Molecular Genetics Module 2 Quiz

Questions and Answers

Which cluster of RNA molecules is not correctly listed?

16S rRNA, 5S rRNA, 23S rRNA

16S rRNA, 5S rRNA, and 23S rRNA

18S rRNA, 5.8S rRNA, and proteins (correct)

12S rRNA, 5.8S rRNA, and proteins (correct)

What does the anticodon on the tRNA molecule do?

Binds to the mRNA in a complementary fashion

What is the result of transcribing the sequence AATGCGGTC?

UUACGCCAG

What hypothesis was supported by the observation made by Crick and co-workers regarding base additions or deletions?

The code is a triplet Signup and view all the answers

If the following DNA strand was used as a template, what would be the sequence of the RNA? 5' GTACCGTC 3'

5' GACGGUAC 3' Signup and view all the answers

What is the initiator triplet in both prokaryotes and eukaryotes, and what amino acid is recruited by this triplet?

AUG, methionine Signup and view all the answers

In prokaryotes, translation of an mRNA is coupled to what process?

Transcription Signup and view all the answers

Which terms accurately reflect the nature of DNA replication in prokaryotes?

Bidirectional Signup and view all the answers

What is unusual about the amino acid composition of histones?

Histones contain large amounts of positively charged amino acids such as lysine and arginine Signup and view all the answers

If a DNA molecule of 50 base pairs contains 15 cytosine bases (C), how many thymine bases will it have?

35 Signup and view all the answers

If a DNA molecule is 30% cytosine (C), what is the percentage of guanine (G)?

30% Signup and view all the answers

How can replication of DNA in vivo be accurately described?

Semiconservative Signup and view all the answers

What does enhanced post-translational modification of a protein include?

Removal or modification of terminal amino acids Signup and view all the answers

What would Hershey and Chase have concluded if phage ghosts contained 32P label but were absent from infected E. coli?

That protein was the genetic material in phage Signup and view all the answers

What chemical group is found at the 5' end of a DNA molecule?

Phosphate group Signup and view all the answers

What three possible models were suggested to describe the nature of DNA replication?

Semiconservative, dispersive, and conservative replication Signup and view all the answers

Which of the following statements are true about enhancers?

Enhancers represent control elements located far from the promoter Signup and view all the answers

True or False: Enhancers are recognized by and bind directly to RNA polymerase.

False Signup and view all the answers

When examining the genetic code, it is apparent that...

There can be more than one codon for a particular amino acid Signup and view all the answers

True or False: The genetic code is ambiguous in that the same codon can code for two or more amino acids.

False Signup and view all the answers

What is the role of tRNA?

To act as transporters bringing amino acids to the site of protein synthesis Signup and view all the answers

The one-gene, one-enzyme hypothesis emerged from work on which two organisms?

Neurospora and Drosophila Signup and view all the answers

Hairpins are formed in DNA as a result of what?

Sequences on the same strand that are inverted and complementary Signup and view all the answers

If one compares the base sequences of related genes from different species, what is usually conserved?

Corresponding exons are usually conserved, but the sequences of introns are much less well conserved Signup and view all the answers

What are amino acids?

They are the building blocks of proteins; tRNA brings them to the ribosome for protein synthesis; there are more than 20 of them required in the body. Signup and view all the answers

What secondary structures are formed when single-stranded DNA or RNA is inverted and complementary?

Hairpin Signup and view all the answers

Which of the following are among the major components of prokaryotic ribosomes?

16S rRNA Signup and view all the answers

Match the term with the best letter choice: DNA primase

DNA primase = b. RNA primer synthesis Signup and view all the answers

Where are amino acids with hydrophobic side chains most likely to be located within a protein?

Away from the surface of the protein, inside the hydrophobic core of the protein (folded inside) Signup and view all the answers

List 3 requirements of any substance that is considered genetic material.

<ol> <li>The storage of information to control the growth and metabolism of the cell; 2. Have sufficient stability to be faithfully copied from generation of cells to the next; 3. Possess a great degree of mutability.</li> </ol> Signup and view all the answers

Of the following three types of nucleic acids—DNA, mRNA, tRNA— which is most likely to contain modified bases?

tRNA Signup and view all the answers

What form of DNA replication was eliminated during the Meselson-Stahl experiment?

Conservative replication Signup and view all the answers

A procedure that is often used to separate molecules by using their molecular charges is called ________

Electrophoresis (Gel electrophoresis) Signup and view all the answers

What are the three classes of 'functional' RNAs (not including mRNA)?

<ol> <li>tRNA - brings correct amino acid to the mRNA during translation; 2. rRNA - major component of ribosomes; 3. snRNA - helps process RNA transcripts, especially by removing introns.</li> </ol> Signup and view all the answers

Briefly define transformation.

Transformation is the process whereby one organism is genetically altered by exposure to DNA from another organism. Signup and view all the answers

What are the four nucleotides that make up RNA? Give full names, not abbreviations.

Adenine, Guanine, Cytosine, Uracil Signup and view all the answers

Name an observation that supports the view that the genetic code may be ordered.

Amino acids that are chemically similar share the middle base of their respective codons. Signup and view all the answers

What are the two major types of 'upstream' signals involved in the initiation of transcription by RNA polymerase II?

Regulatory sequences and transcription factors. Signup and view all the answers

What is meant by the term antiparallel?

5' to 3' directionality of two strands running in opposite directions Signup and view all the answers

What is the enzyme that lays down the initial nucleotides to set up a condition for replication?

Primase Signup and view all the answers

Which of the following relations will be found in the percentages of bases of a double-stranded DNA molecule? A + G = T + C

True Signup and view all the answers

Which of the following relations will be found in the percentages of bases of a double-stranded DNA molecule? A + C = G + T

True Signup and view all the answers

Which of the following relations will be found in the percentages of bases of a double-stranded DNA molecule? A + T / A + G = 1.

False Signup and view all the answers

What is exon shuffling?

Functional regions of genes in eukaryotes consist of collections of exons originally present in ancestral generations that are brought together through various recombination events over time. Signup and view all the answers

Briefly define the term 'autoradiography'. Identify a classic experiment that used autoradiography to determine the replicative nature of DNA in eukaryotes.

Autoradiography is a technique that allows an isotope to be detected within a cell. Taylor, Woods, and Hughes experiment utilizing 3-H Thymidine. Signup and view all the answers

What are the 3 nucleotides that make up RNA?

Adenine, Guanine, Cytosine, Uracil. Signup and view all the answers

Describe hydrophobic interactions, hydrogen bonds, and disulfide bridges as they relate to protein structure.

Hydrophobic interactions: Nonpolar side chains of amino acids tend to associate to form hydrophobic clusters usually away from the protein surface. Hydrogen bonds: Such bonds may occur between components of the peptide bond, the side chains, or a combination of the two. They are responsible for helical and pleated sheet structures of proteins. Disulfide bridges: Such bonds are formed between two cysteine side chains and represent relatively strong attractive forces between different regions of proteins. Signup and view all the answers

Describe the role of the various types of nucleic acids in the storage and expression of information in living organisms.

Information contained in the base sequences of DNA is transcribed into a variety of RNAs. Certain RNAs (tRNA) carry amino acids to the site of translation where proteins are assembled. Other RNAs (mRNA and rRNA) provide a mechanism for ordering the sequence of amino acids in proteins. Signup and view all the answers

Uridine contains ______ as sugar.

ribose Signup and view all the answers

Describe the function of N-formylmethionine in prokaryotes.

N-formylmethionine serves as the initiator in prokaryotic translation. Signup and view all the answers

Which of the following DNA double helices would be more difficult to separate into single-stranded molecules by treatment with heat?

CGTAATCCCGTAGGG Signup and view all the answers

When this molecule is synthesized, what templates are used?

DNA only Signup and view all the answers

What form of DNA replication was eliminated during the Meselson-Stahl experiment?

Conservative Replication Signup and view all the answers

List two types of small RNA molecules involved in gene regulation.

siRNA, miRNA Signup and view all the answers

This method of replication preserves the covalent links on one strand of DNA but allows permanent separation of the 'parental' double helix to form two templates.

Semiconservative replication Signup and view all the answers

Suppose that in the use of polynucleotide phosphorylase A and C are present in a ratio of 1A:5C. What is the probability that an AAA sequence will occur?

(1/6) x (1/6) x (1/6) Signup and view all the answers

The code is nonoverlapping, meaning that, assuming 'standard translation' a given base participates in the specification of _________ amino acid(s).

one and only one Signup and view all the answers

This new strand of DNA has its 3' end oriented in the same direction as the replication fork travels.

Leading strand Signup and view all the answers

What enzyme is exploited to produce synthetic mRNAs?

Polynucleotide phosphorylase Signup and view all the answers

Which of the following enzymes are known to be involved in the replication of DNA in bacteria?

DNA Polymerase I Signup and view all the answers

The β chain of adult hemoglobin is composed of 146 amino acids of a known sequence. In comparing the normal β chain with the β chain in sickle cell hemoglobin, what alteration is one likely to find?

Valine instead of glutamic acid in the 6th position Signup and view all the answers

Significant in deciphering the genetic code was the discovery of the enzyme polynucleotide phosphorylase. What was this enzyme used for?

The manufacture of synthetic RNA for cell-free systems Signup and view all the answers

The basic structure of a nucleotide includes the following components:

Base, sugar, and phosphate Signup and view all the answers

Which of the following two terms relates most closely to split genes?

Introns, exons Signup and view all the answers

In eukaryotes, tRNAs are

Transcribed in the nucleus, but function in the cytoplasm Signup and view all the answers

A short segment of an mRNA molecule is shown: 5'-AUGGUGCUGAAG. Assume that a mutation in the DNA occurs so that the fourth base of the messenger RNA now reads A rather than G. What sequence of amino acids will the mRNA now code for?

Methionine-methionine-leucine-lysine Signup and view all the answers

Which is not true of amino acids?

All of the above are true Signup and view all the answers

The long-term storage of genetic information in a cell occurs in the:

DNA Signup and view all the answers

What additive did Meselson and Stahl initially supply to the medium to distinguish 'new' from 'old' DNA?

15-N Signup and view all the answers

In the classic experiment conducted by Hershey and Chase, why was the pellet radioactive in the centrifuge tube that contained bacteria with viruses?

The bacteria were in the pellet, and many contained the radioactive viral DNA. Signup and view all the answers

The primary structure of a protein is determined by:

The sequence of amino acids. Signup and view all the answers

Select three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes.

5'-capping, 3'-poly(A) tail addition, splicing Signup and view all the answers

Translation is directly dependent on all of the following associations except _______.

Complementary base pairing between mRNA and DNA Signup and view all the answers

If a DNA molecule is 30% cytosine (C), what is the percentage of guanine (G)?

30% Signup and view all the answers

What is the chromosomal configuration of phiX174 virus?

Single stranded DNA circular Signup and view all the answers

Why do introns not interrupt the coding of a particular protein?

Introns are removed from mRNA before translation. Signup and view all the answers

In the analysis of the nucleotide composition of double-stranded DNA, which of the following would be true?

A + C = G + T Signup and view all the answers

The 'RNA World' theory suggests that:

RNA was the genetic material in the first living cells. Signup and view all the answers

Match the following events in the pre-RNA processing of a one intron-two exon gene in correct sequence order:

Transcription of the DNA template into the pre-mRNA molecule = 1 Addition of the 5' Cap = 2 Recognition and binding the 3' AAUAAA sequence by specific protein factors = 3 Attachment of snRNP U1 to the 5' splice site = 4 Transesterification reaction at the branch point adenine = 5 Cleavage at the poly(A) site = 6 Release of lariat structure = 7 Splicing together of exons = 8 Addition of poly(A) tail = 9 Export to the cytoplasm = 10 Signup and view all the answers

Why did fragment B remain double-stranded at 89°C compared to fragment A?

Fragment B likely has a greater G-C content compared to Fragment A. Signup and view all the answers

Match eukaryotic RNA polymerases with what they transcribe:

RNA Pol I = rRNA RNA Pol II = mRNA and snRNA RNA Pol III = tRNA, rRNA, and snRNA Signup and view all the answers

Which of the following are roles of the 5' cap? Select all that are true.

The cap protects the RNA from degradation. Signup and view all the answers

Electrophoretic separation of HbA from HbS is based on a difference in their:

Charges Signup and view all the answers

_____________ is seen primarily among prokaryotes where one mRNA carries coding information for more than one protein.

Polycistronic mRNA Signup and view all the answers

During the polymerization of nucleic acids, covalent bonds are formed between neighboring nucleotides. Which carbons are involved in such bonds?

3' and 5' Carbons Signup and view all the answers

In transcription, nucleotides are always added to the _____ end of the elongating strand.

3' end because transcription runs 5' to 3'. Signup and view all the answers

Of what importance might antisense oligonucleotides have in human health?

Antisense oligonucleotides can be used in gene therapy to shut off malfunctioning genes. Signup and view all the answers

RNA differs from DNA in that it:

Has uracil rather than thymine Signup and view all the answers

List the components of a nucleosome.

A nucleosome is composed of 2 turns of DNA wrapped around a set of 8 proteins called histones. Signup and view all the answers

RNA polymerase must bind to a region of DNA called a(n)_______ in order to begin transcription.

Promoter Signup and view all the answers

The spliceosome is a large enzyme that catalyzes the removal of:

Introns in pre mRNAs Signup and view all the answers

In eukaryotes, tRNAs are:

Transcribed in the nucleus, but function in the cytoplasm. Signup and view all the answers

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which fact?

DNA contains phosphorus, but protein does not. Signup and view all the answers

Which of these sequences, if paired with its complementary strand, would be a palindrome?

5' CCCGGG 3' Signup and view all the answers

Which of the following clusters of terms accurately describes DNA as it is generally viewed in prokaryotes and eukaryotes?

Double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C + T) = 1.0 Signup and view all the answers

What chemical group is found at the 3' end of a DNA molecule?

Hydroxyl group Signup and view all the answers

Select three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes.

5'-capping, 3'-poly(A) tail addition, splicing Signup and view all the answers

In each round of the elongation cycle of protein synthesis, a new _ binds to the codon in the _ site.

aminoacyl-tRNA, A Signup and view all the answers

In each round of the elongation cycle of protein synthesis, the peptide is transferred from the tRNA in the _______ site to the new aminoacyl-tRNA.

P Signup and view all the answers

Finally, the entire _______ moves along the mRNA in a 5' to 3' direction.

ribosome Signup and view all the answers

In one strand of DNA, the nucleotide sequence is 5'-ATGC-3'. The complementary sequence in the other strand must be:

3'-TACG-5' Signup and view all the answers

Which of the following are among the major components of prokaryotic ribosomes?

70S ribosomal RNA Signup and view all the answers

Study Notes

Exon Shuffling

Exon shuffling refers to the recombination of exons from ancestral genes, leading to functional gene diversity in eukaryotes.
This process is enhanced by the presence of introns during genetic crossing over.

Autoradiography

Autoradiography is a technique for detecting isotopes within cells.
Key experiment by Taylor, Woods, and Hughes used 3-H Thymidine to confirm DNA's replicative nature.

RNA Nucleotides

RNA consists of four nucleotides: Adenine, Guanine, Cytosine, and Uracil.

Protein Structure Phenomena

Hydrophobic interactions: Nonpolar amino acids cluster away from water, influencing protein shape.
Hydrogen bonds: Form between side chains or peptide bonds, stabilizing helical and pleated structures.
Disulfide bridges: Formed between cysteine residues, providing strong links across protein regions.

Nucleic Acids and Information Storage

DNA's base sequences are transcribed into RNAs, which play roles in protein synthesis.
tRNA carries amino acids, while mRNA and rRNA help sequence amino acids into proteins.

Uridine Sugar Component

Uridine contains ribose as its sugar component.

Prokaryotic Translation Initiator

N-formylmethionine is the initiating amino acid in prokaryotic translation.

DNA Helix Stability

DNA molecule B is more stable due to higher G-C content compared to A, making it harder to separate under heat.

RNA Synthesis Template

Only DNA acts as a template for RNA synthesis, not the reverse.

Meselson-Stahl Experiment

Conservative replication was disproved as the original double-helix was not preserved during division.

Small RNA in Gene Regulation

siRNA and mRNA are involved in regulating gene expression.

DNA Replication Method

Semiconservative replication allows one strand to preserve its covalent links while forming two templates.

Polynucleotide Phosphorylase

This enzyme synthesizes synthetic RNA molecules.

Bacterial DNA Replication Enzymes

Key enzymes in bacterial DNA replication include Ligase, RNA primase, and DNA Polymerase I.

Sickle Cell Hemoglobin Mutation

Alteration of the β chain results in valine replacing glutamic acid at the 6th position.

Polynucleotide Phosphorylase in RNA Synthesis

Used for creating synthetic RNA in lab environments.

Nucleotide Structure

A nucleotide consists of a base, sugar, and phosphate group.

Split Genes

Introns and exons are terms closely related to split genes in genetic encoding.

tRNA Function

In eukaryotes, tRNAs are transcribed in the nucleus before functioning in the cytoplasm.

mRNA Mutation Effects

A mutation in mRNA could lead to changes in amino acid coding, e.g., a single base change affects protein sequence.

Amino Acid Truths

The statement "all amino acids are building blocks of proteins" is true; there are 20 essential amino acids for the body.

Long-term Genetic Storage

Genetic information is stably stored in DNA within cells.

Distinguishing DNA in E. Coli

In the Meselson-Stahl experiment, 15-N was utilized to differentiate old from new DNA strands.

Hershey-Chase Experiment Outcomes

The pellet in the centrifuge contained bacteria, which incorporated radioactive viral DNA proving DNA as the genetic material.

Primary Protein Structure

The sequence of amino acids determines a protein's primary structure.

mRNA Maturation Process

Maturation of mRNA includes 5' capping, poly-A tail addition, and splicing.

Translation Requirements

Translation depends on the binding of ribosomal subunits and tRNA, while DNA does not directly participate.

Nucleotide Composition

If DNA has 30% cytosine, it will equally have 30% guanine due to complementary base pairing.

phiX174 Virus Structure

The phiX174 virus is characterized by single-stranded circular DNA.

Role of Introns

Introns contain termination codons but are removed before mRNA translation takes place.

Nucleotide Equivalence

In double-stranded DNA, A + C equals G + T due to base pairing rules.

RNA World Hypothesis

Proposes that early life forms used RNA as genetic material before DNA.

Pre-mRNA Processing Sequence

The sequence begins with transcription, followed by capping, recognition of AAUAAA by proteins, splicing, and export to the cytoplasm.

DNA Fragment Stability

Increased GC content in DNA fragments leads to higher stability against denaturation.

RNA Polymerase Functions

RNA Pol I synthesizes rRNA, RNA Pol II synthesizes mRNA and snRNA, and RNA Pol III synthesizes tRNA and rRNA.

Functions of the 5' Cap

The 5' cap facilitates ribosomal binding, protects RNA from degradation, and assists in intron removal.

Electrophoresis and Hemoglobin

Differences in charge allow separation of HbA from HbS in electrophoresis.

Polycistronic mRNA in Prokaryotes

Polycistronic mRNA carries coding information for multiple proteins.

Nucleotide Bonding

Covalent bonds form between 3' and 5' carbons of nucleotides during nucleic acid synthesis.

Antisense Oligonucleotides in Gene Therapy

Used to bind mRNA and inhibit gene expression related to genetic disorders.

RNA Characteristics

RNA has uracil instead of thymine, contains ribose sugar, is usually single-stranded, and is synthesized in the nucleus.

Nucleosome Composition

A nucleosome consists of DNA wrapped around histone proteins: H2A, H2B, H3, and H4.

Promoter Role in Transcription

RNA polymerase binds to a promoter region to initiate transcription.

Spliceosome Function

The spliceosome catalyzes the removal of introns from pre-mRNA.

tRNA Processing Location

tRNAs are transcribed in the nucleus but function in the cytoplasm.

Hershey-Chase DNA Evidence

DNA's phosphorus content was vital to demonstrate it as the genetic material.

Complementary DNA Pairing

A complementary DNA sequence can be derived from a given nucleotide strand.

Prokaryotic Ribosome Composition

Prokaryotic ribosomes consist of 16S, 5S, and 23S rRNA.

Anticodon Functionality

The tRNA anticodon pairs complementarily with mRNA during translation.

Result of Transcription

Transcribing a DNA sequence results in a specific RNA output.

Triplet Code Confirmation

Evidence from base addition or deletion experiments supports the triplet nature of the genetic code.

RNA Transcription Result

The RNA strand synthesized from a given DNA template follows base pairing rules.

Initiation Codon and Amino Acid

AUG serves as the initiator codon, recruiting methionine in both prokaryotes and eukaryotes.

Coupling in Prokaryotic Translation

In prokaryotes, translation occurs simultaneously with transcription.

Prokaryotic DNA Replication Properties

Prokaryotic DNA replication is characterized by a fixed point of initiation, bidirectionality, and being semiconservative.

Histone Composition and Function

Histones are rich in positively charged amino acids, aiding in the binding to negatively charged DNA and forming nucleosomes without H1.### DNA and Base Pairing
A DNA molecule with 50 base pairs containing 15 cytosine (C) bases has 35 thymine (T) bases.
In a DNA molecule that is 30% cytosine, the percentage of guanine (G) is also 30%.
DNA replication in vivo is described as semiconservative, meaning each new DNA molecule contains one original strand and one newly synthesized strand.

Protein Modifications and Genetic Material

Post-translational modifications of proteins can include the removal or alteration of terminal amino acids.
Hershey and Chase's experiment indicated that if phage ghosts contain a 32P label but lack it within infected E. coli, it suggests that protein serves as the genetic material for phage.

DNA Structure and Gene Regulation

A phosphate group is found at the 5' end of a DNA molecule.
DNA replication models include semiconservative, dispersive, and conservative approaches.
Enhancers are DNA sequences recognized by transcription factors; they act as control elements distant from the promoter and can be located far upstream or downstream of the gene they regulate.

Genetic Code and RNA Function

The genetic code shows redundancy; multiple codons can encode the same amino acid.
The genetic code is not ambiguous, ensuring that each codon codes for only one specific amino acid.
tRNA serves as the transporter of amino acids to the ribosome for protein synthesis.

Experimental Evidence and Gene Conservancy

Hairpins in DNA arise from inverted and complementary sequences within the same strand.
The one-gene, one-enzyme hypothesis developed from studies on Neurospora and Drosophila.
Exons (coding regions) of related genes are generally conserved across species, while introns (non-coding regions) show less conservation.

Ribosomes and RNA Types

Prokaryotic ribosomes consist of 16S rRNA, 5S rRNA, and 23S rRNA.
DNA primase synthesizes RNA primers necessary for DNA replication.
Amino acids build proteins, with tRNA transporting them for synthesis, and over 20 different amino acids are essential for bodily functions.

Functional RNAs and Genetic Material

Functional RNAs include:
- tRNA: brings amino acids during translation.
- rRNA: integral component of ribosomes.
- snRNA: processes RNA transcripts, particularly in intron removal.
Transformation refers to the genetic alteration of an organism by exposure to DNA, establishing that DNA is the genetic carrier.

Nucleotide Composition and Patterns

RNA comprises four nucleotides: adenine, guanine, cytosine, and uracil.
Observations indicate a pattern in the genetic code, where amino acids with similar chemical properties often share middle bases in codons.
Antiparallel orientation in DNA refers to the opposite directionality of the two strands, running 5' to 3'.

Miscellaneous Genetic Relationships

Relationships between DNA base percentages include:
- A + G = T + C (True)
- A + C = G + T (True)
- A + T / A + G = 1.0 (False)
Electrophoresis (gel electrophoresis) is a method for separating molecules based on their molecular charges.

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Description

Test your understanding of exon shuffling and autoradiography in this self-assessment quiz. The questions explore critical concepts that underpin molecular genetics and the experimental techniques used in the field. Perfect for students studying genetics in eukaryotes.