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Published byErica Cain Modified over 9 years ago
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Pages: Evolution: The Role of DNA
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Deoxyribonucleic Acid
DNA Deoxyribonucleic Acid
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Vocabulary DNA Nucleotide DNA strand Double helix
Sugar – phosphate backbone Nitrogenous base Complementary Base Pairing A gene A protein
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The Structure of DNA
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DNA – The Molecule of Life
DNA is the genetic blueprint of life
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DNA – The Molecule of Life
DNA is the genetic blueprint of life. In every living cell, chromosomes can be found that contain the DNA and genes that govern the cell.
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Several people were important in discovering DNA and its structure
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Martha Chase and Alfred Hershey
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Demonstrated that DNA and not PROTEINS is the genetic material
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Hershey-Chase Experiments
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Erwin Chargaff Watson and Crick knew:
3. A chemist, Erwin Chargaff, had determined in the late 1940s that the number of purines (ADENINE + GUANINE) in DNA always equals the number of pyrimidines (TYROSINE + CYTOSINE). Further, the amount of ADENINE equals the amount of THYMINE (A = T), and the amount of GUANINE equals the amount of CYTOSINE (G = C)
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Erwin Chargaff 1. ADENINE + GUANINE = THYMINE + CYTOSINE
2. ADENINE = THYMINE GUANINE = CYTOSINE
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It showed that DNA is a double helix.
Rosalind Franklin prepared an X-ray diffraction photograph of DNA It showed that DNA is a double helix.
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James Watson and Francis Crick
DNA Structure and Replication James Watson and Francis Crick
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DNA Structure and Replication
- Watson and Crick built an actual model of DNA out of wire and tin. - This model does indeed allow for differences in DNA structure between species because the base pairs can be in any order. Also, the model suggests that complementary base pairing plays a role in the replication of DNA. “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”
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Overview of DNA James Watson and Francis Crick determined the structure of DNA in 1953 DNA is a long chain of nucleotides The chain is called a DNA strand (How many strands are there?) The two strands form a spiraling ladder, also known as a double helix. Nucleotides bond to each other to hold the strands together
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Long Chain of Nucleotides
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Nucleotide Each nucleotide is a complex of three subunits
Phosphoric acid (phosphate group) A pentose (5 carbon) sugar (deoxyribose) A nitrogen-containing base (nitrogenous base)
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DNA Structure and Replication
Nucleotide DNA Structure and Replication Phosphate group Nitrogenous base Sugar
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2 DNA strands form Double Helix
Phosphate + Sugar = the sides of the ladder = Sugar – Phosphate Backbone Nitrogenous Base = the steps of the ladder
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Nitrogenous Bases Adenine will only pair up with Thymine
There are four types of nitrogenous bases which make up the center rungs of the DNA double helix; Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Adenine will only pair up with Thymine Guanine will only pair up with Cytosine
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COMPLEMENTARY BASE PAIRING
There are four types of nitrogenous bases which make up the center rungs of the DNA double helix; Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Adenine will only pair up with Thymine Guanine will only pair up with Cytosine
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What is a gene and protein?
It is a section or a part of DNA which codes for a particular protein Proteins are chains of amino acids and they perform most of the functions in your body!
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What is a gene and protein?
GENE is a section or a part of DNA which codes for a particular protein Proteins are chains of amino acids and they perform most of the functions in your body!
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What is a gene and protein?
For example: A gene can code (has information) for a protein which gives you different traits (characteristics): an eye color, short fingers, long neck, blond hair…etc
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Genes – DNA - Traits Genes are determined by the DNA molecule, and traits (characteristics) are determined by genes. This means that DNA determines your traits
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Examples of Traits Long Neck
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Examples of Traits Long Neck Blue Eyes
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Examples of Traits Long Neck Blue Eyes Dark Skin
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Examples of Traits Long Neck Blue Eyes Dark Skin Short Tail
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Examples of Traits Long Neck Blue Eyes Dark Skin Short Tail
5 fingers on a hand
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HOMEWORK Molecular Genetics (Section 1) – reading notes Take Home Quiz
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