Introduction to Molecular Biology 1
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Questions and Answers

In which decade was the term 'molecular biology' first introduced?

  • 1930s (correct)
  • 1940s
  • 1920s
  • 1950s

    • What significant discovery did Erwin Chargaff make in 1950 regarding DNA?

  • The primary structure of DNA
  • The existence of messenger RNA
  • Equivalence in the ratios of adenine to thymine and guanine to cytosine (correct)
  • The double helix structure

    • Which scientists are credited with discovering the double helical structure of DNA?

  • James Watson and Rosalind Franklin
  • Erwin Chargaff and Francis Crick
  • Francis Crick and Erwin Chargaff
  • James Watson and Francis Crick (correct)

    • Which molecule serves as an intermediary between DNA and proteins?

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

    What is the central dogma of molecular biology?

    <p>DNA -&gt; RNA -&gt; Protein</p> Signup and view all the answers

    Who is credited with the discovery of uracil in the early 20th century?

    <p>Dr. Phoebus Levene</p> Signup and view all the answers

    What key aspect of DNA was revealed by understanding its primary structure?

    <p>The secondary structure formation</p> Signup and view all the answers

    Which of the following components is NOT a nitrogen base found in DNA?

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

    What property of DNA contributes to its hydrophilic nature?

    <p>Presence of phosphate groups</p> Signup and view all the answers

    At what wavelength do DNA bases absorb ultraviolet light most effectively?

    <p>260 nanometers</p> Signup and view all the answers

    What happens to DNA during denaturation?

    <p>DNA double strand unwinds</p> Signup and view all the answers

    Which base pairing contributes to a higher melting temperature in DNA?

    <p>C-G pairs due to three hydrogen bonds</p> Signup and view all the answers

    What is the overall electrical charge of DNA?

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

    What temperature condition is necessary for DNA to denature?

    <p>High temperature</p> Signup and view all the answers

    When does the process of renaturation occur in DNA?

    <p>When temperature is decreased</p> Signup and view all the answers

    What does the melting temperature of DNA indicate?

    <p>Half of the DNA molecule is denatured</p> Signup and view all the answers

    What configuration does the nucleic backbone primarily consist of?

    <p>Alternating phosphate and sugar</p> Signup and view all the answers

    Which position on the sugar molecule is important for attaching to phosphate?

    <p>3’ and 5’</p> Signup and view all the answers

    Which of the following groups makes DNA negatively charged?

    <p>Phosphate groups</p> Signup and view all the answers

    What is the major difference between a nucleoside and a nucleotide?

    <p>Nucleotide has phosphate</p> Signup and view all the answers

    What is the direction of the Watson strand in DNA?

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

    What are the characteristics of the major and minor grooves in DNA?

    <p>Major: deep and wide; Minor: narrow and shallow</p> Signup and view all the answers

    At what wavelength does DNA absorb light most effectively?

    <p>260 nm</p> Signup and view all the answers

    What is the primary role of phosphodiester bonds in DNA?

    <p>Forming the backbone of DNA</p> Signup and view all the answers

    What is the primary function of DNA?

    <p>To store and pass on genetic information</p> Signup and view all the answers

    How is the structure of DNA commonly described?

    <p>In a spiral staircase or twisted ladder shape</p> Signup and view all the answers

    Which three components make up DNA?

    <p>Deoxyribose, phosphate, nitrogenous bases</p> Signup and view all the answers

    What distinguishes deoxyribose from ribose?

    <p>Deoxyribose lacks a hydroxyl group at carbon 2’</p> Signup and view all the answers

    What is the chemical composition of a phosphate molecule?

    <p>One phosphorus and four oxygen atoms</p> Signup and view all the answers

    What is the composition of the DNA backbone?

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

    What type of sugar is ribose classified as?

    <p>Pentose sugar</p> Signup and view all the answers

    In the context of DNA directionality, what is the significance of carbon numbering?

    <p>It is key for describing the directionality of DNA</p> Signup and view all the answers

    Which type of bond links the sugars and phosphate groups in the DNA backbone?

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

    Which specific carbon atoms are involved in linking the hydroxyl groups to phosphate groups?

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

    Which of the following correctly describes the relationship between ribose and RNA?

    <p>Ribose is a pentose sugar found in RNA</p> Signup and view all the answers

    What makes up the steps of the DNA ladder?

    <p>Pairs of nitrogenous bases</p> Signup and view all the answers

    Which of the following nitrogenous bases is NOT found in DNA?

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

    What type of bond primarily forms the rails of the DNA ladder?

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

    How do the nitrogenous bases pair in DNA?

    <p>Thymine with Adenine</p> Signup and view all the answers

    Which structural component is absent in the DNA backbone?

    <p>Nitrogenous bases</p> Signup and view all the answers

    What did Erwin Chargaff discover about the ratios of nucleotides in DNA?

    <p>Adenine percentage equals thymine percentage, and guanine percentage equals cytosine percentage.</p> Signup and view all the answers

    Which of the following statements accurately reflects the conclusions drawn from Rosalind Franklin's X-ray diffraction work?

    <p>DNA is a helical structure with a consistent width.</p> Signup and view all the answers

    How did Watson and Crick use Chargaff's discoveries in their model of DNA?

    <p>They arranged nucleotides with complementary base pairing.</p> Signup and view all the answers

    Which year did Erwin Chargaff begin his comparative studies on nucleotides?

    <p>1949</p> Signup and view all the answers

    What is one of the crucial features of the DNA double helix suggested by Watson and Crick?

    <p>The structure is stabilized by hydrogen bonds between opposite bases.</p> Signup and view all the answers

    Which of the following organisms had the same percentage of adenine and thymine as human DNA, according to Chargaff's findings?

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

    Which of the following correctly identifies a key observation made through Chargaff's research?

    <p>The ratios of certain nucleotides are equal across many species.</p> Signup and view all the answers

    How did Watson and Crick demonstrate base pairing in DNA?

    <p>By using Chargaff's rule to pair nucleotides together.</p> Signup and view all the answers

    Study Notes

    Introduction to Molecular Biology 1

    • This course covers cell biology and molecular biology (CM1)
    • The module is part of a Molecular Biology course
    • The course was given on October 26th, 2024
    • The academic year is 2024-2025

    Course Contents

    • Objective of the course: Not specified
    • Central Dogma of molecular biology: A theory stating that genetic information flows from DNA to RNA to protein, or RNA directly to protein.
    • DNA discovery: DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher (called nuclein). The term "molecular biology" was introduced in 1938 by Warren Weaver
    • DNA composition: DNA is made of deoxyribose, phosphate, and nitrogenous bases (adenine, cytosine, guanine, thymine)
    • DNA backbone: Ester bonds, or phosphodiester bonds, form the DNA backbone, joining deoxyribose and phosphate.
    • Physical and Chemical Properties of DNA:
      • Solubility: DNA is soluble in water due to its charged phosphate backbone; however, it is insoluble in salt and alcohol.
      • Absorption: DNA bases absorb ultraviolet light at 260 nm.
      • Denaturation and Renaturation: High temperature or extreme pH can cause DNA to denature (separate into single strands). Cooling allows strands to renature (reform into a double helix). The melting temperature varies by DNA sequence.
      • DNA electrical charge: DNA is negatively charged due to the negatively charged phosphate groups.
      • DNA packaging: DNA is packaged inside microscopic nuclei with the help of histones

    Mitochondria DNA

    • Mitochondria are the main source of ATP
    • Mitochondrial DNA is a ~16 kb circular molecule
    • Mitochondrial DNA contains 37 genes:
      • 2 for rRNAs
      • 22 for tRNAs and mRNAs
      • 13 for proteins used for oxidative processes
    • Each human cell has approximately 100 mitochondria
    • Each mitochondrion has 2 to 10 copies of mtDNA
    • mtDNA replicates independently

    Bacterial DNA

    • Bacterial DNA is found loose in the cytoplasm. It's not contained within a nucleus
    • A plasmid is a small, extrachromosomal DNA molecule that replicates independently.

    DNA in Eukaryotes and Prokaryotes

    • In Eukaryotic cells, DNA is housed within a nucleus and bound to proteins (histones)
    • Eukaryotic DNA is linear and usually contains introns
    • In Prokaryotic cells, DNA is within the cytoplasm and naked (not bound to protein)
    • Prokaryotic DNA is circular and usually without introns

    Molecular Biology History

    • 1950: Erwin Chargaff discovered that the ratios of adenine to thymine (A:T), and guanine to cytosine (G:C) are equal in DNA
    • 1953: James Watson and Francis Crick discovered the DNA double helix structure.
    • 1961: Francois Jacob and Jacques Monod discovered messenger RNA.
    • 1961: Crick et al. published a paper deciphering the triplet codon pattern

    Learning Objectives and Course Organization

    • The lecture will cover important dates and describe the structure, composition, and characteristics of DNA and RNA

    Introduction

    • Molecular biology studies macromolecules and their mechanisms in living organisms
    • It focuses on how molecules interact to carry out life functions, including gene mechanisms, replication, mutation and gene expression.

    Central Dogma of Molecular Biology

    • Genetic information flows from DNA to RNA to protein, or RNA directly to protein.
    • A dogma is an established opinion

    The Nobel Prize

    • The Nobel Prize in Physiology/Medicine in 1962 was awarded to James Watson, Francis Crick, and Maurice Wilkins for their discovery of the DNA molecular structure
    • Rosalind Franklin was not awarded the prize
    • James Watson sold his DNA co-discoverer's Nobel Prize medal for US$4.7 million in 2014

    Quiz Questions

    • Various quiz questions covering different DNA concepts (composition, structure, function, and history).

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    Introduction to Molecular Biology 1 PDF

    Description

    Dive into the foundational concepts of molecular biology with this quiz. Explore key topics such as the Central Dogma, DNA composition, and its discovery. Test your knowledge and understand the physical and chemical properties of DNA.

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