Transcript DNA

DNA Structure
 DNA consists of two molecules that are arranged
into a ladder-like structure called a Double
Helix.
 A molecule of DNA is made up of millions of
tiny subunits called Nucleotides.
 Each nucleotide consists of:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base
Cool Facts:
• One chromosome has 50 - 250
 million base pairs.
• DNA is found in the mitochondria.
• mDNA is only found in the egg. Sperm
 has no mitochondria so mDNA is passed
 to offspring from the mother.
• One sequence of DNA is a genome or
 gene.
• Unwind all our DNA, it will stretch from the moon
 and back 6000X.
Nucleotides
Phosphate
Nitrogenous
Base
Pentose
Sugar
Nucleic Acid: CHO, CHO,
CHON, ???
Nucleotides
 The phosphate and sugar form the backbone
of the DNA molecule, whereas the bases form
the “rungs”.
 There are four types of nitrogenous bases.
Nucleotides
A
Adenine
C
Cytosine
T
Thymine
G
Guanine
Nucleotides
 Each base will only bond with one other
specific base.
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
Form a base pair.
Form a base pair.
Chargaff’s Rule
 Adenine must pair with Thymine
 Guanine must pair with Cytosine
 Their amounts in a given DNA molecule will be
about the same.
T
A
G
C
Chargaff’s Rule
 Chargaff discovered that the percentage of A
and T were equal. The same for C and G.
This observation became Chargaff’s rule.
This is always the same no matter what
organisms.
BASE-PAIRINGS
H-bonds
G
2 Bonds
T
C
A
3 bonds
Nitrogenous Bases
 PURINES
1. Adenine (A)
2. Guanine (G)
A or G
 PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
T or C
DNA Structure
 Because of this complementary base pairing,
the order of the bases in one strand
determines the order of the bases in the other
strand.
 “Complementary Rule”
A
T
C
G
T
A
C
G
A
T
G
C
T
A
DNA Structure
 To crack the genetic code found in DNA we
need to look at the sequence of bases.
 The bases are arranged in triplets called
codons.
AGG-CTC-AAG-TCC-TAG
TCC-GAG-TTC-AGG-ATC
DNA Structure
 A gene is a section of DNA that codes for a
protein.
 Each unique gene has a unique sequence of
bases.
 This unique sequence of bases will code for the
production of a unique protein.
 It is these proteins and combination of proteins
that give us a unique phenotype.
Exit Slip
Write the complimentary side of
this strand of DNA on a half sheet of
paper and turn in before you leave:
AGTTCAGT
DNA
Gene
Protein
Trait
Your Task
 Draw a flow chart to
show how to get from:
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