Chemical Components of Cells: DNA and Chromosomes
34 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary structural role of histones in chromatin?

  • To degrade DNA during replication
  • To mediate gene expression
  • To provide structure and support to chromatin (correct)
  • To transport nutrients within the nucleus

Which histones are part of the octamer structure within a nucleosome?

  • H2a, H2b, H3, H4 only
  • H1, H3, H4 only
  • H1, H2a, H2b, H3, H4 (correct)
  • H2a, H2b, H4 only

The nucleosome core contains how many nucleotide pairs of DNA?

  • 166 nucleotide pairs
  • 146 nucleotide pairs (correct)
  • 156 nucleotide pairs
  • 136 nucleotide pairs

At neutral pH, nonhistone chromosomal proteins are characterized as?

<p>Largely acidic and negatively charged (B)</p> Signup and view all the answers

How are the five major types of histones present in chromatin in terms of their molar ratios?

<p>1 H1: 2 H2a: 2 H2b: 2 H3: 2 H4 (A)</p> Signup and view all the answers

What role does histone H1 play in the structure of nucleosomes?

<p>It stabilizes the complete nucleosome. (D)</p> Signup and view all the answers

What are 30-nm chromatin fibers primarily composed of?

<p>Nucleosomes connected by linker DNA. (C)</p> Signup and view all the answers

What results after the removal of histones from a metaphase chromosome?

<p>A large halo of unstructured DNA around a protein scaffold. (A)</p> Signup and view all the answers

How is the DNA within a chromosome organized after being condensed to 30-nm fibers?

<p>It is segmented into relaxed loops attached to a protein scaffold. (C)</p> Signup and view all the answers

Which technique is specifically used for the separation of very long DNA strands?

<p>Pulsed-field gel electrophoresis. (B)</p> Signup and view all the answers

What relationship does the total concentration of pyrimidines have with purines?

<p>It is always equal to purines. (D)</p> Signup and view all the answers

What technique did Watson and Crick use to gain information on DNA structure?

<p>X-ray diffraction (D)</p> Signup and view all the answers

What is a significant characteristic of interphase chromosomes?

<p>They are usually not visible with a light microscope. (A)</p> Signup and view all the answers

What type of molecules provide information about the organization of DNA components through their diffraction patterns?

<p>Atoms of the molecules (C)</p> Signup and view all the answers

What is the approximate number of genes found in the smallest known DNA viruses?

<p>9 to 11 genes (B)</p> Signup and view all the answers

Which of the following is primarily found in isolated chromatin?

<p>Proteins (A)</p> Signup and view all the answers

What is the length of the genome of bacteriophage X174?

<p>5386 nucleotides (B)</p> Signup and view all the answers

Which bacterial organism is mentioned to have between 2500 to 3500 genes in its DNA?

<p>E. coli (B)</p> Signup and view all the answers

Who completed experiments that provided preliminary insights into the heredity of traits in organisms?

<p>Gregor Mendel (D)</p> Signup and view all the answers

What year did Gregor Mendel publish his findings on plant hybridization?

<p>1866 (D)</p> Signup and view all the answers

Which substance did Johann Friedrich Miescher isolate that led to the discovery of nucleic acids?

<p>Nuclein (A)</p> Signup and view all the answers

In which decade was the double-helix structure of DNA discovered?

<p>1950s (D)</p> Signup and view all the answers

What was found in the 1940s regarding nucleic acids?

<p>They store and transmit genetic information. (B)</p> Signup and view all the answers

Which statement accurately describes the stability of genetic materials?

<p>DNA is more stable than RNA and proteins. (A)</p> Signup and view all the answers

Where is most of the DNA located within a cell?

<p>In the chromosomes (B)</p> Signup and view all the answers

Which characteristic of DNA distinguishes it from RNA and proteins in terms of molecular composition?

<p>DNA's molecular composition remains consistent within an organism. (C)</p> Signup and view all the answers

What did Avery, MacLeod, and McCarty prove regarding the transforming principle?

<p>The transforming principle is DNA. (A)</p> Signup and view all the answers

What conclusion did Hershey and Chase reach about bacteriophage T2?

<p>Genetic information is located in DNA. (B)</p> Signup and view all the answers

What was discovered about the genetic material of the tobacco mosaic virus?

<p>It consists entirely of RNA. (B)</p> Signup and view all the answers

Which of the following did Watson and Crick use to deduce the double-helix structure of DNA?

<p>Evidences from Chargaff's rule. (D)</p> Signup and view all the answers

What distinct parts do bacteriophage T2 consist of?

<p>50 percent DNA and 50 percent protein. (B)</p> Signup and view all the answers

What key relationship did Chargaff discover about nucleotide concentrations in DNA?

<p>Thymine equal to adenine, cytosine equal to guanine. (D)</p> Signup and view all the answers

Which scientists were involved in the discovery of the double-helix structure of DNA?

<p>Watson, Crick, Wilkins, and Franklin. (B)</p> Signup and view all the answers

In the context of uracil and thymine, which statement is true?

<p>Thymine can form base pairs with adenine. (B)</p> Signup and view all the answers

Flashcards

Nuclein

An acidic substance isolated from pus by Johann Friedrich Miescher in 1868. It was later found to be the key component of nucleic acids, which store and transmit genetic information.

Inheritance

The process by which characteristics of organisms are passed down from one generation to the next.

Gene

The fundamental unit of heredity, responsible for carrying genetic information. Genes are located on chromosomes.

Chromosomes

Structures within the nucleus of a cell that contain DNA and are responsible for carrying genetic information.

Signup and view all the flashcards

Sexual Reproduction

The process of sexual reproduction where chromosomes from the mother and father combine to create a new organism.

Signup and view all the flashcards

Mitosis

The process of cellular division that produces two identical daughter cells from a single parent cell. This is how most cells in the body replicate.

Signup and view all the flashcards

Meiosis

The type of cell division that produces gametes (sperm and egg cells). It results in daughter cells with half the number of chromosomes as the parent cell.

Signup and view all the flashcards

Transcription

The process of transferring genetic information from DNA to RNA.

Signup and view all the flashcards

Chargaff's Rule

The sum of the concentrations of adenine and guanine (purines) always equals the sum of cytosine and thymine (pyrimidines) in DNA. This is due to the base pairing rules where A always pairs with T, and C always pairs with G.

Signup and view all the flashcards

X-ray Diffraction of DNA

X-ray diffraction patterns are produced when X-rays pass through a molecule, allowing scientists to deduce its structure. DNA's characteristic X-ray pattern helped Watson and Crick identify its double helical structure.

Signup and view all the flashcards

DNA structure

DNA is a double-stranded helix with two antiparallel chains of nucleotides bonded together. Each nucleotide is a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine, thymine, guanine, or cytosine.

Signup and view all the flashcards

Supercoiling of DNA

DNA can exist in different states of coiling. Negatively supercoiled DNA is tightly wound, making it more compact and facilitating processes like replication and transcription.

Signup and view all the flashcards

Chromosome Structure in Prokaryotes and Viruses

The organization of DNA within chromosomes differs between prokaryotes and viruses. Prokaryotes generally have a single circular DNA molecule, while viruses have smaller genomes with fewer genes.

Signup and view all the flashcards

E.coli Chromosome Structure

The chromosome of E.coli is a single circular DNA molecule that is compacted and organized within the cell. This structure allows for efficient replication and gene expression.

Signup and view all the flashcards

Chemical Composition of Eukaryotic Chromosomes

Eukaryotic chromosomes are complex structures made of DNA, proteins, and other molecules. Chemical analysis shows that chromatin, the complex of DNA and proteins, is the main component of eukaryotic chromosomes.

Signup and view all the flashcards

Transformation

The process by which genetic information is passed from one organism to another through the uptake of DNA from the environment.

Signup and view all the flashcards

Sia and Dawson's Experiment

In vitro transformation in Streptococcus pneumoniae, where mice were not involved in the process, demonstrating that transformation is a direct DNA transfer event.

Signup and view all the flashcards

Avery, MacLeod, and McCarty's Experiment

The experiment conducted by Avery, MacLeod, and McCarty that definitively proved DNA is the genetic material responsible for transformation. They isolated and purified DNA from heat-killed virulent bacteria and showed that only DNA could transfer the virulent trait to harmless bacteria.

Signup and view all the flashcards

Hershey-Chase Experiment

The Hershey-Chase experiment demonstrating that DNA is the genetic material of bacteriophage T2. They labeled phage DNA with radioactive phosphorus and phage protein with radioactive sulfur, finding that only the labeled DNA entered the bacterial host, showing that DNA carries genetic information.

Signup and view all the flashcards

TMV's Genetic Material is RNA

Viral genetic material, not protein, is composed of RNA. This is different from most organisms whose genetic material is DNA.

Signup and view all the flashcards

DNA Double Helix Structure

The double-helix structure of DNA, discovered by Watson and Crick, consists of two antiparallel strands of nucleotides, held together by hydrogen bonds between complementary base pairs (adenine with thymine, guanine with cytosine).

Signup and view all the flashcards

Deoxyribonucleotides

The chemical units that make up DNA, each containing a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, guanine, thymine, or cytosine).

Signup and view all the flashcards

Polynucleotide Chain

A long chain of linked nucleotides, forming a DNA molecule. Each nucleotide consists of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine, guanine, cytosine, or thymine.

Signup and view all the flashcards

Histones

Proteins that are positively charged at a neutral pH, playing a major structural role in chromatin.

Signup and view all the flashcards

Nonhistone Chromosomal Proteins

A diverse group of proteins that are negatively charged at a neutral pH. Unlike histones, they aren't directly involved in the structural organization of chromatin.

Signup and view all the flashcards

Nucleosome

The basic structural unit of chromatin, consisting of a segment of DNA wrapped around a core of eight histone proteins (two each of H2A, H2B, H3, and H4).

Signup and view all the flashcards

Chromatin

The tightly packed, thread-like structure made up of DNA and histones found in the nucleus of eukaryotic cells.

Signup and view all the flashcards

Nucleosome Core

The region of a nucleosome where the DNA is wrapped around the core of histone proteins. This region typically contains 146 base pairs of DNA.

Signup and view all the flashcards

30-nm chromatin fiber

A more compact form of DNA structure, formed by the coiling of nucleosomes. It plays a crucial role in organizing DNA within the nucleus and regulating gene expression.

Signup and view all the flashcards

Chromosome scaffold

A protein scaffold that helps organize and compact DNA during cell division. It binds to DNA loops and contributes to the characteristic X-shaped appearance of chromosomes.

Signup and view all the flashcards

Gel electrophoresis

A technique used to separate DNA molecules based on their size. It employs an electric field to move DNA through a gel matrix.

Signup and view all the flashcards

Pulsed-field gel electrophoresis

A specialized type of gel electrophoresis used to separate very large DNA molecules. It applies alternating electric fields to separate molecules that are difficult to resolve with standard electrophoresis.

Signup and view all the flashcards

Study Notes

Chemical Components of Cells: DNA and Chromosomes

  • DNA and chromosomes are fundamental components of cells
  • Key publications on this topic include Principles of Genetics (6th ed.) by Snustad & Simmons (2012)
  • Chapter 9 (pp. 192-211) and Chapter 8 (pp. 173-175) are relevant references

Discoveries of Inheritance and Nuclein

  • Gregor Mendel's 1866 "Experiments in Plant Hybridization" explained inherited characteristics
  • Johann Friedrich Miescher (1868) isolated "nuclein" from pus
  • This acidic substance is a precursor of DNA
  • Polynucleotide chains were identified in nuclein in the 1940s
  • DNA's role in storing & transmitting genetic information was established in 1944
  • The double-helix structure of DNA was determined in 1953

Indirect Evidence for DNA as Genetic Material

  • Most cellular DNA resides in chromosomes, correlating with gene transmission during reproduction
  • The DNA composition is uniform across an organism, unlike RNA and protein
  • DNA's stability suggests its role in transmitting information across generations

Griffith's Transformation Experiment (1928)

  • Griffith's experiment showed transformation in Streptococcus pneumoniae
  • The transformation involved non-virulent bacteria becoming virulent due to the reception of DNA-containing 'transforming principle'
  • A depiction (image) of the colony phenotypes exists
  • A summary of Griffith's experimental results showing the transformation process is available
  • He examined different bacteria strains of Streptococcus pneumoniae

Sia and Dawson's Demonstration of Transformation (in vitro)(1928)

  • They confirmed transformation in different bacteria, concluding that mice weren't essential to the transformation process.
  • In vitro experiments showed that the transfer of the transforming principle happened between bacteria.

Avery, MacLeod, and McCarty's Experiment (1944)

  • This experiment demonstrated that DNA is the "transforming principle"
  • They used purified macromolecules, separating the roles of DNA, RNA, and proteins
  • The conclusion was that DNA was central to the transformation process

Hershey and Chase's Experiment (1952)

  • Bacteriophage T2 (virus) experiments on Escherichia coli elucidated that genetic information resides in DNA
  • DNA enters a cell during infection
  • The protein coat of the virus (labelled) is excluded from the bacteria

The Genetic Material of Tobacco Mosaic Virus (TMV)

  • TMV's genetic material is RNA, not protein

Nucleic Acid Structure

  • Nucleotides are the building blocks of nucleic acids
  • Each nucleotide comprises a phosphate group, a sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base (purine or pyrimidine)
  • Different DNA nucleotides (deoxyribonucleotides - dTMP, dCMP, dAMP, dGMP) exist

Structure of a Polynucleotide Chain

  • DNA is a chain of nucleotides linked phosphate-sugar bonds
  • Nucleotides are arranged 5' to 3'

Discoverers of the Double Helix Structure of DNA

  • Watson, Crick, Rosalind Franklin, and Maurice Wilkins

DNA Structure: The Double Helix

  • Erwin Chargaff's research supported the complementary base pairing (A-T, G-C) in DNA
  • X-ray diffraction data provided crucial information on DNA structure
  • A diagram (image) shows the double helix structure, including the antiparallel nature of the strands.

Base Composition of DNA

  • Data provided in a table shows the base composition of DNA for various organisms.

Photograph of the X-ray Diffraction Pattern Obtained with DNA

  • A visual illustration of X-ray diffraction pattern for DNA.

Watson and Crick's Famous Paper on DNA Structure

  • Details about publication specifics and the findings of their discovery

DNA Separation by Gel Electrophoresis

  • Explains the procedure for separating DNA fragments by their size, in order to examine their length

Pulsed-Field Gel Electrophoresis

  • Advanced technique suited for separating very large DNA molecules

Schematic of Electrophoretic Separation of DNA Topoisomers

  • Depicts the differentiation of DNA molecules based on their supercoiling status.

Separation of Relaxed and Supercoiled DNA by Gel Electrophoresis (Image)

  • Demonstrates how relaxed and supercoiled DNA can be differentiated using gel electrophoresis

Intercalation of Ethidium into DNA

  • A depiction showing a molecule intercalating with DNA.

Chromosome Structure in Prokaryotes and Viruses

  • RNA and DNA genome sizes are related to the number of genes coded for.
  • Numbers of genes exist with prokaryotes (bacteria), and different viruses

Diagram of the Structure of the Functional State of the E. coli Chromosome

  • Shows different stages of chromosome condensation within an E. coli bacterium

Chemical Composition of Eukaryotic Chromosomes

  • Eukaryotic chromosomes contain DNA, RNA, and proteins (histones and non-histones)
  • The importance of histones to the structure of chromatin is highlighted
  • The various histone types are identified

The Chemical Composition of Chromatin as a Function of the Total Nuclear Content (Diagram)

  • Illustrates the relative abundance of different components within chromatin

Electron Micrograph and Low-Resolution Diagram of the Beads-on-a-String Nucleosome Substructure

  • Shows the substructure of chromatin, namely the nucleosomes

Diagrams of the Gross Structure of a Nucleosome Core and Nucleosome

  • Diagrammatic visuals of the nucleosome core and the complete nucleosome.

Electron Micrograph and Cryoelectron Micrographs of the 30-nm Chromatin Fibers

  • Images illustrating the existence of 30-nm chromatin fibers and their structure within eukaryotic chromosomes

Electron Micrograph of a Human Metaphase Chromosome

  • Electron micrograph presenting visualization of 30-nm chromatic fibers within a metaphase chromosome.

Electron Micrograph of a Human Metaphase Chromosome from Which the Histones Have Been Removed

  • Visualization of a metaphase chromosome stripped of histones, enabling observation of the scaffold structure.

Diagram Showing the Different Levels of DNA Packaging in Chromosomes

  • Diagrammatic representation of different levels of DNA packaging in chromosomes from a 2-nm DNA molecule to a metaphase chromosome.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

DNA and Molecular Structure of Chromosome PDF

Description

Explore the fundamental components of cells, focusing on DNA and chromosomes. This quiz covers key discoveries in genetics, including Mendel's experiments and the structure of DNA. Review important publications and understand the history of genetic material.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser