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DNA

The molecule of life, proteins and heredity. DNA. What is DNA?. DNA is a complex macromolecule that contains the genetic information that act as blueprints for making all the components of a cell It contains the complete instructions for making all the proteins for an organism

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DNA

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  1. The molecule of life, proteins and heredity DNA

  2. What is DNA? • DNA is a complex macromolecule that contains the genetic information that act as blueprints for making all the components of a cell • It contains the complete instructions for making all the proteins for an organism • Every part of an organism contains proteins, and their shape and functions determine what an organism looks like, what actions it does, what it can eat, even how it thinks!

  3. DNA • Acts as a long-term storage molecule for information that codes all organisms • DNA is composed of long strings of nucleotides bound together • A Nucleotide has 3 parts • 1. A simple sugar (deoxyribose) • 2. A phosphate group • 3. A nitrogenous base

  4. Nitrogenous bases in DNA • There are 4 different nitrogenous bases that found in DNA: • 1. Adenine (A) • 2. Guanine (G) • 3. Thymine (T) • 4. Cytosine (C) • All the information of DNA is stored in the pattern of these bases in the DNA strand

  5. Base Pairing • DNA bases pair up with each other, this leads to 2 complementing strands • Adenine bonds to Thymine (A-T) • Guanine bonds to Cytosine (G-C)

  6. DNA structure • The long strands of nucleotides pairing with each other lead to a ladder like structure called a double helix • The nitrogen bases form the zipper like middle and the phosphate/sugar group of the nucleotide serve as the backbone

  7. Order matters • If you break down any organism to its DNA they all have the same bases of A, T, G and C. • However the order these bases are arranged in is what separates snails from frogs and from humans etc. • Humans have just over 3 billion base pairs!

  8. Recall… • DNA is replicated during interphase before mitosis and meiosis • Is it important that the DNA that is replicated is identical?

  9. Starts when the 2 strands of DNA separate Each strand serves as a template for incoming bases Since A only pairs with T and G only pairs with C DNA replication

  10. DNA replication • So nucleotide bases will come in and pair with the appropriate counterpart and begin forming 2 strands of identical DNA

  11. There are Many enzymes which allow for DNA replication DNA Polymerase Helicase Primase DNA ligase Enzymes control Replication

  12. DNA Polymerase • This enzyme is what finds and attaches the complementary base to the forming strand of DNA • It can only attach bases in a 5’ to 3’ direction

  13. Leadingvs Lagging strands • Because DNA polymerase can only add bases in a 5’ to 3’ direction it forms both leading and lagging strands • The leading strand can start and continue along as the DNA is unwound • The lagging strand must replicate in chunks, called okazaki fragments, because the DNA polymerase must run in the opposite direction of the unwinding

  14. DNA proofreading • DNA polymerase is extremely accurate, however it does also fix mistakes to increase the fidelity of DNA • This means that DNA replication is extremely accurate!

  15. DNA Helicase • This enzyme is responsible for opening up the strands of DNA to allow replication to begin

  16. Is an enzyme that binds initially to allow DNA polymerase to bind the strand and begin matching base pairs DNA Primase

  17. DNA Ligase • Is an enzyme that comes in and seals the nicks left in the lagging strand

  18. Replication Practice • Complete the complementary strand of DNA if the template strand is ATTCGTTCGTAGC

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