Opening Activity DNA is often compared to a ladder or a spiral staircase. Look at the picture above and answer the following questions. 1. How is the structure of DNA similar to that of a ladder or spiral staircase? 2. How is it different from that of a ladder or spiral staircase?
Chapter 13 Section 1: The Structure of DNA Key Vocabulary Terms Adapted from Holt Biology 2008
Genes The instructions for inherited traits. The most basic physical unit of heredity; a segment of nucleic acids that codes for a functional unit of RNA and/or a protein.
DNA Deoxyribonucleic acid - the primary material that contains the information that determines recognizable inherited characteristics in related groups of organisms.
Nucleotide An organic compound that consists of a sugar, a phosphate, and a nitrogenous base; the basic building block of a nucleic-acid chain
Purine A nitrogenous base that has a double-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either adenine or guanine
Pyrimidine A nitrogenous base that has a single-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; thymine, cytosine, or uracil
Transformation A change in genotype that is caused when cells take up foreign genetic material.
Bacteriophages Viruses that infect bacterial cells and cause the cells to produce viruses. Bacteriophages are made up of proteins and DNA
Double Helix A DNA molecule is shaped like a spiral staircase and is composed of two parallel strands of linked subunits.
Deoxyribose The five-carbon sugar in DNA is called deoxyribose it that has one less oxygen atom than ribose.
Nitrogenous Bases In DNA, each nucleotide has the same sugar molecule and phosphate group, but the nucleotide can have one of four nitrogenous bases. The four kinds of bases are adenine (A), guanine (G), thymine (T), and cytosine (C).
Adenine (A) A chemical component of DNA and RNA. The shape of adenine is complementary to either thymine in DNA or uracil in RNA.
Guanine (G) One of the four main nucleobases found in the nucleic acids DNA and RNA. In DNA, guanine is paired with cytosine. Guanine is a derivative of purine.
Thymine (T) One of the four nucleobases in the nucleic acid of DNA. In RNA, thymine is replaced with uracil in most cases. In DNA, thymine(t) binds to adenine (A) via two hydrogen bonds, thus stabilizing the nucleic acid structures.
Cytosine (C) One of the four main bases found in DNA and RNA, it forms three hydrogen bonds with guanine.
Base-Pairing Rules A purine on one strand of a DNA molecule is always paired with a pyrimidine on the other strand. These base-pairing rules are dictated by the chemical structure of the bases.
Paired bases are said to be complementary because they fit together like puzzle pieces. Complementary
Chapter 13 Section 1: The Structure of DNA Notes Adapted from Holt Biology 2008
What is a gene? The most basic physical unit of heredity; a segment of nucleic acids that codes for a functional unit of RNA and/or a protein.
What do the letters D - N - A mean? Deoxyribonucleic acid
What are the subunits (building blocks) of DNA? Nucleotides: The basic building block of a nucleicacid chain
History In the 1800 s, Mendel showed that traits are passed on from parents to offspring through units we now call alleles. (One letter of a genotype.)
History Alleles are a certain form of a gene. The structure of DNA wasn t discovered until the 1950s.
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.
1928 Frederick Griffith studied how two related strains of bacteria cause pneumonia by studying mice. 1. Griffith: Transformation
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
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.
Summary: Of Griffith s Experiments 1.Mice + disease-causing bacteria (S) = death. 2. Mice + harmless bacteria (R) = life. 3. Mice + treated harmless bacteria = death What caused the harmless bacteria to change (transform)?
Griffith concluded that a gene was transferred & changed the harmless bacteria into disease-causing bacteria. He called this process transformation.
2. Oswald Avery 1944 Avery repeated Griffith s experiments and used enzymes that destroyed protein, RNA, and DNA, to determine whether the transforming agent in Griffith s experiments was protein, RNA, or DNA.
The process of transformation DID occur when protein and RNA were destroyed. (mice died) Therefore protein and RNA were NOT transforming the bacteria.
Transformation did NOT occur when DNA was destroyed. (mice lived) This proved DNA was the hereditary material.
3. Hershey-Chase Hershey and Chase studied bacteriophages. Bacteriophages are viruses that infect bacterial cells and cause the cells to produce viruses. By using radioactive isotopes, Hershey and Chase showed that DNA, not protein, is the genetic material in viruses.
Summary Hershey-Chase Experiment: Radioactive markers were used on bacteriophage (viruses). Proteins were labeled with radioactive sulfur. DNA was labeled with radioactive phosphorus.
3. Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:
Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:
Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:
Conclusion: The genetic material of bacteriophage is DNA not protein.
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 DNA, Nucleotide A nucleotide is made up of three parts: a phosphate group, a five-carbon sugar group, and a nitrogencontaining base.
The Shape of DNA, Phosphate Group The phosphate groups and the sugar molecules of nucleotides link together to form a backbone for the DNA strand.
The Shape of DNA, Deoxyribose The five-carbon sugar in DNA is called deoxyribose, from which DNA gets its full name, deoxyribonucleic acid.
The Structure of DNA Three parts of a nucleotide a. Sugar-deoxyribose b. Phosphate c. Nitrogen Base (adenine, guanine, cytosine and thymine)
Your Turn Activity
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.
The Information in DNA 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 nitrogenous (nitrogen) bases: a. adenine Purines double ring structure b. guanine c. cytosine d. thymine Pyrimidines single ring structure
The Information in DNA Bases A and G have a double-ring structure and are classified as purines.
The Information in DNA Bases T and C have a single-ring structure and are classified as pyrimidines.
The Information in DNA A purine on one strand of a DNA molecule is always paired with a pyrimidine on the other strand. Specifically, adenine always pairs with thymine, and guanine always pairs with cytosine.
The Information in DNA, continued Base-pairing rules are dictated by the chemical structure of the bases. The hydrogen bonds between bases keep the two strands of DNA together.
Chargaff s Rule: a. [A]=[T] The amount of adenine equals the amount of thymine. b. [C]=[G] The amount of cytosine equals the amount of guanine. The bases are held together by hydrogen bonds.
The Information in DNA Paired bases are said to be complementary because they fit together like puzzle pieces.
The Information in DNA, continued 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.
Rosalind Franklin X-ray images of DNA showed a helix and two chains of nucleotides
Watson and Crick Used information from Chargaff and Franklin Built models of paper and metal to discover the double helix structure of DNA Awarded the Nobel Prize in 1962.
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.
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.