What is DNA?
Nov. 5, 2013
Warm up:
1. What is DNA?
2. Why do we
need to learn
about it?
Your answers
should be on the notes page. You
have one minute to finish up!
Yesterday’s Exit Ticket
HOW can scientists study traits? What do
they actually look at?
… Many of you said “GENES”
Can anyone tell me what a “GENE” is?!!!!
Remember Genetic Engineering?
• Genetic engineering is a technique used
by scientists to change the DNA of living
organisms.
Designer Babies?! WHAAAAT?!
The Good=
• Eliminating
Disease
• Helping sick
siblings
Designer Babies?!
The Bad:
• Eventually may reduce variety by selecting “best” traits?
• Playing “God”?
Yesterday’s opinions…
20% said… SURE!
Social status wouldn’t be affected much more than it
already is, it will actually increase equality, it could increase
our nation’s education level, HEALTHY BABIES!
12.5% said… I JUST DON’T KNOW!
AND 67.5% said… NO WAY, JOSE!
Who knows the side effects down the road, technology is
going too far, religious beliefs say you are made they way
you are supposed to be, if you aren’t satisfied with how
your baby may turn out, DON’T HAVE KIDS! (after all, they
are made from YOUR genes, so what is “un-perfect” ?)
So, what is DNA then?
Remember
biomolecules
• DNA is a nucleic acid
• DNA stands for Deoxyribonucleic Acid
• DNA – is the genetic material inside the
nucleus of
eukaryotic cells.
IT ACTUALLY WINDS UP
REALLY TIGHTLY AND FITS
INTO CHROMOSOMES!!!
It is made of
DNA!
Deoxyribonucleic Acid
Segment of DNA
NUCLEUS
CHROMOSOMES
GENES
SEGMENTS
OF DNA
Which cell organelle is DNA
found in (for eukaryotes)?
THE NUCLEUS!
Do prokaryotes even have DNA???
OF COURSE! But, it is
not protected by a
nucleus!
Discovering the Structure of DNA
Structure was discovered in 1953 by James
Watson and Francis Crick
They were only able to
complete the model
after x rays taken of
DNA through a
microscope by a
woman named
Rosalind Franklin
revealed the key to
determining the true
shape….she was
never officially credited
with the discovery 
Watch this!:
DNA ANIMATION!
What is the purpose, or function, of
DNA?
• Stores the genetic information that instructs
the cell on which proteins to make.
• So, DNA makes PROTEINS
(both are biomolecules!)
• Responsible for determining all organism’s
traits such as eye color, body structure, and
enzyme production.
Proteins are
responsible for
most of these
traits!
The Components of DNA
•
DNA is a long molecule made up
of repeating individual units of
monomers called nucleotides.
– Nucleotides are made up of three
parts that are held together by
covalent bonds:
1. Sugar
2. Phosphate Group
3. Nitrogenous Base
Phosphate
Deoxyribose
Sugar
Nitrogenous
Base
In the diagram, what substance
is represented by the letter x?
A. Ribose sugar
B. Deoxyribose sugar
C. Phosphate
D. Adenine
Nitrogenous Bases
•
DNA contains four nitrogenous bases:
1.
2.
3.
4.
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
In DNA, Which Bases Pair?
• Adenine (A) always pairs
with Thymine (T)
• Guanine (G) always pairs
with Cytosine (C)
Watch this!:
COMPOSITION OF DNA
Covalent
bonds
In your notes, write in the base pairs for the following:
These bases are held together by
hydrogen bonds
What are Hydrogen Bonds?
Hydrogen bonds are weak and
they combine the two DNA strands.
It is important
that these
middle bonds
are weak! Why
do you think???
Structure of DNA
• Phosphate Group &
Deoxyribose Sugar
– Form the backbone or
sides of the ladder.
• Nitrogenous Bases
– Form the “steps” of the
ladder or middle of the
molecule.
X makes up the backbone along
with which other molecule?
A. Ribose sugar
B. Deoxyribose sugar
C. Base-pairs
D. Adenine
• DNA is a
DOUBLE
HELIX or a
twisted
ladder.
Pictures Of The Double Helix
THE INSTRUCTIONS
ARE IN THE SEQUENCE
OF NUCLEOTIDES.
The components that make
up the genetic code are
common to all organisms!
A
T
G
C
A
T
C
G
If we all have the
same components
of DNA, why do
we look different
from other people
and from other
organisms like
horses or plants?
DNA of a horse
C
G
A
T
G
C
T
A
DNA of a human
What is the difference?
The difference is in the order of the bases.
The more alike two organisms are, the more alike their order of
bases will be.
Information for everything about an organism is carried in the order
of bases in their DNA, like a language.
DNA base pairs  genes  proteins  traits
This sequence of base pairs
is what determines our traits
BUILDING A DNA MODEL:
• You should have the following materials:
•
•
•
•
•
•
•
1 piece of white copy paper (watch how I fold it!)
8 phosphates
8 sugars
2 adenine bases
2 thymine bases
2 guanine bases
2 cytosine bases
• Use what you learned today to create a DNA
model!
• Before you glue, have me check!
EXIT TICKET QUICK-WRITE:
Using as much of the vocabulary below,
describe the structure and function of DNA.
deoxyribose
double helix
nucleotide
Watson and
Crick
cytosine
covalent
bonds
genetic
information
thymine
base pair
nitrogen base
phosphate
3’ to 5’
5’ to 3’
protein
synthesis
genetic code
adenine
nucleus
hydrogen
bond
guanine
traits
YOU HAVE FIVE MINUTES!