BIO 102 Exam 2

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

2

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

22%

The anticodon of a particular tRNA molecule is ________.

complementary to the corresponding mRNA codon

Jennifer Doudna discovered CRISPR-Cas9 due to its role in which of the following?

defending bacteria against bacteriophage infection

The elongation of the leading strand during DNA synthesis ________.

depends on the action of DNA polymerase

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

simultaneous transcription and translation of the same mRNA

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'

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'

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 is most likely to result from reduced or very little active telomerase activity?

Cells age and begin to lose function.

Exposure to the UV radiation in sunlight causes DNA changes in skin cells. Why are these changes more harmful when they occur in an individual with xeroderma pigmentosum (XP) than in an individual who does not have this disorder?

Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes.

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

DNA polymerase

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.

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 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

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

It joins Okazaki fragments together.

What amino acid sequence will be generated based on the following mRNA codon sequence?5′-AUG-UCU-UCG-UUA-UCC-UUG-3′

Met-Ser-Ser-Leu-Ser-Leu

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 is a reason that the low error rate of DNA replication is important to evolution?

Rare errors are the source of variation

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

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.

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.

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.

A particular triplet of bases in the coding sequence of DNA is 5'-AAA-3'. The anticodon on the tRNA that binds the mRNA codon is ________.

UUU

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

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

Which component is directly involved in translation?

a ribosome

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

a site

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

a stop codon

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. These results best support which of the following conclusions.

a substance had been transferred from pathogenic to nonpathogenic bacteria

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

addition of carbohydrates to form a glycoprotein

Using the CRISPR-Cas9 system to correct a genetic defect in a mouse brings with it which of the following risks?

altering non-target mouse genes needed for cell function

Rosalind Franklin's X-ray crystallography data suggested DNA is double stranded and has a uniform diameter. These observations can be used to rule out base pairing between two of the same nucleotide because ________.

an A-A pair is wider than a C-C pair

Which of the following processes will occur at the exposed 3′ end of a tRNA molecule?

an amino acid will bind covalently

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

base-pair deletion

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

In a nucleosome, the DNA is wrapped around ________.

histones

What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?

hydrogen bonding between base pairs

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 properties is associated with a protein that will be secreted from a eukaryotic cell?

its signal sequence must target it to the ER

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 carries information from DNA and directs incorporation of amino acids at the ribosome?

mRNA

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

mRNA, tRNA, and rRNA

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

nucleosome, 30-nm chromatin fiber, looped domain

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

one strand of the DNA molecule

Which answer correctly compares prokaryotic and eukaryotic codons?

organisms utilize codons that are nearly universal among all organisms

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

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

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

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

Histone proteins contain internal cores that are hydrophobic and surface amino acids that are positively charged. Which of the following characteristics of DNA would best support tight binding between DNA and histones?

the ring structures in DNA bases that disperse charge promote hydrophobic interactions with histone cores

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

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

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

the various domains of the polypeptide products

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

transcription factors