DNA
presented by Mrs. Sanford
7th Grade Life Science
Lost Mountain Middle School
DNA (Deoxyribonucleic Acid)
chemical code
- a master copy of
instructions for cell
structure and
function
- agenda
- blueprints
- owner’s manual
DNA (Deoxyribonucleic Acid)
chemical code
- gives you your
characteristics
- traits like hair color,
eye color, height,
heartbeat, hearing,
personality, talents
DNA (Deoxyribonucleic Acid)
chemical code
- organic compound
- contains carbon
- nucleic acid
DNA (Deoxyribonucleic Acid)
structure (what it looks like) - three dimensional
- double helix
- spiral staircase
- twisted ladder
DNA (Deoxyribonucleic Acid)
structure
- sides or “handrails”
are made of sugars
and phosphates
- ‘ribo’ is for ribose, a
sugar
DNA (Deoxyribonucleic Acid)
structure
- cross pieces, “rungs” or
“steps” are made of
nitrogen base pairs
- same two bases always
pair
- adenine, thymine (A, T)
- cytosine, guanine (C, G)
DNA (Deoxyribonucleic Acid)
discovery/history
1950’s
- x-rayed by Rosalind
Franklin
Rosalind Franklin
DNA X-ray
DNA (Deoxyribonucleic Acid)
discovery/history
1950’s -1960’s
- Maurice Wilkins gives
Franklin’s x-rays to
Watson and Crick
- Francis Crick and
James Watson make
a model of DNA
DNA (Deoxyribonucleic Acid)
discovery/history
1960’s
- Franklin dies of
cancer
- Wilkins, Watson, and
Crick share a Nobel
Prize for the model
DNA (Deoxyribonucleic Acid)
DNA Model
DNA Model
Sketch
Wilkins
Watson
and
Crick
DNA (Deoxyribonucleic Acid)
DNA replication
- copying happens in
interphase
- Watson and Crick also
modeled this
DNA (Deoxyribonucleic Acid)
DNA replication
- enzymes break apart
the bases
- RNA collects extra
bases from the
cytoplasm
DNA (Deoxyribonucleic Acid)
DNA replication
- the extra bases pair
with the broken DNA
strands
- new handrails form
from sugars and
phosphates
DNA (Deoxyribonucleic Acid)
DNA replication
- two new strands
have been created
DNA (Deoxyribonucleic Acid)
Mutation
- damaged chromosomes
(strands of DNA)
- deleted/inserted base pairs
DNA (Deoxyribonucleic Acid)
Mutation
- mistakes in the DNA
- example: albinism
Your Turn
Use the model kit to
make a replica of
DNA
Review kit colors
- Same two bases
always use same two
colors
- adenine and
thymine (A, T)
- cytosine and
guanine (C, G)
- How is your model
like the real DNA?
- How is it different?
- Where is DNA found
in cells?
- What does it look like
when inside the cell’s
nucleus?