BIO 101 Exam 4 (CH.16-17)

Which of the following statements about ribozymes is/are correct?(select all that apply)

In some genes, intron RNA functions as a ribozyme and catalyzes its own excision; Ribozymes are RNA molecules that function as enzymes; A ribosome can be regarded as one large ribozyme

Which answer best describes the role of telomerase in replicating the ends of linear chromosomes?

It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity

Which of the following statements correctly describes the function of a signal peptide?

It helps target a protein to the ER

Which of the following statements describes the effect of a nonsense mutation on a gene?

It introduces a premature stop codon into the mRNA

Which of the following statements accurately describes the structure of a eukaryotic chromosome?

It is a single linear molecule of double-stranded DNA plus proteins

Which of the following statements correctly describes a ribozyme?

It is an RNA with catalytic activity

Which of the following statements about the function of RNA polymerase is correct?

It unwinds the double helix and adds nucleotides to a growing strand of RNA

The figure shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

2

Rank the following mutations with respect to their likelihood of affecting the structure of the polypeptide (from most likely to affect structure to least likely). (1) insertion mutation in the middle of an intron (2) deletion of 3 bases crossing an intron-exon border (3) substitution mutation at the third position of a codon (4) substitution mutation at the second position of a codon

2,3,4,1

A sample of double-stranded DNA contains 28% thymine. Approximately what percent of the nucleotides in this sample will be guanine?

22%

A particular triplet of bases in the template strand of DNA is 5'-AAA-3'. The anticodon on the tRNA that binds the mRNA codon is __.

3'-AAA-5'

An mRNA molecule with the sequence 5'-CCG-ACG-3'is being read by a ribosome. During translation which of the following tRNA anticodons will be the first to productively bind with this mRNA?

3'-GGC-5'

Given a DNA molecule with the sequence of bases 5'-ATTGCA-3', what would be the sequence of the complementary strand? (It will be helpful to draw the DNA molecule when answering the question.)

3'-TAACGT-5'

A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. What would be the corresponding codon for the mRNA that is transcribed?

3'-UCA-5'

The sequence of nucleotides below is present at a DNA location where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence

5' A C G U U A G G 3'

A sample of double-stranded DNA contains 42% cytosine. Approximately what percent of the nucleotides in this sample will be thymine?

8%

DNA strands are antiparallel. Which of the following statements defines "antiparallel"?

A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true?

A gene from an organism can theoretically be expressed by any other organism

Which of the following statements best supports the one gene-one enzyme hypothesis?

A mutation in a single gene can result in a defective protein

Which of the following describes the most likely effect that a single base substitution in the middle of gene's sequence will have on the protein the gene encodes?

A single amino acid would change because pairing of mRNA and tRNA in the ribosome would change

During the elongation phase of translation, which site in the ribosome represents the first location where a codon pairs with an anticodon?

A site

Which of the following combinations of base pairs will be found in a molecule of DNA

A+C = G+T

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

A+G = C+T

Which of the following properties is associated with a protein that will be secreted from a eukaryotic cell?

Its signal sequence must target it to the ER

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

DNA ligase

What catalyzes the formation of phosphodiester bonds between a DNA strand and a new nucleotide being added during DNA replication?

DNA polymerase

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

DNA polymerase III

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel.

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that are joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

DNA polymerase synthesizes leading and lagging strands during replication only in one direction

Select the most accurate statement describing DNA replication complexes

DNA replication complexes are grouped into factories, which are anchored to the nuclear matrix

After DNA replication, the resulting daughter DNA double helix contains one strand of the original parental DNA and one new strand. What is the explanation for this phenomenon?

DNA replication is semiconservative

Meselson and Stahl cultured E. coli for several generations in a medium with a heavy isotope of nitrogen, 15N. They transferred the bacteria to a medium with a light isotope of nitrogen, 14 N. After two rounds of DNA replication, half the DNA molecules were light (both strands had 14N) and half were hybrids (15N-14N). What did the researchers conclude from these results?

DNA replication is semiconservative.

During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?

DNA synthesis can take place only in the 5' to 3' direction.

Which of the following shows the flow of genetic information?

DNA to RNA to protein

Which of the following is a reason that a new DNA strand elongates only in the 5' to 3' direction during DNA replication?

Dehydration reactions require a free -OH group

Which of the following mutations would likely be most dangerous to a cell?

Deletion of one nucleotide

DNA replication is said to be semiconservative. Which of the following statements correctly explains what this means?

Each new double helix consists of one old and one new strand

Which of the following investigators was (were) responsible for determining that DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine?

Erwin Chargaff

Which of the following statements describes the process of transformation in bacteria?

External DNA is taken into a cell, becoming part of the cell's genome

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?

Franklin

Which of the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur?

Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes

Which of the following statements correctly describes the structure of chromatin?

Heterochromatin is highly condensed, whereas euchromatin is less compact

Which of the following structural characteristics is most critical for the association between histones and DNA?

Histones are positively charged

Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?

Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction

Who performed classic experiments that supported the semiconservative model of DNA replication?

Meselson and Stahl

Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer that accomplishes this task in eukaryotes?

Messenger RNA is transcribed from a single gene and transfers information to the cytoplasm, where protein synthesis takes place

Which of the following best describes the redundancy in the genetic code

More than one codon can specify the addition of the same amino acid

The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact?

Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated

Which answer correctly compares prokaryotic and eukaryotic codons?

Organisms utilize codons that are nearly universal among all organisms

Which of the following statements is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress

What does a mutagen cause?

a change in the sequence of DNA

A single base substitution mutation is likely to have a less harmful effect when the base change results in which of the following?

a codon that specifies the same amino acid as the original codon

While characterizing an error-prone organism, researchers found that each of the following types of mutations occurred immediately downstream of the translation start site. Which type of mutation is likely to have the most serious effect on the function of the polypeptide product?

a deletion of two nucleotides

Which of these is currently considered the best definition of a gene?

a gene codes for either a polypeptide or an RNA molecule

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation?

a polypeptide missing an amino acid

A replication error results in a zygote that has inactive telomerase, which of the following characteristics would you expect to see in the organism that develops?

a reduction in chromosome length in gametes

Which of the following mutations would be most likely to have a harmful effect on an organism?

a single nucleotide insertion downstream of, and close to, the start of the coding sequence

Translation termination occurs when a ribosome interacts with which of the following structures?

a stop codon

Post-translational modifications of proteins may include which of the following processes?

addition of carbohydrates to form a glycoprotein

During mitosis, centromeres separate and chromatids become individual chromosomes during which phase?

anaphase

Accuracy in translation of mRNA into the primary structure of a polypeptide depends on specificity in the __.

attachment of amino acids to tRNAs

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase

A section of DNA has the base sequence shown in #1. A mutation in this DNA strand results in the base sequence shown in #2. What type of mutation does this change represent? #1 5' - AGCGTTACCGT-3' #2 5'-AGGCGTTACCGT-3'

frameshift mutation

The flow of information in a cell proceeds in what sequence?

from DNA to RNA to protein

In a nucleosome, the DNA is wrapped around

histones

Which of the following statements accurately describes differences between DNA replication in prokaryotes and DNA replication in eukaryotes?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many

If a bacteria contained a mutant aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA which of the following would occur?

Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU

Which of the following processes occurs as part of transcription?

RNA is synthesized

In eukaryotes, there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a protein?

RNA polymerase II

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript

Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis (select all that apply)

RNA polymerase, aminoacetyl-tRNA synthetase

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect?

Replication would not occur on either the leading or lagging strand

Which of the following statements about RNA processing is correct?

Ribozymes may function in RNA splicing

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. Which of the following best explains the effect of telomerase on cellular aging?

Telomerase can eliminate telomere shortening and slows aging

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

The leading strand is synthesized continuously in the 5'- 3' direction, while the lagging strand is synthesized discontinuously in the 5'- 3' direction

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication?

The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

Which of the following is most likely to occur if a researcher removes the 5' cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell?

The molecule will be degraded by enzymes

DNA is a self-replicating molecule. What accounts for this important property of DNA?

The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.

Which of the following statements correctly describes the difference between ATP used in metabolism and the nucleotides used as a building block during DNA synthesis?

The nucleotides have the sugar deoxyribose; ATP has the sugar ribose

Researchers found a strain of bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these results?

The proofreading mechanism of DNA polymerase was not working properly

Refer to the metabolic pathway illustrated. If I, II, III, and IV are all required for growth, a bacterial strain that does not make enzyme X would be able to grow on medium supplemented with which of the following nutrient(s)?

nutrients I and I only

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

one low-density and one intermediate-density band

Semiconservative replication involves a template. Which of the following best describes the template molecule?

one strand of the DNA molecule

Which of the following types of cells are affected most by telomere shortening?

only eukaryotic cells

Which component is directly involved in translation?

ribosome

Which of the following characteristics of DNA allows it to carry a vast amount of hereditary information?

sequence of bases

In eukaryotic cells, transcription cannot begin until

several transcription factors have bound to the promoter

Which of the following processes occurs in prokaryotes but not in eukaryotes?

simultaneous transcription and translation of the same mRNA

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?

single-strand DNA binding proteins

In his work with pneumonia-causing bacteria and mice, Griffith found that

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?

telomeres

In DNA polymerization, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?

the 3' OH

During _____of the cell cycle, the cell grows and replicates both its organelles and its chromosomes

interphase

After an RNA molecule is transcribed from a eukaryotic gene, what are removed, and what are spliced together, to produce an mRNA molecule with a continuous coding sequence?

introns, exons

As a result of its involvement in a chemical reaction, an enzyme

is unchanged by the reactants or products

Which of the following is true of DNA during interphase?

it exists as chromatin and is less condensed than mitotic chromosomes

Where does RNA polymerase begin transcribing a gene into mRNA

it starts after a certain nucleotide sequence called a promoter

What is the function of helicase in DNA replication?

it untwists the double helix and separates the two DNA strands

DNA is isolated from bacteria undergoing DNA replication. After heat treatment to disrupt H-bonds the DNA is centrifuged and it separates into two classes. One class of DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). Which types of DNA do the two classes most likely represent?

leading strands and Okazaki fragments

According to the central dogma, which of the following intermediate molecules correctly completes the flow chart describing the flow of information in a cell blank?DNA, __, Proteins

mRNA

Which of the following molecular structures contains codons?

mRNA

Which of the following molecules are produced by transcription? (select all that apply)

mRNA, ribozymes

Which of the following molecules directly participates in the process of translation?

mRNA, tRNA, and rRNA

In nucleotide excision repair, damaged DNA is excised by what enzyme(s)?

nuclease

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

nuclease, DNA polymerase, DNA ligase

Which list the provides the correct enzyme order required for nucleotide excision repair of a thymine dimer?

nuclease, DNA polymerase, DNA ligase

Which of the following lists represents the order of increasingly higher levels of organization of chromatin?

nucleosome, 30-nm chromatin fiber, looped domain

What process repairs damage to a preexisting double helix?

nucleotide excision repair

Refer to the metabolic pathway illustrated. If I, II, III and IV are all required for growth, a bacterial strain that does not make enzyme Y would be able to grow on medium supplemented with which of the following compounds?

nutrients A and C only

In eukaryotes which of the following is the first step in translation?

the small subunit of the ribosome recognizes and attaches near the 5' cap of mRNA

Which of the following characteristics is directly related to the coding of a single amino acid during the process of translation

the three-base sequence of mRNA

Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?

the transferred traits were heritable

In the structure of many eukaryotic genes, individual exons parallel which of the following?

the various domains of the protein product

A codon consists of ___ bases and specifies which __ will be inserted into the polypeptide chain

three, amino acid

In a DNA double helix an adenine of one strand always pairs with a(n) ___ of the complementary strand, and a guanine of one strand always pairs with a(n) ___ of the complementary strand

thymine...cytosine

In bacteria, what is the function of DNA polymerase III?

to add nucleotides to the 3' end of a growing DNA strand

Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?

transcription factors

Which of the following clues would tell you if a cell is prokaryotic or eukaryotic?

whether or not the cell is compartmentalized by internal membranes

How is translation initiated?

All of the listed answers are correct (the tRNA bearing methionine binds to the start codon ,the large ribosomal subunit binds to the small one, the start codon signals the start of translation, the small ribosomal subunit binds to the mRNA)

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in "heavy" (radioactive) nitrogen (15N) for several generations and then transfer them to 14N medium. Which pattern in the figure would you expect if the DNA was replicated in a conservative manner?

B

Which of the following is most likely to result from reduced or very little active telomerase activity?

Cells age and begin to lose function

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (15N) and then transferred them to a medium containing 14N (non-radioactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

D

Hershey and Chase set out to determine which type of molecule is used for genetic inheritance. They completed a series of experiments where E. coli was infected by a T2 virus. Which molecular component of the T2 virus ended up inside the cell?

DNA

What are chromosomes made of?

DNA and proteins

Which of the following characteristics allowed Hershey and Chase to determine whether the genetic material was made of DNA or protein?

DNA contains phosphorus, whereas protein does not

Radioactive thymine is added to media containing one actively dividing E. coli bacterium. Which of the following outcomes would be seen after a single cell division?

DNA in both daughter cells would be radioactive

Within a double-stranded DNA molecule, if adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine what consequence in the structure of the DNA?

It permits complementary base pairing

What is the function of the release factor during translation in eukaryotes?

It binds to the stop codon in the A site in place of a tRNA

Which of the following processes correctly describes alternative RNA splicing?

It can allow the production of proteins of different sizes and functions from a single mRNA

Which of the following is true of a codon?

It can be either in DNA or in RNA

Which of the following statements best describes the significance of the TATA box in the promoters of eukaryotes

It is the recognition site for the binding of a specific transcription factor

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together

In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

No replication fork will be formed.

Which one of the following statements is true of tRNAs?

None of the listed answers are correct (There are four types of tRNA, Each tRNA binds a particular codon, tRNAs are double-stranded, tRNAs carry special sequences known as codons)

Which of the following is true of RNA processing

Nucleotides are added at both ends of the RNA

Your body contains tens of thousands of different proteins, each with a specific structure and function. The unique three-dimensional shape of each of these diverse proteins is based on several superimposed levels of structure. Which of the following is an accurate statement about proteins?

The primary structure of a protein is the order of amino acids in a polypeptide, as coded for by the DNA of a g

Two students decided to repeat the Hershey and Chase experiment, with modifications. Like Hershey and Chase they used radioactive sulfur but they substituted radioactive nitrogen for radioactive phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Which of the following is the biggest shortcoming in their experimental design?

The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen

Which of the following best explains the observation that in bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs?

The rules for base pairing between the third base of a codon and tRNA are flexible

Which of the following statements is the most current description of a gene?

a DNA sequence that is expressed to form a functional RNA or polypeptide product

Which of the following changes in an exon is most likely to result in a nonfunctional protein product?

a base-pair deletion

What is a ribozyme?

a biological catalyst made of RNA

In the Hershey and Chase experiment that helped confirm DNA, not protein, was the hereditary material, what was the key finding?

radioactively-labeled phosphorus was present inside the infected bacteria

What is the function of the enzyme topoisomerase in DNA replication?

relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. Which of the following is most likely to result if the rate of repair lags behind the rate of mutation?

the cell can be transformed into a cancerous cell

Which of the following is most likely to result if a cell is unable to produce histone proteins?

the cell's DNA could not be packed into its nucleus

What are telomeres?

the ends of linear chromosomes

Which answer correctly compares the primary transcript in the nucleus of a eukaryotic cell with the functional mRNA?

the primary transcript is larger than the mRNA

Which answer correctly compares the primary transcript in a prokaryotic cell with the functional mRNA?

the primary transcript is the same size as the mRNA