Central Dogma and Key Experiments in DNA
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Questions and Answers

What is the key difference between microevolution and macroevolution?

  • Microevolution is a term used for genetic variations, while macroevolution is about physical changes in organisms.
  • Microevolution occurs only over short time scales, whereas macroevolution takes place over millions of years.
  • Microevolution focuses on changes within a species, while macroevolution involves the emergence of new species. (correct)
  • Microevolution deals with ecological interactions, while macroevolution is focused on reproductive isolation.

    • Which of the following is NOT considered a type of prezygotic reproductive barrier?

  • Mechanical isolation
  • Behavioral isolation
  • Temporal isolation
  • Hybrid inviability (correct)

    • In the context of the biological species concept, which aspect is crucial for defining a species?

  • Genetic variation within a population
  • Ecological roles in their environment
  • Morphological similarities
  • Reproductive isolation among populations (correct)

    • What distinguishes allopatric speciation from sympatric speciation?

    <p>Allopatric speciation occurs due to geographical separation, while sympatric speciation occurs without physical barriers.</p> Signup and view all the answers

    Which statement best describes the concept of hybrid zones in evolutionary biology?

    <p>Hybrid zones are areas where two species mate and produce viable offspring.</p> Signup and view all the answers

    What is the Central Dogma of Molecular Biology?

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

    What did the Griffith Experiment demonstrate?

    <p>Genetic material can be transferred between bacteria.</p> Signup and view all the answers

    What significance did the Hershey & Chase Experiment have?

    <p>Demonstrated DNA is the genetic material in viruses.</p> Signup and view all the answers

    What do Chargaff’s Rules state?

    <p>A = T and G = C</p> Signup and view all the answers

    What is the function of helicase during DNA replication?

    <p>To unwind the double helix of DNA.</p> Signup and view all the answers

    During DNA synthesis, in which direction does DNA polymerase synthesize the daughter strand?

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

    What is a key difference between DNA polymerase III and DNA polymerase I in E.coli?

    <p>DNA polymerase III synthesizes new DNA strands, while DNA polymerase I removes RNA primers.</p> Signup and view all the answers

    What does the term 'virulent' refer to in the context of the Griffith Experiment?

    <p>The organism's capability to cause disease.</p> Signup and view all the answers

    What is the role of the E.coli mismatch repair system when DNA is damaged by ultraviolet light?

    <p>To correct misincorporated bases</p> Signup and view all the answers

    What is the genetic code described as being 'degenerate'?

    <p>There are multiple codons for the same amino acid</p> Signup and view all the answers

    Which of the following best defines a gene?

    <p>A segment of DNA that codes for a protein or RNA</p> Signup and view all the answers

    What is one primary purpose of dideoxyribonucleotide triphosphates (ddNTPs) during DNA sequencing?

    <p>To terminate DNA synthesis at specific nucleotides</p> Signup and view all the answers

    Which of the following describes how natural selection fosters evolution?

    <p>By allowing certain traits to become more common in a population over generations</p> Signup and view all the answers

    What is the basis of the Hardy-Weinberg principle?

    <p>Defining the conditions for genetic equilibrium</p> Signup and view all the answers

    What process converts pre-mRNA into mature mRNA in eukaryotic cells?

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

    What does it mean if an organism is homozygous for a trait?

    <p>It carries two identical alleles for the trait</p> Signup and view all the answers

    Which component of the ribosome is responsible for holding tRNA and growing polypeptides together?

    <p>P site</p> Signup and view all the answers

    What is the primary effect of the bottleneck effect on a population's genetic diversity?

    <p>It diminishes diversity drastically</p> Signup and view all the answers

    In molecular biology, which evidence supports the theory of evolution by showing shared ancestry among different species?

    <p>Homologous structures</p> Signup and view all the answers

    What is a characteristic of the transfer RNA (tRNA) molecule?

    <p>It carries amino acids to the growing polypeptide chain</p> Signup and view all the answers

    What is the main purpose of performing PCR (Polymerase Chain Reaction)?

    <p>To amplify specific regions of DNA</p> Signup and view all the answers

    What are exons in eukaryotic genes?

    <p>Coding sequences that remain in mRNA</p> Signup and view all the answers

    What does the term 'transformation' refer to in the context of the Griffith Experiment?

    <p>The genetic alteration of a cell resulting from the uptake of external DNA</p> Signup and view all the answers

    Which of the following describes Chargaff’s Rules?

    <p>The amount of adenine equals the amount of thymine, and the amount of cytosine equals the amount of guanine</p> Signup and view all the answers

    What is the significance of Rosalind Franklin's Photo 51?

    <p>It provided evidence of the helical structure of DNA</p> Signup and view all the answers

    What did the Meselson & Stahl Experiment demonstrate about DNA replication?

    <p>DNA replication is a semiconservative process</p> Signup and view all the answers

    Which enzyme is responsible for unwinding the DNA double helix during replication?

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

    What is the role of DNA polymerase I in E.coli?

    <p>It removes RNA primers and replaces them with DNA</p> Signup and view all the answers

    What type of DNA strand is synthesized continuously during replication?

    <p>Leading strand</p> Signup and view all the answers

    How do deoxyribonucleotide triphosphates (dNTPs) function during DNA replication?

    <p>They act as building blocks for DNA synthesis</p> Signup and view all the answers

    Which of the following best describes the '5' and 3' ends of DNA?

    <p>They denote the antiparallel nature of DNA strands</p> Signup and view all the answers

    What does it mean for a bacterium to be virulent?

    <p>It causes disease or harm to a host organism</p> Signup and view all the answers

    What is speciation?

    <p>The generation of new and distinct species.</p> Signup and view all the answers

    How do the morphological and ecological species concepts differ?

    <p>Morphological focuses on physical traits, while ecological focuses on environmental interactions.</p> Signup and view all the answers

    Which of the following is NOT a type of prezygotic reproductive barrier?

    <p>Hybrid inviability</p> Signup and view all the answers

    What are the two main types of postzygotic barriers?

    <p>Hybrid sterility and hybrid inviability</p> Signup and view all the answers

    Which mechanism describes the formation of new species due to geographical separation?

    <p>Allopatric speciation</p> Signup and view all the answers

    Which concept best describes areas where two different species meet and reproduce, leading to hybrid offspring?

    <p>Hybrid zones</p> Signup and view all the answers

    What is the main distinction between gradualism and punctuated equilibrium in evolutionary biology?

    <p>Gradualism advocates for slow, continuous change, whereas punctuated equilibrium involves long periods of stability interrupted by brief changes.</p> Signup and view all the answers

    Which type of reproductive barrier occurs before fertilization?

    <p>Gametic isolation</p> Signup and view all the answers

    What is a defining feature of sympatric speciation?

    <p>It is driven by polyploidy in plants.</p> Signup and view all the answers

    What does it mean when evolutionary theory states that evolution is not goal oriented?

    <p>Evolution occurs by chance and environmental pressures without a set direction.</p> Signup and view all the answers

    What role does DNA polymerase play in proofreading DNA mutations?

    <p>It corrects errors during DNA replication.</p> Signup and view all the answers

    What is the primary mechanism by which UV light causes DNA damage?

    <p>It induces the formation of thymine dimers.</p> Signup and view all the answers

    Which of the following accurately describes exon and intron functions in eukaryotic genes?

    <p>Exons code for proteins, while introns are non-coding sequences.</p> Signup and view all the answers

    In the context of the Hardy-Weinberg principle, what does the equation $p + q = 1$ represent?

    <p>The frequencies of alleles in a gene pool.</p> Signup and view all the answers

    What is the significance of the transcription start site (+1) in eukaryotic transcription?

    <p>It is the site where RNA polymerase initiates synthesis.</p> Signup and view all the answers

    What role do nucleases play in nucleotide excision repair?

    <p>They remove damaged DNA segments.</p> Signup and view all the answers

    What is the function of the anticodon on transfer RNA (tRNA)?

    <p>To bind to the complementary codon on mRNA.</p> Signup and view all the answers

    Which form of natural selection favors individuals with extreme phenotypic traits at both ends of the spectrum?

    <p>Disruptive selection</p> Signup and view all the answers

    What is the primary purpose of the polymerase chain reaction (PCR)?

    <p>To amplify specific DNA segments.</p> Signup and view all the answers

    What does heterozygote advantage entail in a population?

    <p>It enhances survival compared to homozygous individuals.</p> Signup and view all the answers

    Study Notes

    Central Dogma (Information Transfer)

    • Information flows from DNA to RNA to protein, a fundamental concept in molecular biology.
    • DNA → RNA → protein

    Friedrich Miescher

    • Discovered "nuclein," a substance later identified as DNA.

    Fred Griffith Experiment (1928)

    • Involving Streptococcus pneumoniae bacteria (rough and smooth strains).
    • Demonstrated a "transforming agent" that caused transformation in bacteria.

    Transforming Agent

    • The material that caused transformation in the Griffith experiment, later discovered to be DNA.

    Virulent

    • In microbiology, this refers to a quality of biological agents that express very potent pathogenicity and can cause severe infections.

    Avery, MacLeod & McCarty Experiment (1944)

    • Confirmed the transforming agent in Griffith's experiment was DNA.

    Hershey & Chase Experiment (1952)

    • Used bacteriophages (T2 phage), crucial evidence supporting DNA as the genetic material.

    Erwin Chargaff

    • Proposed Chargaff's Rules, stating that A = T and G = C in DNA.

    Rosalind Franklin

    • Contributed crucial X-ray diffraction images (Photo 51) of DNA, essential for Watson and Crick's model.
    • Her work at King's College, London.

    Watson & Crick (1953)

    • Proposed the double helix model of DNA structure.
    • Their work was based at Cambridge University.

    DNA Structure

    • DNA is a double helix.
    • Adenine pairs with Thymine, and Guanine pairs with Cytosine.
    • DNA has 5' and 3' ends.

    DNA Replication

    • Occurs during the S phase of the cell cycle.

    Models of DNA Replication

    • Conservative, semi-conservative, and dispersive models were proposed.
    • Meselson-Stahl experiment proved the semi-conservative model.

    Meselson-Stahl Experiment (1958)

    • Used isotopes of nitrogen (light 14N and heavy 15N) to demonstrate semi-conservative DNA replication.

    DNA Replication Process

    • Replication involves origins, replication bubbles, and forks.
    • Synthesis proceeds 5'→3'.
    • Enzymes involved include polymerase, helicase, topoisomerase, ligase, primase, single-strand binding proteins (SSBPs).
    • Deoxyribonucleotide triphosphates (dNTPs) are the building blocks.

    DNA Replication Details

    • DNA polymerase reads the template strand 3'→5', and synthesizes the new strand 5'→3'.
    • DNA polymerase III and I have different roles in replication.
    • Leading and lagging strands are involved in the replication process.

    DNA Damage and Repair

    • DNA polymerase proofreads.
    • Mutagens (e.g., UV light) cause damage.
    • Cells repair damage through various mechanisms (e.g., nucleotide excision repair).
    • E. coli mismatch repair system is an example.

    Gene, Allele, and Traits

    • Genes are units of inheritance.
    • Alleles are different forms of a gene.
    • Dominance and recessiveness describe trait expression.
    • Homozygous (PP, pp) and heterozygous (Pp) relate to gene pairings.

    Transcription

    • Messenger RNA (mRNA) is created from DNA.
    • RNA polymerase reads the DNA template strand 3'→5' and synthesizes the mRNA 5'→3'.
    • Steps include initiation, elongation, and termination.
    • Promoters regulate transcription.
    • Eukaryotic transcription involves introns and exons.

    Genetic Code

    • A set of rules defining how codons translate into amino acids.
    • Codons are three-nucleotide sequences (e.g., AUG is for methionine).

    Translation

    • Ribosomes translate mRNA into proteins.
    • Transfer RNA (tRNA) carries amino acids.
    • tRNA has an anticodon that matches with codons.
    • Ribosomes contain A, P, and E sites.

    Gel Electrophoresis

    • Separates DNA fragments based on size. Agarose and polyacrylamide gels are used.

    Polymerase Chain Reaction (PCR)

    • Amplifies DNA segments exponentially.
    • Uses Taq polymerase, denaturation, annealing, and extension steps.
    • Used in HIV testing and DNA fingerprinting

    DNA Sequencing

    • Determining the order of nucleotides in DNA.
    • Dideoxy sequencing method uses dideoxyribonucleotide triphosphates (ddNTPs).
    • Automated DNA sequencing uses fluorescent labeling.

    Human Genome Project

    • A large-scale effort to map the human genome.

    Genetic Variation in Populations

    • Variation arises from mutations and other sources.
    • Gene pool is the set of alleles in a population.

    Hardy-Weinberg Equilibrium

    • A model for allele and genotype frequencies in a stable population.
    • p + q = 1
    • p² + 2pq + q² = 1

    Evolution

    • Driven by natural selection, genetic drift, and gene flow.
    • Macroevolution refers to large-scale evolutionary change.

    Origin of Species

    • Darwin’s theory of evolution by natural selection.

    Evidence of Evolution

    • Fossils and fossil record
    • Molecular evidence
    • Homologous structures
    • Analogous structures

    Speciation

    • The formation of new species.
    • Mechanisms include allopatric and sympatric speciation.
    • Reproductive isolation prevents interbreeding.

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    Description

    Explore the fundamental concepts of molecular biology, including the central dogma of DNA to protein information flow and key experiments that defined our understanding of genetic material. This quiz covers significant discoveries by scientists like Miescher, Griffith, Avery, and others that shaped the field of genetics.

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