Molecular Biology: Nucleic Acids Quiz
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Questions and Answers

How does DNA polymerase contribute to the accuracy of DNA replication?

  • By copying both strands of DNA simultaneously
  • By proofreading each nucleotide addition (correct)
  • By adding nucleotides without checking them
  • By creating RNA primers before replication

What distinguishes transcription from DNA replication?

  • A single strand of DNA serves as a template in transcription (correct)
  • Transcription uses DNA polymerase to synthesize RNA
  • Both strands of DNA are copied in transcription
  • Transcription occurs inside the nucleus while replication does not

What are the main chemical constituents found in nucleic acids?

  • Sugars, amino acids, and sterols
  • Vitamins, carbohydrates, and lipids
  • Proteins, fatty acids, and nucleotides
  • Nitrogenous bases, pentose sugar, and phosphate (correct)

What do codons represent in the genetic code?

<p>Blocks of three nucleotides that specify amino acids (C)</p> Signup and view all the answers

How are tRNA molecules involved in translation?

<p>They bring amino acids and match codons on the mRNA (A)</p> Signup and view all the answers

Which sugar is found in RNA?

<p>Ribose (B)</p> Signup and view all the answers

What is the conformation of Z-DNA?

<p>Left-handed helix (A)</p> Signup and view all the answers

What is released during the formation of a polynucleotide chain from nucleotides?

<p>Pyrophosphate (A)</p> Signup and view all the answers

What is the function of ultraviolet absorption at 260 nm in the context of nucleic acids?

<p>To measure nucleic acid concentrations (A)</p> Signup and view all the answers

Which of the following statements about the stability of nucleic acids is true?

<p>Nucleic acids are thermodynamically favored to break down slowly. (B)</p> Signup and view all the answers

What type of bases are derivatives of purines and pyrimidines found in nucleic acids?

<p>Nucleotides (C)</p> Signup and view all the answers

Which component is included in a nucleotide but not in a nucleoside?

<p>Phosphate (D)</p> Signup and view all the answers

What is primarily responsible for making the reaction thermodynamically favorable in nucleic acid processes?

<p>Cleavage of the NTP (B)</p> Signup and view all the answers

Which statement correctly describes the directionality of a polynucleotide chain?

<p>One end has an unreacted hydroxyl group, and the other has an unreacted phosphate (A)</p> Signup and view all the answers

What does the primary structure of nucleic acids refer to?

<p>The sequence of its bases (D)</p> Signup and view all the answers

What indicates the type of nucleic acid when a sequence includes the letter T?

<p>It signals a DNA sequence (A)</p> Signup and view all the answers

In shorthand notation for nucleic acids, what does the notation 'ACGTT' represent?

<p>A specific DNA sequence (D)</p> Signup and view all the answers

What is the main importance of a DNA sequence?

<p>It stores genetic information (B)</p> Signup and view all the answers

What was the contribution of Avery et al. to our understanding of DNA?

<p>They demonstrated DNA's role as the genetic material (A)</p> Signup and view all the answers

How did Hershey and Chase's experiments demonstrate DNA as the genetic material?

<p>By showing the transfer of viral DNA to bacteria (D)</p> Signup and view all the answers

What is the relationship between genes and primary structure in DNA?

<p>Genes represent specific sequences of nucleotides (D)</p> Signup and view all the answers

What type of supercoiling is predominantly found in most DNA molecules in vivo?

<p>Left-handed supercoiling (C)</p> Signup and view all the answers

Which of the following best describes the random coil structure of denatured single strands of nucleic acids?

<p>Flexible with rotation of residues and no specific structure (B)</p> Signup and view all the answers

What are the high-order folding patterns of secondary structures in DNA referred to as?

<p>Tertiary structures (A)</p> Signup and view all the answers

Which enzyme complex is responsible for the replication of DNA?

<p>Replisome (C)</p> Signup and view all the answers

Which statement about DNA polymerase is true?

<p>It guides the pairing of dNTPs with their complementary partners. (D)</p> Signup and view all the answers

What comprises an organism's genome?

<p>At least one copy of the total genetic information (B)</p> Signup and view all the answers

What is a characteristic feature of RNA molecules under native conditions?

<p>They form hairpin structures due to self-complementarity. (C)</p> Signup and view all the answers

How large is the human genome approximately?

<p>1 x 10^9 bp (C)</p> Signup and view all the answers

What happens to parental DNA strands during DNA replication?

<p>They unwind to form a replication fork. (C)</p> Signup and view all the answers

Which structure is the primary structure of DNA or RNA primarily held together by?

<p>Covalent bonds (B)</p> Signup and view all the answers

What type of bonding occurs between A-T base pairs in DNA?

<p>Two hydrogen bonds (D)</p> Signup and view all the answers

Which form of DNA is most commonly found in biological systems?

<p>B form (B)</p> Signup and view all the answers

What does the rise of the helix refer to in DNA structure?

<p>The distance between base pairs (A)</p> Signup and view all the answers

What model of DNA replication is supported by the Meselson–Stahl experiment?

<p>Semiconservative model (C)</p> Signup and view all the answers

Which type of nucleic acid structure is characterized by a 2' hydroxyl group that prevents it from adopting a B form?

<p>Double-stranded RNA (D)</p> Signup and view all the answers

How does the base pairing mechanism in DNA facilitate genetic replication?

<p>By using both strands as templates (D)</p> Signup and view all the answers

What is a significant feature of the Watson-Crick model of DNA?

<p>It describes base pairing between keto tautomers (B)</p> Signup and view all the answers

Which characteristic is true for supercoiled DNA?

<p>Can compact DNA further for storage (D)</p> Signup and view all the answers

What is a major difference in the structural properties of A form and B form DNA?

<p>B form is the most stable form in aqueous environments (B)</p> Signup and view all the answers

What observable feature indicates a DNA molecule's degree of supercoiling?

<p>Shape variance of DNA in different conditions (D)</p> Signup and view all the answers

Flashcards

Nucleotides

The building blocks of nucleic acids, composed of a nitrogenous base, a pentose sugar, and a phosphate group.

Deoxyribose

The sugar component of DNA, lacking a hydroxyl group at the 2' position.

Ribose

The sugar component of RNA, containing a hydroxyl group at the 2' position.

Nucleotide addition to a polynucleotide

The process of adding a nucleotide to a growing polynucleotide chain, where a nucleoside triphosphate (like ATP or dATP) is used as the source of the nucleotide.

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Pyrophosphate hydrolysis in nucleotide addition

This is the main driving force behind the polymerization reaction, as the energy released by pyrophosphate hydrolysis favors the formation of the phosphodiester bond.

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Phosphodiester bond

The bond that links nucleotides together in a polynucleotide chain, formed between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next.

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Primary Structure of Nucleic Acids

The sequence of nucleotides that makes up a polynucleotide chain.

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NTP Cleavage

The energy released when a nucleoside triphosphate (NTP) is broken down, used to drive the formation of phosphodiester bonds in nucleic acid synthesis.

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Polymerases

Enzymes responsible for synthesizing nucleic acids like DNA and RNA by linking nucleotides together.

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Directionality of Nucleic Acids

A polynucleotide chain has a defined directionality due to the asymmetric phosphodiester linkage, with a 5' end and a 3' end.

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5' End

The 5' end of a nucleic acid chain is characterized by a free phosphate group.

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3' End

The 3' end of a nucleic acid chain is characterized by a free hydroxyl group.

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Nucleotide Sequence

The unique sequence of nucleotides in a nucleic acid molecule, determining its specific function.

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Avery et al. Experiment

The experiment by Avery et al. demonstrated that DNA is responsible for transferring genetic information from pathogenic to nonpathogenic strains of bacteria.

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Hershey-Chase Experiment

The Hershey-Chase experiment confirmed that DNA is the genetic material, not protein, by showing that viral DNA is transferred and responsible for new virus production.

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DNA Polymerase Function

DNA polymerase adds nucleotides to a growing daughter strand, ensuring accuracy by proofreading each addition.

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Leading and Lagging Strands

The two DNA strands run in opposite directions, so one daughter strand is extended continuously while the other is synthesized in small fragments.

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Transcription Process

DNA is transcribed into RNA using ribonucleoside triphosphates (ATP, GTP, CTP, and UTP) and only one DNA strand (template strand) is copied.

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Genetic Code

The genetic code is a set of rules that determines which amino acid corresponds to each three-nucleotide codon on mRNA.

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mRNA Function

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes where it is translated into a protein.

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Secondary Structure of Nucleic Acids

The regular folding patterns observed in DNA double helices, stabilized by non-covalent hydrogen bonds. Examples include A-DNA and B-DNA.

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Tertiary Structure of Nucleic Acids

The three-dimensional arrangement of the folded DNA double helix, involving interactions between the secondary structures.

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Supercoiled DNA

DNA molecules that are wound tighter than their relaxed state, typically found in living organisms.

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DNA Replication

The process of copying both strands of a DNA duplex to produce two identical DNA duplexes.

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Replisome

A group of enzymes that work together to carry out DNA replication.

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DNA Polymerase

An enzyme that adds nucleotides to a growing DNA chain during replication, pairing them with their complementary bases.

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Replication Fork

A Y-shaped structure formed during DNA replication where the parental strands are unwound, allowing new DNA to be synthesized.

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Genome

The complete set of genetic information carried by an organism, usually encoded in DNA.

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Hairpin Structure

A single-stranded nucleic acid molecule that folds back on itself to form a stem-loop structure, often found in RNA.

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What are the base pairs in DNA?

In Watson-Crick DNA model, adenine (A) pairs with thymine (T) via two hydrogen bonds, while guanine (G) pairs with cytosine (C) via three hydrogen bonds.

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How does DNA structure enable replication?

The double-stranded structure of DNA explains how the genetic information is copied during replication, with each strand acting as a template for a new complementary strand.

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What is the rise of the DNA helix?

The distance between two adjacent base pairs in a DNA helix is 0.34 nm.

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What are the main forms of DNA and RNA?

DNA exists in two major forms, A and B, with most DNA being in the B form. Double-stranded RNA and DNA-RNA hybrids adopt the A form due to the presence of the 2' hydroxyl group in RNA preventing it from adopting the B form.

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What is DNA supercoiling?

Supercoiling is a process where the DNA helix twists upon itself, leading to either under-winding or over-winding. It can be relaxed or supercoiled, and influences DNA's compactness and accessibility.

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What did the Meselson-Stahl experiment show about DNA replication?

The Meselson-Stahl experiment proved that DNA replication is semiconservative, meaning that each daughter DNA molecule contains one original strand and one newly synthesized strand.

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What is the primary structure of DNA?

DNA is made of nucleotides linked together by phosphodiester bonds, forming a long chain. The sequence of nucleotides determines the genetic information.

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How are base pairs arranged in DNA?

The base pairs in DNA are stacked on top of each other, with each pair rotated 36° relative to the next. This stacking contributes to the stability of the double helix.

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What are the grooves in DNA?

The grooves in the DNA double helix are formed by the uneven distribution of the sugar-phosphate backbone. There are two grooves - the major groove and the minor groove.

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How diverse is DNA structure?

DNA molecules vary in length, ranging from thousands to millions of base pairs. They can also be linear or circular, and can exist in relaxed or supercoiled states. These variations affect their function and packaging in the cell.

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Study Notes

Biochemistry I - CHM219

  • The course is Biochemistry I, CHM219, taught by Dr. Esra Aydemir
  • Nucleic acids are a primary focus
  • Nucleic acids are the principal organic constituents of cells and organisms along with proteins, carbohydrates, and lipids
  • Nucleic acids are important for storage and transmission of biological information
  • Chemically, nucleic acids consist of organic nitrogenous bases, a pentose sugar, and phosphate
  • DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are two types of nucleic acids, differing in the sugar component.
  • RNA contains the sugar ribose.
  • DNA has deoxyribose.
  • Both DNA and RNA are polynucleotides.

Nucleic Acid Structure

  • The two types of heterocyclic bases (purines and pyrimidines) are derivatives of purine and pyrimidine
  • Purines include adenine (A), guanine (G)
  • Pyrimidines include cytosine (C), thymine (T), and uracil (U)
  • Nucleosides are a nitrogenous base with a ribose
  • Nucleotides are a nitrogenous base, a ribose, and a phosphate
  • G, T, and U can partially tautomerize to enol forms.
  • A and C tautomerize to imino forms.

Nucleic Acid Function

  • UV absorption spectra of ribonucleotides (GMP, AMP, UMP, CMP) are used to measure nucleic acid concentrations
  • Nucleic acids are metastable compounds favored to break down but take a long time unless catalyzed
  • The nucleoside triphosphate is added to the growing chain
  • The reaction is further favored by the hydrolysis of pyrophosphate to orthophosphate (inorganic phosphate (P₁))

DNA Replication

  • DNA replication is the copying of both strands of a DNA duplex to produce two identical DNA duplexes
  • DNA replication is accomplished by a complex of enzymes called the replisome
  • Each strand acts as a template for a new, complementary strand
  • When complete, there are two double-stranded daughter DNA molecules, each identical in sequence to the parent molecule
  • Experimental evidence supports the semiconservative model.

DNA Structure

  • The structure of B-DNA is based on molecular crystal studies.
  • Local distortions exist and DNA molecules in nature can be slightly bent from the vertical axis.
  • DNA in cells can vary in size and shape
  • DNA can be circular or linear
  • DNA can be relaxed or supercoiled

DNA Structure (Secondary and Tertiary)

  • A and B are the secondary structures of nucleic acids (DNA)
  • B DNA molecules have major and minor grooves
  • Some DNA is in a Z conformation, a left handed helix with alternate purine/pyrimidine bases in a syn/anti conformation. Purines are syn, and pyrimidines are anti.
  • DNA denaturation occurs when the double stranded DNA molecule separates into its single strands when heated over its melting temperature (Tm)

Manipulating DNA

  • Recombinant DNA techniques study nucleic acids and their translation into proteins
  • Recombinant DNA techniques include: Gene cloning, Chemical synthesis of oligonucleotides, DNA sequence analysis, Site-directed mutagenesis, Polymerase chain reaction (PCR)
  • pBR322 is an example of an early cloning vector
  • Techniques exist for chemical synthesis of oligonucleotides
  • Sanger developed a method for DNA sequencing using 2',3'-dideoxynucelotides

Transcription and Translation

  • Transcription is the copying of a DNA strand into a complementary RNA molecule
  • Contrast to DNA replication, transcription uses ribonucleoside triphosphates (ATP, GTP, CTP, and UTP) rather than deoxyribonucleotide triphosphates to synthesize RNA
  • Only one of the two DNA strands is copied
  • The linear sequence of bases constitutes the protein-coding information in blocks of three nucleotide residues (codons)
  • mRNA is transcribed from DNA; mRNA is translated into amino acid sequences

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Biochemistry I CHM219 Fall 2021 Lecture Notes PDF

Description

Test your knowledge on the fundamental concepts of nucleic acids, including DNA replication, transcription, and translation processes. This quiz covers key components such as codons, nucleotide structure, and the role of various molecules in genetic information processing.

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