Genetics Overview and History
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Genetics Overview and History

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What is the primary focus of genetic studies?

  • The study of heredity and trait transmission (correct)
  • The study of evolution
  • The analysis of chromosomes only
  • The functionality of proteins

    • According to Mendel's laws, a trait may not show up in an individual but can still be passed on to the next generation.

    True

    What did Griffith hypothesize was transferred to the non-virulent r-strain bacteria?

    Transforming principle

    The _______ strain is virulent and has a smooth polysaccharide capsule.

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

    Match the following scientists to their contributions to genetics:

    <p>Gregor Mendel = Laws of Inheritance Frederick Griffith = Transforming principle Oswald Avery = Isolated DNA as genetic material Alfred Hershey &amp; Martha Chase = Phage experiments identifying DNA</p> Signup and view all the answers

    Which experiment demonstrated that DNA is responsible for genetic transformation?

    <p>Avery's Cell-free Extract Experiment</p> Signup and view all the answers

    The Hershey-Chase experiment used radioactive sulfur to label the DNA of bacteriophages.

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

    In the context of Mendel's experiments, what fraction of pea plants are expected to show purebred dominant traits?

    <p>1 out of 4</p> Signup and view all the answers

    What sugar is found in DNA?

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

    RNA is more stable than DNA.

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

    Which base is found in RNA but not in DNA?

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

    Adenine pairs with ______ in RNA.

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

    Which of these statements about DNA pairing is true?

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

    Match the types of RNA with their functions:

    <p>mRNA = Transports genetic code to ribosomes tRNA = Brings amino acids for protein synthesis</p> Signup and view all the answers

    DNA is found in the nucleus of a cell.

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

    What is the process called by which mRNA copies genetic code?

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

    What does a radioactive Sulphur label in bacteria indicate?

    <p>Proteins carry genetic information</p> Signup and view all the answers

    Rosalind Franklin identified three distinct configurations of DNA based on her x-ray crystallography work.

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

    What are the four types of nitrogenous bases in DNA?

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

    In DNA, adenine pairs with ______.

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

    Which structure was proposed by Watson and Crick?

    <p>Double helix</p> Signup and view all the answers

    Match the following components of a nucleotide with their descriptions:

    <p>Adenine = Purine base Thymine = Pyrimidine base Phosphate group = Links nucleotides Ribose = Sugar in RNA</p> Signup and view all the answers

    In DNA, cytosine forms two hydrogen bonds with guanine.

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

    DNA consists of two ______-phosphate backbones.

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

    What is the role of ribosomal RNA (rRNA) in protein production?

    <p>Component of the ribosome</p> Signup and view all the answers

    Supercoiling of DNA makes it less compact than relaxed DNA.

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

    What are the three steps of DNA replication?

    <p>Initiation, Propagation, Termination</p> Signup and view all the answers

    DNA topoisomerases regulate DNA supercoiling by _____ the winding and unwinding of DNA strands.

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

    Match the following classes of DNA topoisomerases with their functions:

    <p>Class I = Breaks one strand of a DNA helix Class II = Breaks two strands of a DNA helix Topoisomerase I = Does not need ATP Topoisomerase II = Requires ATP hydrolysis for its function</p> Signup and view all the answers

    Which enzyme is responsible for strand separation during DNA replication?

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

    DNA replication is a fully conservative process.

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

    What is the 'origin of replication'?

    <p>The point at which DNA replication begins</p> Signup and view all the answers

    What is the primary function of DNA polymerase III?

    <p>To synthesize the new DNA strand</p> Signup and view all the answers

    DNA replication is a continuous process with no interruptions.

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

    What is the role of ligase during DNA replication?

    <p>To join Okazaki fragments</p> Signup and view all the answers

    The single-stranded DNA binding protein (SSB) prevents the strands from _______.

    <p>binding again</p> Signup and view all the answers

    Match the following components involved in DNA replication with their functions:

    <p>DNA polymerase I = Replaces RNA primers with DNA nucleotides Dna primase = Synthesizes RNA primers SSB protein = Prevents re-annealing of DNA strands Exonuclease activity = Proofreads DNA to increase fidelity</p> Signup and view all the answers

    Which direction does DNA polymerase add nucleotides to the new strand?

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

    The leading strand is synthesized discontinuously.

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

    What is the purpose of the termination site sequence in DNA replication?

    <p>To signal the end of DNA replication</p> Signup and view all the answers

    Study Notes

    Genetics

    • The study of how traits are passed from parents to offspring.
    • Genes are units of information about traits.

    History of Genetics

    • Mendel's Laws of Inheritance:
      • Inheritance of traits is determined by genes passed from parents.
      • Individuals inherit one gene from each parent for each trait.
      • Traits can be hidden but still passed on.
    • Griffith transformation experiment:
      • Virulent (S-strain) bacteria have a smooth capsule, causing infection.
      • Non-virulent (R-strain) lacks the capsule, not causing infection.
      • Heat-killed S-strain mixed with live R-strain resulted in lethal infection.
      • Transformation factor transferred from S-strain enabled R-strain to become virulent.
    • Oswald Avery:
      • Isolated a cell-free extract from S-strain.
      • This extract transformed living R-strain into both S-strain and R-strain cells.
      • Only DNase destroyed the "transforming principle", confirming DNA as the genetic material.
    • Hershey-Chase Experiment:
      • A phage is a virus containing DNA and a protein coat.
      • Phages labeled with radioactive sulfur (protein) or phosphorous (DNA) infected bacteria.
      • Radioactive phosphorous was found in infected bacteria, proving DNA carries genetic information.
    • Rosalind Franklin's X-ray Crystallography:
      • Identified two DNA configurations (a and b forms).
      • Proposed a double-helix structure with precise measurements for diameter, separation, and pitch.
    • James Watson and Francis Crick:
      • DNA is a double-stranded, helical molecule.
      • The sugar-phosphate backbones form the outside of the helix.
      • Nitrogenous bases (A, C, G, T) pair inside, held by hydrogen bonds (A-T, C-G).
      • This structure is called the "genetic code".

    Nucleic Acid Structure

    • A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
      • Purine bases: adenine and guanine
      • Pyrimidine bases: cytosine, thymine, and uracil
    • Double helix structure:
      • Two sugar-phosphate backbones on the outside.
      • Nitrogenous bases paired inside, held by hydrogen bonds.
      • Strands run in opposite directions (antiparallel).
      • This orientation is important for DNA replication and interactions.

    Differences between DNA and RNA

    - **Sugar:** DNA contains deoxyribose; RNA contains ribose.
- **Bases:** DNA has thymine; RNA has uracil.
- **Pairing:** DNA (A-T, C-G); RNA (A-U, C-G).
- **Location:** DNA in the nucleus; RNA forms in the nucleolus and moves to cytoplasm.
- **Reactivity:**  DNA is more stable due to deoxyribose; RNA is reactive.

    Types of RNA

    • Messenger RNA (mRNA): Copies DNA code (transcription) and carries it to ribosomes for protein production.
    • Transfer RNA (tRNA): Brings amino acids to ribosomes for protein synthesis.
    • Ribosomal RNA (rRNA): A structural component of ribosomes.

    DNA Supercoiling

    • DNA folds up on itself to form tertiary structures.
    • Supercoiling allows for compact packaging of circular DNA.
    • Supercoiling changes the shape of DNA, making it more compact.
    • DNA topoisomerases:
      • Regulate DNA supercoiling by winding and unwinding DNA strands.
      • Class I: Break one strand of DNA helix.
      • Class II: Break two strands of DNA helix.

    The Flow of Genetic Information

    • Replication (DNA synthesis): DNA makes a copy of itself.
    • Protein Expression:
      • Transcription (RNA synthesis): DNA code is copied into RNA.
      • Translation (protein synthesis): RNA code is used to create protein.

    DNA Replication

    - **Semi-discontinuous:** Occurs in both directions but at different rates.
- **Semi-conservative:** New DNA contains one original and one newly synthesized strand.
    • Three steps:
      • Initiation: Begins at the origin of replication (oric).
      • Propagation: Elongation of the new strand.
      • Termination: Process ends at a specific termination sequence in the DNA.

    Replication Step 1: Initiation

    • Enzymes:
      • Helicase: Separates DNA strands, forming the replication fork.
      • SSB protein: Binds to single strands to prevent them from rejoining.
      • DNA polymerase III: Synthesizes the new strand, adding complementary nucleotides (5'-3' direction).
      • DNA primase: Synthesizes short RNA primers to initiate DNA replication.
      • Ligase: Joins Okazaki fragments.

    Replication Step 2: Elongation

    • DNA Polymerase III functions:
      • Adds nucleotides in 5'-3' direction.
      • 3'-5' exonuclease activity: Proofreading for accuracy.
      • 5'-3' exonuclease activity: Removes RNA primers or damaged DNA.
    • Semi-discontinuous replication:
      • The leading strand is synthesized continuously in 5'-3' direction.
      • Lagging strand is synthesized discontinuously, forming Okazaki fragments.
      • DNA polymerase I replaces RNA primers, and ligase joins fragments.

    Replication Step 3: Termination

    • Replication is stopped at specific termination sequence in DNA.
    • Termination involves:
      • A termination site sequence.
      • A protein binding to the sequence to stop replication.

    IL 1

    • DNA uses thymine (T) instead of uracil (U) because:
      • Thymine is more stable than uracil, which is important for long-term storage of genetic information in DNA.
      • Uracil is prone to deamination (loss of an amino group), which can lead to mutations if not properly removed.
      • Thymine has a methyl group that helps protect it from deamination, ensuring the integrity of genetic code.

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    Genetics Lecture Notes PDF

    Description

    Explore the fundamental principles of genetics, including the inheritance of traits through Mendel's laws and landmark experiments by Griffith and Avery. Understand how genes function and their role in determining characteristics in organisms. This quiz covers key discoveries that shaped our understanding of genetics.

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