mRNA b. RNA polymerase is denatured c. mRNA reaches a specific length and detaches from the DNA molecule d. RNA polymerase reaches a termination signal on the DNA that leads to the formation of a hairpin loop in the mRNA

d. RNA polymerase reaches a termination signal on the DNA that leads to the formation of a hairpin loop in the mRNA

Use this model of a eukaryotic transcript to answer the following question. E = exon and I = intron 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to the transcript shown above, it can attach _____. Use this model of a eukaryotic transcript to answer the following question. E = exon and I = intron 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to the transcript shown above, it can attach _____. a. to the 5' UTR b. to the eons c. to the 3' UTR d. at certain sites along an intron

d. at certain sites along an intron

Ribosomes are very old structures, found in all organisms. As a result, molecular taxonomists are looking at relationships based upon which rRNA sequence(s)? a. 16S b. 18S c. 30S d. both choices A and B e. all of the above

d. both choices A and B

In eukaryotes, when mature mRNA is hybridized to complementary DNA, ______. a. exons loop out as single-stranded regions of DNA b. exons loop out as single-stranded regions of RNA c. introns loop out as single-stranded regions of RNA d. introns loop out as single-stranded regions of DNA

d. introns loop out as single-stranded regions of DNA These regions are transcribed but are removed from the RNA by splicing.

The wobble hypothesis explains ______. a. the fact that there are three nucleotides per codon b. the redundancy of the genetic code c. the imprecise fit between aminoacyl tRNA synthetases and their substrates d. the ability of some tRNAs to read more than one codon

d. the ability of some tRNAs to read more than one codon

Which of the following is the first event to take place in translation in eukaryotes? a. elongation of the polypeptide b. base pairing of activated methionine-tRNA to AUG of the messenger RNA c. covalent bonding between the first two amino acids d. the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA e. binding of the larger ribosomal subunit to smaller ribosomal subunits

d. the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

One reason that prokaryotic genes do not contain introns is that a. the introns are cut out during binary fission. b. due to the short time the bacterium is around as a single organism, a 5' cap and poly (A) tail are added immediately for translation to take place. c. bacterial proteins are very short and not subject to mutation. d. translation sometimes begins before transcription has been completed because prokaryotes do not have a nucleus. e. integrated viral DNA is not recognized for transcription.

d. translation sometimes begins before transcription has been completed because prokaryotes do not have a nucleus.

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base? a. Radioactive thymine would pair with nonradioactive guanine. b. Neither of the two daughter cells would be radioactive. c. One of the daughter cells, but not the other, would have radioactive DNA. d. All four bases of the DNA would be radioactive. e. DNA in both daughter cells would be radioactive.

e. DNA in both daughter cells would be radioactive.

Which one of the following statements about euchromatin is incorrect? a. It is most frequently found in the form of 30nm fibers. b. It is less densely packed than heterochromatin. c. It gets condensed during M-phase. d. It is more difficult to see under the electron microscope than heterochromatin. e. It is typically found at the periphery of the nucleus.

e. It is typically found at the periphery of the nucleus.

The redundancy of the genetic code is a consequence of ______. a. having three-letter-long genetic words (codons) b. having an equal number of codons and amino acids c. having fewer codons than there are amino acids d. having four different letters (As, Cs, Gs, and Us) in the genetic alphabet e. having more codons than amino acids

e. having more codons than amino acids

The environment between the outer and inner nuclear membranes is most accurately referred to as the: a. nuclear envelope. b. nucleoplasm. c. intermembrane space. d. cytoplasm. e. perinuclear space.

e. perinuclear space.

In which of the following compartments does mRNA processing (intron removal, cap addition, tail addition) typically occur in bacteria? Choose all that apply. The nucleus The cytoplasm

neither; bacteria do not typically do these things to their mRNA while eukaryotes do

Where does RNA processing occur

nucleus in eukaryotes