DNA Structure and Function Quiz

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Questions and Answers

Pair up the nucleotide bases with their complementary partners.

A = Thymine T = Adenine C = Guanine G = Cytosine

Write the complementary sequence for the following DNA sequence, in order from 3' to 5': 5′−CGATATTGAGCTAAGCTT−3′

3′− GCTATAACTCGATTCGAA −5′

Rank the following base pairs according to their stability. Rank from most to least stable

Pairing usually is ranked as: GC > AT

If you measure the amounts of the bases in any sample of DNA, you'll find that the amount of A + the amount of G equals the amount of T + the amount of C.

True Signup and view all the answers

Which statement expresses a real difference between DNA and RNA?

DNA is much longer than RNA. Signup and view all the answers

What holds the strands of the DNA double helix together?

Hydrogen bonds between purines and pyrimidines. Signup and view all the answers

If you were to analyze a DNA sample from a eukaryotic cell, you would find that:

The number of purines equals the number of pyrimidines; the number of guanines equals the number of cytosines. Signup and view all the answers

The building blocks or monomers of nucleic acid molecules are called

Nucleotides. Signup and view all the answers

The flow of genetic information in a cell goes from

DNA to RNA to protein. Signup and view all the answers

When nucleotides polymerize to form a nucleic acid

A covalent bond forms between the sugar of one nucleotide and the phosphate of a second. Signup and view all the answers

In the accompanying image, a nucleotide is indicated by the letter

B. Signup and view all the answers

Which of these is a difference between a DNA and an RNA molecule?

True Signup and view all the answers

This is an image of a(n)

Nucleotide. Signup and view all the answers

The letter A indicates a

Phosphate group. Signup and view all the answers

A nitrogenous base is indicated by the letter

C. Signup and view all the answers

You can tell that this is an image of a DNA nucleotide and not an RNA nucleotide because you see a

Sugar with two, and not three, oxygen atoms. Signup and view all the answers

Which of these nitrogenous bases is found in DNA but not in RNA?

Thymine. Signup and view all the answers

Which of these is(are) pyrimidines?

C, D, and E. Signup and view all the answers

In a nucleotide, the nitrogenous base is attached to the sugar's _ carbon and the phosphate group is attached to the sugar's _ carbon.

1'... 5'. Signup and view all the answers

Nucleic acids are assembled in the _____ direction.

5' to 3'. Signup and view all the answers

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. Signup and view all the answers

This is an image of a

Phage. Signup and view all the answers

Who demonstrated that DNA is the genetic material of the T2 phage?

Hershey and Chase. Signup and view all the answers

The radioactive isotope 32P labels the T2 phage's

DNA. Signup and view all the answers

Hershey and Chase used _____ to radioactively label the T2 phage's proteins.

35S. Signup and view all the answers

After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _, which demonstrated that _ is the phage's genetic material.

Labeled DNA...DNA. Signup and view all the answers

In his transformation experiments, what did Griffith observe?

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. Signup and view all the answers

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%. Signup and view all the answers

Drag the labels to their appropriate locations on the diagram below.

Refer to the indicated diagram. Signup and view all the answers

Each of the four images below shows a strand of template DNA (dark blue) with an RNA primer (red) to which DNA pol III will add nucleotides. In which image will adenine (A) be the next nucleotide to be added to the primer?

Refer to the indicated images. Signup and view all the answers

Drag the arrows onto the diagram below to indicate the direction that DNA polymerase III moves along the parental (template) DNA strands at each of the two replication forks.

Refer to the indicated diagram. Signup and view all the answers

Sort the phrases into the appropriate bins depending on which protein they describe.

Refer to the indicated phrases. Signup and view all the answers

Drag each phrase to the appropriate bin depending on whether it describes the synthesis of the leading strand, the synthesis of the lagging strand, or the synthesis of both strands.

Refer to the indicated phrases. Signup and view all the answers

Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.

Refer to the indicated primers. Signup and view all the answers

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many. Signup and view all the answers

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

No replication fork will be formed. Signup and view all the answers

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. Signup and view all the answers

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

It joins Okazaki fragments together. Signup and view all the answers

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

Single-strand DNA binding proteins. Signup and view all the answers

Which of the following would you expect of a eukaryote lacking telomerase?

A reduction in chromosome length in gametes. Signup and view all the answers

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

D. Signup and view all the answers

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

The cell's DNA couldn't be packed into its nucleus. Signup and view all the answers

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged. Signup and view all the answers

Which of the following statements describes chromatin?

Heterochromatin is highly condensed, whereas euchromatin is less compact. Signup and view all the answers

Drag each item to the appropriate bin.

Refer to the indicated items. Signup and view all the answers

What amino acid sequence does the following mRNA nucleotide sequence specify? 5′−AUGGCAAGAAAA−3′

Met-Ala-Arg-Lys. Signup and view all the answers

What amino acid sequence does the following DNA nucleotide sequence specify? 3′−TACAGAACGGTA−5′

Met-Ser-Cys-His. Signup and view all the answers

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

From DNA to RNA to protein. Signup and view all the answers

A codon consists of _ bases and specifies which _ will be inserted into the polypeptide chain.

Three...amino acid. Signup and view all the answers

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'. Signup and view all the answers

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

<ol start="2"> <li></li> </ol> Signup and view all the answers

In the process of transcription,

RNA is synthesized. Signup and view all the answers

Which of the following specifies a single amino acid in a polypeptide chain?

The three-base sequence of mRNA. Signup and view all the answers

In the diagram below, the gray unit represents

RNA polymerase. Signup and view all the answers

In the diagram below, the green unit represents

The promoter. Signup and view all the answers

In the diagram below, the two blue strands represent

DNA. Signup and view all the answers

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

GTTACG = CAAUGC Signup and view all the answers

The direction of synthesis of an RNA transcript is

5' —> 3'. Signup and view all the answers

Where does RNA polymerase begin transcribing a gene into mRNA?

It starts after a certain nucleotide sequence called a promoter. Signup and view all the answers

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

Several transcription factors. Signup and view all the answers

During RNA processing a(n) _____ is added to the 5' end of the RNA.

Modified guanine nucleotide. Signup and view all the answers

During RNA processing a(n) _____ is added to the 3' end of the RNA.

A long string of adenine nucleotides. Signup and view all the answers

Spliceosomes are composed of

snRNPs and other proteins. Signup and view all the answers

The RNA segments joined to one another by spliceosomes are

Exons. Signup and view all the answers

Translation occurs in the

Cytoplasm. Signup and view all the answers

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. Signup and view all the answers

Alternative RNA splicing

Can allow the production of proteins of different sizes and functions from a single gene. Signup and view all the answers

E = exon and I = intron. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'. Which components of the previous molecule will also be found in mRNA in the cytosol?

5' UTR E1 E2 E3 E4 UTR 3'. Signup and view all the answers

Drag the labels to the appropriate targets to identify where in the cell each process associated with protein synthesis takes place.

Refer to the indicated labels. Signup and view all the answers

Drag the labels to the appropriate bins to identify the step in protein synthesis where each type of RNA first plays a role. If an RNA does not play a role in protein synthesis, drag it to the 'not used in protein synthesis' bin.

Refer to the indicated labels. Signup and view all the answers

Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that there are only 2 bases (A and T) in the Martian DNA, and there are only 17 amino acids found in Martian proteins. Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms?

5 bases. Signup and view all the answers

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.

Refer to the indicated words. Signup and view all the answers

A particular triplet of bases in the coding strand of DNA is AAA. The anticodon on the tRNA that binds this mRNA codon is

UUU. Signup and view all the answers

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

Binding of the anticodon to the codon and the attachment of amino acids to tRNAs. Signup and view all the answers

The release factor (RF)

Binds to the stop codon in the A site in place of a tRNA. Signup and view all the answers

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

Hydrogen bonding between base pairs. Signup and view all the answers

The tRNA shown in the figure above has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

The amino acid binds covalently. Signup and view all the answers

During elongation, which site in the ribosome represents the location where a codon is being read?

A site. Signup and view all the answers

How does termination of translation take place?

A stop codon is reached. Signup and view all the answers

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

A deletion of two nucleotides. Signup and view all the answers

What does a mutagen cause?

A change in the sequence of DNA. Signup and view all the answers

A nonsense mutation in a gene

Introduces a premature stop codon into the mRNA. Signup and view all the answers

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in

A polypeptide missing an amino acid. Signup and view all the answers

How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?

Only a single amino acid could change, because the reading frame is unaffected. Signup and view all the answers

_____ bind(s) to DNA enhancer regions.

Activators. Signup and view all the answers

Which of these indicates an enhancer region?

A. Signup and view all the answers

Which of these directly bind(s) to the promoter?

C and D. Signup and view all the answers

DNA methylation is a mechanism used by eukaryotes to do what?

Inactivate genes. Signup and view all the answers

Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?

The mutant will show low levels of gene expression. Signup and view all the answers

Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread

Alternative splicing. Signup and view all the answers

Which of the following would be most likely to lead to cancer?

Amplification of a proto-oncogene and inactivation of a tumor-suppressor gene. Signup and view all the answers

The product of the p53 gene

Inhibits the cell cycle. Signup and view all the answers

Forms of the Ras protein found in tumors usually cause which of the following?

Excessive cell division. Signup and view all the answers

How are genes coordinately controlled in eukaryotic cells? Select all that apply.

Coordinately controlled genes in eukaryotic cells are activated by the same chemical signals; Coordinately controlled genes in eukaryotic cells share a set of control elements. Signup and view all the answers

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?

Short-lived proteins enable the cells to control their activities precisely and efficiently. Signup and view all the answers

Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?

The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time. Signup and view all the answers

We describe DNA as the hereditary material of an organism. What does it mean for something to be hereditary?

It must be passed from one generation to the next. Signup and view all the answers

If I wanted to radioactively label proteins (but not DNA, RNA, sugars, or lipids) which of the following radioactive isotopes would I use?

Sulfur 35 (S35). Signup and view all the answers

This is some of the original data that Chargraff collected in 1950. What do you notice about the relative percentages of each of these nucleotides?

A and T are always found at similar rates and C and G are always found at similar rates. Signup and view all the answers

This is some of the original data that Chargraff collected in 1950. Why do you think that the percentages for A and T are similar but not exact?

The actual percentages are exact, but the data are not perfect. Signup and view all the answers

Study Notes

Nucleotide Pairing and DNA Structure

Adenine pairs with Thymine, and Guanine pairs with Cytosine, forming stable hydrogen bonds in DNA.
The complementary DNA sequence for 5′−CGATATTGAGCTAAGCTT−3′ is 3′−GCTATAACTCGATTCGAA−5′.
Base pair stability rankings typically place G-C pairs above A-T pairs due to their triple hydrogen bonds compared to double bonds.

DNA Composition and Function

Chargaff's rules: A + G = T + C. The ratios of nucleotide bases in DNA are consistent across samples.
DNA molecules are longer than RNA molecules, contributing to their differing functions in storage versus use of genetic information.
Nucleotides serve as the basic building blocks of nucleic acids, linked by covalent bonds between their sugar and phosphate groups.

Genetic Information Flow

The central dogma of molecular biology: DNA → RNA → Protein. This flow governs gene expression.
Genes are transcribed into mRNA, then translated into proteins, with each amino acid coded for by a three-base codon in mRNA.

Transcription and RNA Processing

RNA polymerase initiates transcription at a promoter region and synthesizes RNA in a 5' to 3' direction.
Eukaryotic RNA undergoes processing: the addition of a 5' cap (modified guanine) and a poly-A tail, while introns are removed and exons are spliced together.

Translation Mechanism

Translation occurs in the cytoplasm, with tRNA molecules bringing amino acids to the growing polypeptide chain.
The ribosome consists of P (peptidyl) and A (aminoacyl) sites where tRNA binds codons on the mRNA.
Release factors bind to stop codons, terminating the translation process.

Mutations and Their Effects

Mutations can arise from various factors, including deletions and substitutions; some can introduce premature stop codons.
The most common mutation in cystic fibrosis involves a deletion causing a missing amino acid in a polypeptide.

Gene Regulation

Gene expression is controlled through mechanisms like DNA methylation and histone modification.
Activators bind to enhancer regions, influencing the transcription of coordinate genes through shared control elements.

Cancer Biology

Mutations in proto-oncogenes and tumor-suppressor genes can lead to uncontrolled cell division, facilitating cancer.
The product of the p53 gene plays a critical role in inhibiting the cell cycle, maintaining genomic stability.

Key Concepts

Histones help package DNA into nucleosomes, and their acetylation status influences gene expression levels.
Alternative RNA splicing allows for the production of different proteins from a single gene, expanding functional diversity.
Hereditary attributes are passed down through generations due to the stability and replication fidelity of DNA.

Experimental Techniques

The Hershey and Chase experiment utilized radioactive isotopes to demonstrate that DNA, not protein, is the genetic material.
Meselson and Stahl's experiments provided evidence for semiconservative DNA replication, identifying the roles of different nitrogen isotopes.

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Description

Test your knowledge on nucleotide pairing, DNA structure, and the flow of genetic information. This quiz covers key concepts including Chargaff's rules, the central dogma of molecular biology, and the stability of DNA base pairs. Perfect for students studying molecular biology or genetics.