DNA REVIEW Objective: To review the structure and function of DNA.
Introduction You are made up of billions of cells and each cell has its own unique set of 46 chromosomes. A chromosome is just one big long chain of DNA! DNA (Deoxyribonucleic Acid) contains all the information that determines who you are!
DNA DNA is often called the blueprint of life. DNA contains the instructions for making proteins within the cell.
Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of DNA.
The Shape of the Molecule DNA is a very long polymer. (chain of nucleic acids) Its basic shape is like a twisted ladder or zipper. It is called a double helix.
The Double Helix Molecule The DNA double helix has two strands twisted together.
One Strand of DNA phosphate The backbone of the molecule is alternating phosphates and deoxyribose sugar. Nitrogenous bases are attached to the backbone. deoxyribose nitrogenous bases
Four nitrogenous bases DNA has four different bases: Cytosine C Thymine T Adenine A Guanine G
Thymine and Cytosine are pyrimidines. Thymine and cytosine each have one ring of carbon and nitrogen atoms. C N O cytosine C N O thymine
Adenine and Guanine are purines. Adenine and guanine each have two rings of carbon and nitrogen atoms. C N O Guanine C N Adenine
Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together?
Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. To the right: Cytosine and Guanine hydrogen bonded
Hydrogen Bonds, cont. When making hydrogen bonds: Cytosine always pairs up with Guanine. Adenine always pairs up with Thymine. To the right: Adenine and Thymine hydrogen bonded
Important: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G
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