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Chapter 6. Genes and DNA. Chapter 6.1. What Does DNA Look Like?. DNA Model. Scientists were unsure of what a DNA (Deoxyribonucleic acid) looked like. In the 1950’s 2 scientists discovered the structure. The Pieces of the Puzzle.
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Chapter 6 Genes and DNA
Chapter 6.1 What Does DNA Look Like?
DNA Model • Scientists were unsure of what a DNA (Deoxyribonucleic acid) looked like. • In the 1950’s 2 scientists discovered the structure.
The Pieces of the Puzzle • They knew that the material that made up genes must do 2 things. • It must be able to give instructions to cells • It must be replicated every time the cells divide.
Nucleotides • DNA is made up of nucleotides. • Nucleotides are made up of a sugar, phosphate and base. • There are 4 different bases in DNA • Adenine - A • Thymine - T • Guanine - G • Cytosine - C
Chargaff’s Rules • There is always an equal amount of adenine and thymine. • There is always an equal amount of guanine and cytosine
Rosalind Franklin • Helped discover more about the structure of DNA. She used a process called x-ray diffraction to create images of the DNA.
Watson and Crick Model • After seeing Franklin’s images they concluded that DNA looked like a long twisted ladder.
DNA’s Structure • The twisted ladder shape of DNA is referred to as a double helix. • The 2 sides of the ladder are made of alternating sugar and phosphate parts. • Adenine on one side always pairs with thymine on the other. • Guanine on one side always pairs with cytosine on the other.
Making Copies of DNA • The pairing of A T and G C allows for DNA replication to occur. • Pairs of bases are complementary • CGAC will always pair with GCTG
Replication • Step 1: the DNA is unzipped down the middle where the bases meet. • Step 2: each side is now used as a pattern for the new DNA. • Step 3: complementary bases match up with the original strand. • Step 4: two strands have now been created from the one.