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DNA vs. RNA B-4.1 Compare DNA and RNA in terms of structure, nucleotides and base pairs.
DNA vs. RNA
B-4.1 Compare DNA and RNA in terms of structure,
nucleotides and base pairs.
Key Concepts
l Nucleic Acids: l deoxyribonucleic acid (DNA) l ribonucleic acid (RNA)
l Nucleotides: l nitrogen base, sugar, phosphate group
l Complementary base pairs
What you already know…
Students have no previous knowledge of this concept. It has not been addressed in previous grades.
It is essential for you to know… l Nucleic acids are organic molecules that serve as the
blueprint for proteins and , through the action of proteins, for all cellular activity.
l The two types of nucleic acids: DNA and RNA
l DNA and RNA are both comprised of nucleotides that each have three parts.
l The basic structure of DNA and RNA are different (due to their sugars).
l DNA is double stranded whereas RNA is single stranded.
Objectives Compare DNA and RNA. Recognize the chemical names of the DNA and RNA molecules. Identify the three parts of a nucleotide. Interpret an illustration of a nucleotide. Interpret an illustration of a DNA and a RNA molecule.
Vocabulary Words
1. Bacteriophage 2. Nucleotide 3. Double helix 4. Base pairing rules
History: Griffith & Transformation
l 1928, Frederick Griffith
l Did experiment to find out why some bacteria caused pneumonia.
l Discovered transformation.
A transforming material passed from dead S bacteria to live R bacteria, them deadly.
What exactly was transforming? He didnt quite know.
History: Avery & DNA
l 1944, Oswald Avery
l Repeated Griffith’s work in order to determine which molecule in the bacteria caused it to be transformed.
l Discovered that DNA was the nucleic acid that stored and transmitted genetic material.
History: The Hershey-Chase Experiment
l 1952, Alfred Hershey and Martha Chase
l Studied viruses and discovered bacteriophages.
The Structure of DNA
DNA: Deoxyribonucleic Acid l A long molecule made up of units called
nucleotides. phosphate group
deoxyribose (sugar)
nitrogen-containing base
The Structure of DNA 3 Parts of a Nucleotide
l 5-carbon sugar l deoxyribose
l A phosphate group
l Nitrogenous base l Adenine (purines) l Guanine (purines) l Thymine (pyrimidines) l Cytosine (pyrimidines)
Purine
Pyrimidine
The nitrogen containing bases are the only difference in the four nucleotides. There can be a total of 4 different nucleotides.
The Structure of DNA
Has to be responsible for three things: 1) Genes have to carry info from one generation
to the next. 2) Genes have to put that info to work by
determining heritable traits. 3) Genes have to be easily copied during cell
replication.
The Structure of DNA l The backbone of a
DNA chain is formed by sugars and phosphates
l The nitrogenous bases stick out sideways from the chains like the rungs on a ladder & can be joined together in any way.
l The backbone is connected by covalent bonds.
hydrogen bond covalent bond
l The bases are connected by hydrogen bonds.
Chargaff’s Rules l Erwin Chargaff
l Discovered in any sample of DNA that: l % of guanine and
cytosine are almost equal
l % of adenine and thymine are almost equal
l G=C & A=T l Called base pairing
T A C G
Nucleotides always pair in the same way.
l The base-pairing rules show how nucleotides always pair up in DNA.
l Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.
– A pairs with T – C pairs with G
X-Ray Evidence
l Early 1950s Rosalind Franklin used X-Ray diffraction to get information about the structure of DNA.
l Suggested that DNA is twisted in some type of way.
The Double Helix
l Francis Crick and James Watson built 3-D models of DNA to help understand its structure.
l Discovered that DNA was a double helix.
The Structure of RNA
RNA: Ribonucleic Acid l A long molecule made up of units called
nucleotides. phosphate group
ribose (sugar)
nitrogen-containing base
The Structure of RNA Nucleotides
l 5-carbon sugar l ribose
l A phosphate group
l Nitrogenous base l Adenine (purines) l Guanine (purines) l Uracil (pyrimidines) l Cytosine (pyrimidines)
Purine
Pyrimidine
The Structure of RNA
l RNA: ribonucleic acid
l Sugar is called ribose.
l A disposable copy of DNA.
l Single stranded
l Has uracil instead of thymine like in DNA.
Types of RNA
There are three main types of RNA: 1) Messenger RNA (mRNA)
carries copies of instructions for the assembly of amino acids into proteins from DNA to rest of cell
2) Ribosomal RNA (rRNA)
makes up the major part of ribosomes
3) Transfer RNA (tRNA) transfers amino acids to ribosomes during protein
synthesis
Transcription l Transcription is the
process of copying DNA into RNA. l So that translation can
happen next
l Happens in the nucleus of eukaryotes and the cytoplasm of prokaryotes. l Wherever the DNA is
