DNA
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DNA. Deoxyribonucleic acid A polymer Monomers are nucleotides. Nucleotides. Building blocks of DNA 4 types Each type has three parts Ring shaped sugar called deoxyribose Phosphate group Nitrogenous base Single or double ring of carbon and nitrogen atoms with functional groups.

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DNA

  • Deoxyribonucleic acid

  • A polymer

  • Monomers are nucleotides


Nucleotides
Nucleotides

  • Building blocks of DNA

  • 4 types

  • Each type has three parts

    • Ring shaped sugar called deoxyribose

    • Phosphate group

    • Nitrogenous base

      • Single or double ring of carbon and nitrogen atoms with functional groups


Nitrogenous bases
Nitrogenous bases

  • The four nucleotides found in DNA differ only in their bases.

    • Thymine (T)

    • Cytosine (C)

      • These are single ring structures called pyrimidines

-Adenine (A)

-Guaninie (G)

- are larger, double ring structures called purines


Dna strands
DNA Strands

  • Nucleotides are joined to one another by covalent bonds that connect the sugar of one nucleotide to the phosphate group of the next.


This repeating pattern of sugar-phosphate-sugar-phosphate is called the “BACKBONE”

The nitrogenous bases are lined up along this backbone.


Dna structure
DNA Structure called the “BACKBONE”

Double Helix:

Watson and Crick model DNA this way

They created a new model in which two strands of nucleotides wound about each other.

Forming a twisting shape called the DOUBLE HELIX



Complementary base pairs
Complementary Base Pairs outside of the double helix and the nitrogenous bases on the inside.

  • Individual structures of the nitrogenous bases determine very specific pairing between the nucleotides of the two strands of the double helix.

  • These pairing are due to the sizes of the bases and their abilities to form hydrogen bonds with each other


Adenine pairs with Thymine outside of the double helix and the nitrogenous bases on the inside.

Cytosine pairs with Guanine

While the sequence of nucleotides along the length of one of the two DNA strands can vary in a number of ways, the bases on the second strand of the double helix are determined by the sequence of the bases on the first strand.


Each base must pair up with its complementary base. outside of the double helix and the nitrogenous bases on the inside.


Dna replication
DNA replication outside of the double helix and the nitrogenous bases on the inside.

  • is the process of copying a double-stranded deoxyribonucleic acid (DNA) molecule,

  • a process essential in all known life forms.

  • The general mechanisms of DNA replication are different in prokaryotic and eukaryotic organisms.


Dna replication1
DNA replication outside of the double helix and the nitrogenous bases on the inside.

  • In a cell, DNA replication must happen before cell division.

  • Prokaryotes replicate their DNA throughout the interval between cell divisions.

  • Eukaryotes, timings are highly regulated and this occurs during the S phase of the cell cycle, preceding mitosis or meiosis I.


Dna replication2
DNA replication outside of the double helix and the nitrogenous bases on the inside.

  • Each DNA strand holds the same genetic information.

  • Both strands can serve as templates for the reproduction of the opposite strand.

  • The template strand is preserved in its entirety and the new strand is assembled from nucleotides


Enzymes link the nucleotides together and form the two new DNA strands, called daughter strands.

This process of copying the DNA molecule is called

DNA replication


Replication of the double helix
Replication of the Double Helix DNA strands, called daughter strands.

  • More than a dozen enzymes are involved in DNA replication.

  • Each "incoming" nucleotide pairs with its complementary nucleotide on the parent strand.


  • Enzymes called DNA strands, called daughter strands. DNA polymerases (PAHL ih mur ayz ez) make the covalent bonds between the nucleotides of the new DNA strand.

  • The process is fast and accurate

  • an error occurs in only about one of a billion nucleotides.


DNA replication begins at specific sites called origins of replication.

The copying proceeds outward in both directions, creating replication "bubbles".

The parent DNA strands open up as daughter strands grow on both sides of each bubble.



DNA replication occurs before a cell divides, ensuring that the cells in a multicellular organism all carry the same genetic information.

It is also the mechanism for producing the DNA copies that offspring inherit from parents during reproduction.


Dna replication3
DNA replication the cells in a multicellular organism all carry the same genetic information.

  • The resulting double-stranded DNA molecules are identical; proofreading and error-checking mechanisms exist


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