Nucleic Acids and Inheritance Quiz
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Questions and Answers

The parental molecule has two complementary strands of ______.

DNA

Nucleotides complementary to the parental strand are connected to form the backbones of the new ______ strands.

daughter

The results supported the semiconservative model of ______ replication.

DNA

In the experiment, bacteria were cultured with a heavy ______.

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

The hybrid molecules produced after the first replication eliminated the ______ model.

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

The second replication produced both light and ______ DNA.

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

DNA replication allows genetic info to be inherited from generation to ______.

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

The parental strands separate and form a replication bubble with two ______.

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

Replication proceeds in both directions until the ______ meet on the other side.

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

Each gene is a unit of hereditary information with a specific DNA ______.

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

Alfred Hershey and Martha Chase found that the phage DNA entered the host cells but phage ______ did not.

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

T2 attaches to the host cell and injects genetic material through the ______ membrane.

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

Unduplicated chromosome → DNA segment from chromosome → ______ begins at multiple origins.

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

Frederick Griffith studied streptococcus pneumoniae to develop a ______.

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

T2 infects E.coli and can turn an E.coli cell into a T2-______ factory.

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

DNA carries the ______ information of the organism.

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

The process by which non-pathogenic bacteria became pathogenic due to external DNA is called ______.

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

Bacteriophages, or phages, are viruses that infect ______.

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

In the experiment, the mixture was ______ to free phage parts.

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

The final step involved ______ the mixture to separate the bacteria from the phage parts.

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

The substance responsible for transformation was determined to be ______.

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

Radioactive labeling showed that while proteins remained outside the cells, ______ was found inside the cells.

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

Erwin Chargaff determined that DNA is a polymer made up of ______.

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

Watson and Crick constructed a model of DNA using knowledge from prior ______.

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

The next RNA primer starts the next ______ fragment, extended by DNA polymerase III.

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

DNA polymerase I replaces RNA primers with ______.

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

DNA ligase joins fragments into a continuous ______.

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

Helicase unwinds the parental DNA double ______.

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

Single-strand binding proteins stabilize the separated ______.

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

The leading strand is synthesized continuously by DNA polymerase in the ______ to 3' direction.

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

Using parental DNA as a template, DNA pol III synthesizes a new DNA strand by adding ______ to an RNA primer.

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

Enzymes detect and repair DNA damage that distorts the ______.

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

A Nuclease is a DNA-cutting ______ that helps in the erosion of genes.

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

The basic unit of DNA packing is called a ______.

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

Euchromatin is characterized as being less compacted and more ______.

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

Each ______ consists of a DNA molecule packed together with proteins.

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

The string between nucleosomes is referred to as ______ DNA.

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

DNA ligase joins Okazaki fragments of the ______ strand.

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

DNA polymerase synthesizes new nucleotides to fill in the missing part, using the ______ strand as a template.

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

Upon finding an incorrectly paired nucleotide, polymerase removes the ______ nucleotide.

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

Most DNA polymerases require a primer and a DNA ______ strand.

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

The rate of elongation is about 500 nucleotides per second in ______.

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

Mismatch repair enzymes remove and replace incorrectly paired ______ that have resulted from replication errors.

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

Telomeres are special nucleotide sequences at the ______ of Eukaryotic chromosomal DNA.

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

Errors may arise after replication, but changes are usually ______.

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

Flashcards

DNA Replication

The process of copying DNA, ensuring genetic information is passed from one generation to the next.

Gene

A unit of hereditary information with a specific DNA sequence.

Hershey-Chase Experiment

Experiment that proved DNA, not protein, is the genetic material of viruses.

T2 Bacteriophage

A virus that infects bacteria, providing evidence for DNA as genetic material.

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Genetic Material of T2

DNA is the genetic material of the T2 bacteriophage, which directs the reproduction of the virus.

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Frederick Griffith

Scientist who worked on bacteria and pneumonia, leading to the discovery of the transformative principle, a crucial step in our understanding of the role of DNA in heredity.

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Replication Bubble

A site where DNA replication begins, allowing DNA to be copied from multiple starting points.

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DNA as genetic material

DNA carries the information needed for an organism or virus to function and reproduce.

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Radioactive labeling experiment

A technique to track the movement of specific molecules (like DNA or protein) by attaching radioactive isotopes to them.

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Transformation

The process by which a nonpathogenic bacteria is changed to pathogenic due to acquiring external DNA

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Phage DNA enters bacterial cell

In experiments, it was observed that phage DNA did enter the bacterial cell, but phage proteins did not.

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Protein is not genetic material

Experiments showed that phage protein did not enter the bacterial cell.

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Erwin Chargaff's contribution

DNA is composed of nucleotides with nitrogenous bases.

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DNA is a polymer

DNA is a long chain-like molecule consisting of repeating units (nucleotides).

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Telomere Shortening & Aging

The gradual shortening of telomeres (protective caps at the ends of chromosomes) is linked to the aging process. Telomeres prevent the erosion of genes, and their shortening is thought to be related to cell aging and senescence.

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Nucleosome

The basic unit of DNA packing in eukaryotic cells. It consists of a segment of DNA wrapped around a core of histone proteins.

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Chromatin

A complex of DNA and protein that makes up eukaryotic chromosomes. During interphase, chromatin exists in a less compact form, allowing access to DNA for replication and gene expression.

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Euchromatin

Less condensed, more dispersed form of chromatin found in the nucleus during interphase, allowing for active gene transcription.

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Heterochromatin

More condensed, denser form of chromatin that is transcriptionally inactive. Found in specific regions of the chromosome, often associated with repetitive sequences.

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Semiconservative Replication

A mode of DNA replication where each new DNA molecule contains one original (parental) strand and one newly synthesized strand.

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Conservative Replication

A replication model where the two original parental strands stay together, forming one daughter DNA molecule, and the newly synthesized strands form another. This model was disproven by the Meselson-Stahl experiment.

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Dispersive Replication

A replication model where parental DNA is fragmented, and the new DNA is a mix of old and new fragments. This model was also disproven by the Meselson-Stahl experiment.

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Replication Fork

A Y-shaped region on DNA where the two parental strands are unwound and separated, allowing new strands to be synthesized.

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Origin of Replication

A specific sequence of nucleotides on a DNA molecule where replication begins.

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How does DNA unwind?

Hydrogen bonds between the nitrogenous bases in the DNA strands are broken, causing the two chains to separate and unwind.

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Template Strand

The original strand of DNA that serves as a model for the synthesis of a new complementary strand.

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DNA ligase

An enzyme that joins Okazaki fragments of the lagging strand during DNA replication. It also connects the 3' end of newly synthesized DNA to the rest of the leading strand.

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DNA polymerase

An enzyme that synthesizes new DNA during replication. It uses an existing DNA strand as a template, adding complementary nucleotides to build a new strand.

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Okazaki fragments

Short DNA sequences that are synthesized on the lagging strand during DNA replication. They are later joined together by DNA ligase.

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Mismatch repair

A process that corrects mismatched nucleotide pairs that may have been accidentally incorporated during DNA replication.

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Mutation

A permanent change in the DNA sequence that can alter the phenotype of an organism. It can be caused by errors during DNA replication.

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Telomeres

Specialized nucleotide sequences found at the ends of eukaryotic chromosomes. They protect the ends of DNA from degradation and prevent the shortening of chromosomal ends during replication.

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Shortening of linear DNA ends

After each round of replication, the lagging strand becomes slightly shorter due to the removal of RNA primer. Telomeres help compensate for this shortening.

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Helicase

An enzyme that unwinds the parental DNA double helix, separating the two strands to allow replication.

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Single-strand binding proteins

Proteins that bind to and stabilize the separated strands of DNA, preventing them from re-pairing until they're used as templates.

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Leading strand

The strand of DNA that is synthesized continuously in the 5' to 3' direction, following the movement of the replication fork.

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Lagging strand

The strand of DNA that is synthesized discontinuously in short fragments called Okazaki fragments, moving in the opposite direction of the replication fork.

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DNA polymerase III

The main enzyme responsible for synthesizing new DNA strands, using the parental DNA as a template and adding nucleotides to a pre-existing DNA strand or an RNA primer.

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RNA primer

A short strand of RNA that acts as a starting point for DNA polymerase to begin synthesizing DNA.

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Study Notes

Nucleic Acids and Inheritance

  • DNA replication allows genetic information to be passed from one generation to the next.
  • Unduplicated chromosome -> DNA segment from chromosome -> Replication begins at multiple origins, forming a replication bubble -> Duplicated and condensed chromosome -> Two DNA molecules.
  • Each gene is a unit of hereditary information with a specific DNA sequence.
  • Initially, proteins were thought to carry genetic information.

Frederick Griffith

  • Studied streptococcus pneumoniae (causes pneumonia) to develop a vaccine.
  • Mixed remains of pathogenic bacteria with non-pathogenic bacteria, resulting in the non-pathogenic bacteria becoming pathogenic.

Transformation

  • Change in genotype and phenotype due to the assimilation of external DNA by a cell.
  • The transforming substance was DNA.

Evidence that DNA Programs Cells

  • Bacteriophages (phages), viruses that infect bacteria, were used as tools by researchers.
  • Viruses are much simpler than cells, consisting mainly of DNA or RNA enclosed by a protein coat.
  • They infect a cell and take over cellular processes.

Alfred Hershey and Martha Chase

  • DNA is the genetic material of the T2 virus.
  • T2 infects E. coli, turning it into a T2-producing factory.
  • T2 reprograms the E. coli cell to produce viruses.
  • The T2 enters E. coli.
  • DNA entered host cells but phage protein did not, demonstrating DNA as the genetic material.
  • DNA carries genetic information during infection.

Experiment in Steps

  • Batch I: Radioactive sulfur for protein.
  • Batch II: Radioactive phosphorus for DNA.
  • Mixed radioactively labeled phages with bacteria and agitated the mixture in a blender to separate phage parts from bacteria.
  • Centrifuged the mixture to separate bacteria (pellet) and phage parts (liquid).
  • Measured radioactivity.

Results & Conclusions

  • Radioactivity from protein remained outside the cells, and radioactivity from DNA was found inside the cells.
  • Phage DNA entered bacterial cells, but phage proteins did not, further supporting that DNA is the genetic material.

Other Notable Experiments: Erwin Chargaff

  • DNA is a polymer of nucleotides.

Structure of DNA

  • Contains a nitrogenous base, deoxyribose sugar, and phosphate group.
  • Adenine, thymine, guanine, and cytosine are the nitrogenous bases.
  • Analyzed the base composition of DNA.
  • DNA base composition varies between species.
  • For each species, A = T and G = C; the amount of adenine equals the amount of thymine, and guanine equals the amount of cytosine.

Watson and Crick

  • Constructed a model of DNA in which the two sugar-phosphate backbones run antiparallel.
  • Created a rope ladder model.

DNA Replication

  • Base pairing rules: A with T and G with C.
  • Two strands are complementary and each stores the information needed to reconstruct the other.

Models of Replication

  • Semiconservative: each of the two daughter molecules will have one old strand and one newly made strand.
  • Conservative: all four DNA strands are present after replication.
  • Dispersive: all four strands have a mixture of old and new DNA

Hershey and Stahl experiment

  • Supported the semiconservative model by showing that DNA replication is semi-conservative.

Replication Process

  • DNA replication begins at origins of replication.

  • Short stretches of DNA sequence initiate the process.

  • Proteins attach to the DNA and separate the two strands (forming a replication bubble), opening up a replication bubble.

  • Replication proceeds in both directions (forming replication forks).

  • Eukaryotic chromosomes may have hundreds or thousands of replication origins.

  • Replication bubbles fuse, speeding up the copying process.

Synthesizing a New DNA Strand

  • DNA polymerases need a primer and start synthesizing from the 3' end of the primer.

Continuous vs Discontinuous Synthesis

  • Leading strand synthesis is continuous
  • Lagging strand synthesis is discontinuous
  • The lagging strand is synthesized as Okazaki fragments
  • Okazaki fragments are then joined by DNA ligase.

DNA Replication Proteins

  • Helicase unwinds parental double helix at replication forks.
  • Single-strand binding proteins stabilize separated strands.
  • Topoisomerase relieves overwinding strain.
  • Primase synthesizes RNA primers at 5' end of leading strand and at 5' of each Okazaki fragment of lagging strand.

Bacterial vs Eukaryotic DNA Replication

  • Prokaryotes have one replication origin, while eukaryotes have multiple.
  • Bacterial replication is significantly faster than eukaryotic.

Errors in Replication

DNA Repair

  • Enzymes detect and repair DNA damage; damaged DNA is cut out and replaced.

Mutation

  • Permanent change in DNA sequence.
  • Changes the phenotype of an organism.

Shortening of Linear DNA Molecules

  • Shortening of linear DNA molecules occurs at the ends of eukaryotic chromosomes.
  • Telomeres are special nucleotide sequences at the ends of chromosomes (prevent erosion of coding DNA).

Chromatin, Nucleosomes, Euchromatin, Heterochromatin

  • DNA is packed into chromosomes using nucleosomes as the basic unit for DNA packing.
  • Euchromatin is less compacted, more dispersed interphase chromatin.
  • Heterochromatin is more compacted, denser.

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Description

Test your understanding of nucleic acids and their role in inheritance. This quiz explores DNA replication, genetic transformation, and the groundbreaking experiments of Frederick Griffith. Challenge yourself with key concepts related to genetics and molecular biology.

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