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DNA. The Molecule Of Life. DNA Structure. Nucleotides The Backbone Base Pairing The Double Helix Chromosomes Nucleosomes Genes. Nucleotide: the basic molecule of DNA. 3 parts: Nitrogenous base Sugar Phosphate. 5’. 3’. Nucleotides: 4 bases.

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DNA

The Molecule Of Life


Dna structure
DNA Structure

  • Nucleotides

  • The Backbone

  • Base Pairing

  • The Double Helix

  • Chromosomes

  • Nucleosomes

  • Genes


Nucleotide the basic molecule of dna
Nucleotide: the basic molecule of DNA

3 parts:

  • Nitrogenous base

  • Sugar

  • Phosphate

5’

3’


Nucleotides 4 bases
Nucleotides: 4 bases

The nucleotides in DNA use 4 different bases:

  • Guanine G

  • Cytosine C

  • Adenine A

  • Thymine T

    * Just think G-CAT, you know that rapper


Nucleotide bases 2 classes
Nucleotide Bases: 2 classes

Purine:

  • Adenine

  • Guanine

    Pyrimidine

  • Cytosine

  • Thymine

Purines Pyrimidines


The backbone
The Backbone

  • Nucleotides combine by covalent bond between phosphates and sugars


A single strand of dna

5’

A single strand of DNA

Written as: 5’-ACTGTCAAGGTCGAT-3’

3’

3’


Base pairing
Base Pairing

Hydrogen Bonds for spontaneously between specific nitrogenous bases

Pairing Rule:

  • Cytosine bonds with Guanine C-G

  • Thymine bonds with Adenine T-A



A double strand of dna
A Double Strand of DNA

5’

3’

3’

5’


How a dna strand is written
How a DNA strand is written

5’ - ATAGGGCCTAGAACCTGG - 3’

3’ - TATCCCGGATCTTGGACC - 5’

Strands are anti-parallel


Try writing one yourself
Try writing one yourself

3’ - TTAAGCTATGCT - 5’

What is the complementary DNA strand?


Now draw a double strand including bases and backbones
Now draw a double strand, including bases and backbones

5’ - ATGC - 3’

Does your diagram have sugars, phosphates, and nitrogen bases?

Are the strands anti-parallel?

Where are covalent bonds between nucleotides?

Where are the hydrogen bonds?




Dna within a cell
DNA within a Cell

  • DNA combine with proteins called histones to create structures called chromosomes

  • Each cell contains many chromosomes, each with a specific DNA sequence


A nucleosome
A Nucleosome

  • DNA strands are tightly wrapped around histone proteins to create a complex known as a nucleosome


Genes
Genes

  • A gene is a specific sequence of DNA nucleotides

  • The DNA sequence contains the information necessary to build a protein

  • Each specific gene codes for a specific protein


How much dna is there
How much DNA is there?

The human genome contains 3 billion base pairs of DNA, about the same amount as frogs and sharks. But other genomes are much larger. A newt genome has about 15 billion base pairs of DNA, and a lily genome has almost 100 billion.


Unravel all the dna in your body
Unravel all the DNA in your body…

…and it would stretch to the moon!


Junk dna
Junk DNA

  • Only a very small percentage of your DNA (1.5%) is actually composed of coding genes, most of it is repetitive sequences or other non-coding sequences

  • We still don’t know what the other 98.5% of DNA in our cells are for.

  • We’ve still got a whole lot to learn


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