Nucleic Acids Overview and Structure
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Questions and Answers

DNA replication begins specifically at sites called origins of replication.

True

RNA is single-stranded and it contains the sugar ribose.

True

The two families of nitrogenous bases are ______ and ______.

  • Nucleosides and Nucleotides
  • Purines and Pyrimidines (correct)
  • Ribosomes and Proteins
  • DNA and RNA

    • How many nucleotides are necessary to code for a single amino acid?

    <p>3</p> Signup and view all the answers

    Which statement accurately describes the role of the template strand during transcription?

    <p>The template strand is always the same strand for a given gene.</p> Signup and view all the answers

    What are the building blocks of RNA transcripts during transcription?

    <p>Complementary nucleotides</p> Signup and view all the answers

    What term is used to refer to the segments of mRNA that are read during translation?

    <p>Codons</p> Signup and view all the answers

    What is the relationship between RNA processing and mRNA?

    <p>RNA processing modifies pre-mRNA to form mature mRNA.</p> Signup and view all the answers

    What is the significance of the antiparallel arrangement of the DNA strands?

    <p>It enables complementarity of base pairing during replication.</p> Signup and view all the answers

    Which pair of nitrogenous bases always bonds together in DNA?

    <p>Adenine (A) and Thymine (T)</p> Signup and view all the answers

    What role does each DNA strand play during replication?

    <p>Each strand acts as a template for building a new strand.</p> Signup and view all the answers

    How does the DNA molecule begin the replication process?

    <p>By unwinding at origins of replication.</p> Signup and view all the answers

    Which characteristic of the DNA double helix was proposed by Watson and Crick?

    <p>The specific base pairing suggests a copying mechanism.</p> Signup and view all the answers

    During DNA replication, what is the direction in which the new daughter strands are synthesized?

    <p>5' to 3' direction only</p> Signup and view all the answers

    What term describes the sites where DNA strands are separated during the initiation of replication?

    <p>Origins of replication</p> Signup and view all the answers

    What does the 'bubble' formed during DNA replication signify?

    <p>The separation of two strands of DNA.</p> Signup and view all the answers

    Why might eukaryotic chromosomes have multiple origins of replication?

    <p>To ensure rapid replication of large genomes.</p> Signup and view all the answers

    What is the primary function of hydrogen bonds in the structure of DNA?

    <p>To stabilize the DNA double helix structure.</p> Signup and view all the answers

    What is the complementary base sequence to AGCACT?

    <p>TCGTGA</p> Signup and view all the answers

    How does the structure of DNA contribute to its function?

    <p>It facilitates the transmission of genetic information during cell division.</p> Signup and view all the answers

    Which base pairs with adenine in RNA?

    <p>Uracil</p> Signup and view all the answers

    What role does hydrogen bonding play in DNA structure?

    <p>It holds the complementary base pairs together.</p> Signup and view all the answers

    When a cell reproduces, what happens to its DNA molecules?

    <p>They produce two identical copies for each daughter cell.</p> Signup and view all the answers

    Which statement about nucleotide pairing is correct?

    <p>Adenine pairs with thymine in DNA.</p> Signup and view all the answers

    What is a key characteristic of the base pairing rules in DNA?

    <p>They ensure accuracy in the transcription process.</p> Signup and view all the answers

    What distinguishes RNA from DNA in terms of nucleotide pairing?

    <p>RNA uses uracil instead of thymine to pair with adenine.</p> Signup and view all the answers

    What is the primary role of RNA in protein synthesis?

    <p>To act as a messenger between DNA and ribosomes.</p> Signup and view all the answers

    What type of sugar is found in DNA molecules?

    <p>Deoxyribose</p> Signup and view all the answers

    During DNA transcription, what is produced?

    <p>Messenger RNA (mRNA)</p> Signup and view all the answers

    Which of the following accurately describes the structure of DNA?

    <p>Double helix with complementary strands.</p> Signup and view all the answers

    What makes up a nucleotide?

    <p>A nitrogenous base, a sugar, and a phosphate group.</p> Signup and view all the answers

    What are the two types of nucleic acids?

    <p>DNA and RNA</p> Signup and view all the answers

    Which nitrogenous bases are classified as purines?

    <p>Adenine and Guanine</p> Signup and view all the answers

    In eukaryotic cells, where does the synthesis of mRNA occur?

    <p>In the nucleus</p> Signup and view all the answers

    What is the process of converting the information in mRNA into a polypeptide called?

    <p>Translation</p> Signup and view all the answers

    What connects adjacent nucleotides in a polynucleotide chain?

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

    What type of bond holds together the two strands of the DNA double helix?

    <p>Hydrogen bonds</p> Signup and view all the answers

    Which term describes the unique sequence of bases along a DNA or mRNA polymer?

    <p>Nucleotide sequence</p> Signup and view all the answers

    In which cellular location does translation occur in prokaryotic cells?

    <p>Cytoplasm</p> Signup and view all the answers

    What is the relationship between genes and the proteins they encode?

    <p>Genes encode instructions for protein synthesis.</p> Signup and view all the answers

    How does the genetic code ensure the proper synthesis of a polypeptide?

    <p>Codons must be read in the correct reading frame.</p> Signup and view all the answers

    What is true about the codons in mRNA?

    <p>Codons are composed of triplets of nucleotides.</p> Signup and view all the answers

    What is the primary role of ribosomes during translation?

    <p>To decode mRNA codons into amino acids.</p> Signup and view all the answers

    Which of the following statements about the genetic code is accurate?

    <p>It is redundant, allowing more than one codon to specify a single amino acid.</p> Signup and view all the answers

    During which stage of transcription does RNA polymerase bind to the DNA?

    <p>Initiation</p> Signup and view all the answers

    Which component is not part of the transcription process?

    <p>Ribosomes</p> Signup and view all the answers

    What is the function of stop codons?

    <p>To indicate the end of the polypeptide chain.</p> Signup and view all the answers

    In eukaryotic cells, what happens to pre-mRNA before it can be translated?

    <p>It undergoes a series of processing steps.</p> Signup and view all the answers

    What distinguishes the three stages of transcription?

    <p>The steps involving RNA polymerase activity.</p> Signup and view all the answers

    Which of the following describes the flow of genetic information?

    <p>Gene to protein via RNA.</p> Signup and view all the answers

    What is essential for the correct translation of mRNA into a polypeptide?

    <p>Codons must be sequenced in the correct order.</p> Signup and view all the answers

    What is the impact of redundancy in the genetic code?

    <p>It allows different codons to specify the same amino acid.</p> Signup and view all the answers

    What are codons made up of?

    <p>Triplets of nucleotides.</p> Signup and view all the answers

    What happens if codons are read incorrectly during translation?

    <p>A dysfunctional protein may be synthesized.</p> Signup and view all the answers

    What role does helicase play in DNA replication?

    <p>It unwinds the double helix at the replication forks.</p> Signup and view all the answers

    Why do DNA polymerases require a primer?

    <p>They cannot add nucleotides without a template strand.</p> Signup and view all the answers

    What is the function of primase in DNA replication?

    <p>It generates RNA primers to start new chains.</p> Signup and view all the answers

    In which direction can a new DNA strand elongate during replication?

    <p>From 5' to 3'</p> Signup and view all the answers

    What are Okazaki fragments?

    <p>Discontinuous segments of DNA synthesized on the lagging strand.</p> Signup and view all the answers

    What is the primary purpose of the sliding clamp during DNA replication?

    <p>To prevent DNA polymerase from dissociating from the strand.</p> Signup and view all the answers

    What happens to dATP during DNA strand elongation?

    <p>It loses two phosphate groups to form a monomer.</p> Signup and view all the answers

    How does topoisomerase contribute to DNA replication?

    <p>It correctly unwinds overtwisted DNA ahead of replication forks.</p> Signup and view all the answers

    Which of the following statements about the leading and lagging strands is accurate?

    <p>The leading strand is synthesized continuously toward the replication fork, whereas the lagging strand is away from it.</p> Signup and view all the answers

    Which component is essential for DNA polymerases to catalyze the elongation of new DNA strands?

    <p>A specific type of nucleoside triphosphate.</p> Signup and view all the answers

    What does the term 'antiparallel' refer to in the context of DNA strands?

    <p>The opposite orientation of the sugar-phosphate backbones.</p> Signup and view all the answers

    What is the function of single-strand binding proteins during DNA replication?

    <p>To stabilize unwound single-stranded DNA.</p> Signup and view all the answers

    Why is the rate of elongation different between bacteria and human cells?

    <p>Bacterial DNA polymerases are inherently faster than those in humans.</p> Signup and view all the answers

    Study Notes

    Nucleic Acids: Overview

    • Nucleic acids store and transmit hereditary information
    • Two types: DNA and RNA

    DNA Structure

    • Double helix structure
    • Two strands are antiparallel
    • Bases pair: Adenine (A) with Thymine (T), Guanine (G) with Cytosine (C)
    • Complementary base pairing allows DNA replication

    The Roles of Nucleic Acids

    • DNA provides instructions for its own replication
    • DNA directs the synthesis of mRNA (messenger RNA)
    • mRNA controls protein synthesis
    • Protein synthesis occurs in ribosomes

    Nucleotide Monomers

    • Two families of nitrogenous bases: pyrimidines (cytosine, thymine, uracil) and purines (adenine, guanine)
    • Pyrimidines have a single six-membered ring
    • Purines have a six-membered ring fused to a five-membered ring
    • Sugar is deoxyribose in DNA and ribose in RNA

    Nucleotide Polymers

    • Nucleic acids are polymers called polynucleotides
    • Each polynucleotide is made of monomers called nucleotides
    • Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
    • The portion without the phosphate group is called a nucleoside

    DNA Replication: Overview

    • Replication occurs at origins of replication, creating replication bubbles
    • Replication proceeds in both directions from each origin
    • DNA polymerases catalyze DNA synthesis
    • Require a primer and a DNA template strand
    • Elongation is 5' to 3'
    • Strands are antiparallel
    • Leading strand is synthesized continuously
    • Lagging strand is synthesized in Okazaki fragments, joined by DNA ligase

    DNA Replication: Enzymes

    • Helicases untwist the double helix
    • Single-strand binding proteins stabilize single strands
    • Topoisomerase corrects overwinding
    • Primase synthesizes RNA primers
    • DNA polymerase III adds nucleotides to the 3' end
    • DNA polymerase I replaces RNA primers with DNA
    • DNA ligase joins Okazaki fragments

    DNA Replication Proofreading and Repair

    • DNA polymerases proofread newly made DNA
    • Mismatch repair corrects errors in base pairing
    • Nucleotide excision repair removes damaged DNA stretches

    Eukaryotic Chromosomes

    • DNA molecules are linear
    • Have telomeres at ends
    • Telomeres postpone the erosion of genes near the ends
    • Telomerase catalyzes the lengthening of telomeres in germ cells

    Chromatin Structure

    • Chromatin is DNA and protein complex
    • First level of packing is nucleosomes
    • Nucleosomes form a 30-nm fiber
    • Looped domains form a 300-nm fiber
    • A mitotic chromosome is a highly compacted structure

    Gene Expression

    • Gene expression includes transcription and translation
    • Transcription produces mRNA from DNA
    • Translation produces proteins from mRNA

    The Genetic Code

    • Codons are three-nucleotide words
    • The genetic code is nearly universal, translating the same codons into the same amino acids in various organisms.
    • Redundant (multiple codons for one amino acid) but not ambiguous

    Transcription

    • RNA polymerase pries the DNA strands apart
    • RNA synthesis follows the base pairing rules (U substitutes for T)
    • The promoter signals the transcriptional start point
    • Transcription unit is the DNA sequence that is transcribed
    • Initiation, elongation, and termination are three stages of transcription

    Eukaryotic RNA Processing

    • Pre-mRNA is modified before leaving the nucleus
    • 5' end receives a 5' cap
    • 3' end gets a poly-A tail
    • Introns are removed by splicing
    • Spliceosomes carry out the splicing of introns

    Translation

    • mRNA specifies the amino acid sequence
    • Ribosomes translate mRNA into amino acid sequence
    • tRNA molecules carry amino acids to the ribosome during translation
    • rRNA are components of ribosomes

    Protein Synthesis: Overview

    • Initiation, elongation, and termination are three stages in protein synthesis.
    • Initiation brings together mRNA, tRNA (carrying the first amino acid), and the two ribosomal subunits

    Post-Translation Modification

    • Polypeptide chain folds into 3D shape
    • Post-translational modifications can activate or modify protein function

    Mutations: Overview

    • Mutations are changes in the genetic material
    • Small-scale mutations (point mutations) are changes in one or a few base pairs
    • Substitutions, insertion, and deletion can occur

    Types of Mutations (Small-Scale)

    • Substitutions include silent, missense, and nonsense mutations
    • Insertions and deletions can cause frameshift mutations

    Cancer and Gene Regulation

    • Cancer results from mutations affecting cell cycle control
    • Oncogenes are cancer-causing genes, while proto-oncogenes are normal genes that control cell growth
    • Tumor-suppressor genes encode proteins that inhibit cell division

    Other Mechanisms for Gene Regulation

    • DNA methylation, chromatin modifying enzymes, activators and repressors, RNA processing, RNA interference, protein processing and degradation, mRNA degradation, and initiation of translation.

    Cancer Resulting from Genetic Changes

    • Cancer is caused by accumulated mutations in proto-oncogenes and tumor suppressor genes.
    • Oncogenes, when mutated, promote excessive cell division.
    • Tumor suppressor genes, when mutated, fail to inhibit abnormal cell division.
    • Viruses can contribute to cancer by integrating viral DNA into a cell's genome.
    • Mutations in genes regulating cell growth and division contribute to cancer development.

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    DNA Structure & Replication PDF

    Description

    Explore the essential roles and structures of nucleic acids in heredity and protein synthesis in this quiz. Learn about the double helix of DNA, nucleotide monomers, and the critical functions of DNA and RNA in organisms. Test your understanding of these fundamental biological molecules!

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