dna the molecule of life. dna structure nucleotides the backbone base pairing the double helix...
TRANSCRIPT
DNADNA
The Molecule Of Life
DNA StructureDNA 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:1. Nitrogenous
base
2. Sugar
3. Phosphate
5’
3’
Nucleotides: 4 basesNucleotides: 4 bases
The nucleotides in DNA use 4 different bases:
1. Guanine G
2. Cytosine C
3. Adenine A
4. Thymine T
* Just think G-CAT, you know that rapper
Nucleotide Bases: 2 classesNucleotide 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
A single strand of
DNA
Written as: 5’-ACTGTCAAGGTCGAT-3’
5’
3’ 3’
Base PairingBase Pairing
Hydrogen Bonds for spontaneously between specific nitrogenous bases
Pairing Rule:• Cytosine bonds with Guanine C-G• Thymine bonds with Adenine T-A
Base PairingBase Pairing
A Double Strand of DNAA Double Strand of DNA5’
5’3’
3’
How a DNA strand is writtenHow a DNA strand is written
5’ - ATAGGGCCTAGAACCTGG - 3’
3’ - TATCCCGGATCTTGGACC - 5’
Strands are anti-parallel
Try writing one yourselfTry 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’
1. Does your diagram have sugars, phosphates, and nitrogen bases?
2. Are the strands anti-parallel?3. Where are covalent bonds between
nucleotides?4. Where are the hydrogen bonds?
The Double HelixThe Double Helix
High Resolution image of Actual DNA molecule
DNA within a CellDNA 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 NucleosomeA Nucleosome
• DNA strands are tightly wrapped around histone proteins to create a complex known as a nucleosome
GenesGenes
• 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 DNAJunk 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