13 1 the structure of dna l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 21

13.1: The Structure of DNA PowerPoint PPT Presentation


  • 148 Views
  • Uploaded on
  • Presentation posted in: General

13.1: The Structure of DNA. Objectives. What is genetic material composed of? What experiments helped identify the role of DNA? What is the shape of a DNA molecule? How is information organized in a DNA molecule? What scientific investigation led to the discovery of DNA’s structure?.

Download Presentation

13.1: The Structure of DNA

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


13 1 the structure of dna l.jpg

13.1: The Structure of DNA


Objectives l.jpg

Objectives

  • What is genetic material composed of?

  • What experiments helped identify the role of DNA?

  • What is the shape of a DNA molecule?

  • How is information organized in a DNA molecule?

  • What scientific investigation led to the discovery of DNA’s structure?


Dna the genetic material l.jpg

DNA: The Genetic Material

  • The instructions for inherited traits are called genes. A gene is a small segment of deoxyribonucleic acid, or DNA, that is located in a chromosome.

  • DNA is the primary material that causes inheritable characteristics in related groups of organisms.

  • DNA is a simple molecule, composed of only four different subunits.


Searching for the genetic material l.jpg

Searching for the Genetic Material

  • Three major experiments led to the conclusion that DNA is the genetic material in cells. These experiments were performed by Griffith, Avery, and Hershey and Chase.

    Griffith

  • worked with two related strains of

    bacteria which cause pneumonia

    in mice.

    • Smooth bacteria caused pneumonia

    • Rough bacteria did not cause pneumonia

  • Griffith discovered that when harmless live bacteria were mixed with heat-killed disease-causing bacteria and then injected into mice, the mice died.


Griffith s discovery of transformation l.jpg

Griffith’s Discovery of Transformation


Searching for the genetic material6 l.jpg

Searching for the Genetic Material

  • These results led Griffith to discover transformation.

    • Transformation is a change in genotype that is caused when cells take up foreign genetic material.

  • Griffith’s experiments led to the conclusion that genetic material could be transferred between cells.


Searching for the genetic material7 l.jpg

Searching for the Genetic Material

Avery

  • He wanted to determine whether the transforming agent in Griffith’s experiments was protein, RNA, or DNA.

  • Avery used enzymes to destroy each of these molecules in heat-killed bacteria.

  • Avery’s experiments led to the conclusion that DNA is responsible for transformation in bacteria.


Searching for the genetic material8 l.jpg

Searching for the Genetic Material

  • Hershey and Chase studied bacteriophages.

    • viruses that infect bacterial cells and cause the cells to produce viruses.

  • By using radioactive isotopes,

    • phosphorus-32

      • labeled the DNA because it contains phosphorous and proteins don’t

    • sulfur-35

      • labeled the proteins because DNA doesn’t contain sulfur

  • Hershey and Chase showed that DNA, not protein, is the genetic material in viruses.


Checkpoint l.jpg

Checkpoint

  • What did Griffith study in his experiment?

    • Which strain caused the disease?

    • Which strain was harmless?

    • What was the conclusion of his experiments?

  • Summarize what Avery did in his experiment?

    • What was his conclusion?

  • What 2 things did Hershey and Chase use in their experiment?

    • What was their conclusion?


The shape of dna l.jpg

The Shape of DNA

  • A DNA molecule is shaped like a spiral staircase and is composed of two parallel strands of linked subunits.

  • The spiral shape of DNA is known as a double helix.

  • Each strand of DNA is made up of linked subunits called nucleotides.


The shape of dna12 l.jpg

The Shape of DNA

  • A nucleotide is made up of three parts:

    • a phosphate group

    • a five-carbon sugar group

    • a nitrogen-containing base

  • The phosphate groups and the sugar molecules of nucleotides link together to form a “backbone” for the DNA strand.

  • The five-carbon sugar in DNA is called deoxyribose, from which DNA gets its full name, deoxyribonucleic acid.


The shape of dna13 l.jpg

The Shape of DNA


The information in dna l.jpg

The Information in DNA

  • The information in DNA is contained in the order of the bases, while the base-pairing structure allows the information to be copied.

  • In DNA, each nucleotide has the same sugar group and phosphate group, but each nucleotide can have one of four nitrogenous bases.

  • The four kinds of bases are adenine (A), guanine (G), thymine (T), and cytosine (C).

  • Bases A and G have a double-ring structure and are classified as purines.


The information in dna15 l.jpg

The Information in DNA

  • Bases T and C have a single-ring structure and are classified as pyrimidines.

  • A purine on one strand of a DNA molecule is always paired with a pyrimidine on the other strand.

    • adenine always pairs with thymine

    • guanine always pairs with cytosine.

  • Base-pairing rules are dictated by the chemical structure of the bases.

  • The hydrogen bonds between bases keep the two strands of DNA together.


The information in dna16 l.jpg

The Information in DNA

  • Paired bases are said to be complementary because they fit together like puzzle pieces.

  • Because of base-pairing rules, if the sequence of bases is known for one strand of DNA, then the sequence of bases for the complementary strand can be quickly identified.


Discovering dna s structure l.jpg

Discovering DNA’s Structure

  • Watson and Crick used information from experiments by Chargaff, Wilkins, and Franklin to determine the three-dimensional structure of DNA.

    Chargaff

  • showed that the amount of adenine always equaled the amount of thymine, and the amount of guanine always equaled the amount of cytosine.

    Franklin and Wilkins

  • developed X-ray diffraction images

    of strands of DNA suggested the

    DNA molecule resembled a tightly

    coiled helix.


Discovering dna s structure18 l.jpg

Discovering DNA’s Structure

Watson and Crick

  • used both Chargaff’s data and the X-ray diffraction studies to create a complete three-dimensional model of DNA.

  • Their model showed a “spiral staircase” in which two strands of nucleotides twisted around a central axis.


Checkpoint19 l.jpg

Checkpoint

  • What is the name given to the shape of DNA?

  • What are the 3 parts that make up a nucleotide?

  • What makes up the backbone of DNA?

  • What is the name of the sugar in DNA?

  • What determines the information coded on the DNA?

    • How many different types are there and what are their names?

  • What is the difference between purines and pyrimidines?

  • What are the base pairing rules?

  • What holds to the two strands of DNA together?

  • Name the 3 scientists that played a role in the discover of the structure of DNA and their contribution.


Summary l.jpg

Summary

  • DNA is the primary material that causes inheritable characteristics in related groups of organisms.

  • Three major experiments led to the conclusion that DNA is the genetic material in cells. These experiments were performed by Griffith, Avery, and Hershey and Chase.

  • A DNA molecule is shaped like a spiral staircase and is composed of two parallel strands of linked subunits.


Summary21 l.jpg

Summary

  • The information in DNA is contained in the order of the bases, while the base-pairing structure allows the information to be copied.

  • Watson and Crick used information from experiments by Chargaff, Wilkins, and Franklin to determine the three-dimensional structure of DNA.


  • Login