The document provides instructions for students to create a DNA model and complete a worksheet. It begins with an overview of DNA structure, noting DNA is made of nucleotides with four nitrogen bases that pair up in specific ways. It then describes the DNA double helix shape and replication process where the strands separate and each side is copied to form two new double helix molecules. Students are directed to build a DNA model and answer accompanying questions before dismantling it for storage.

1. Turn in midterm
today! HSA # 1
Which of these is a the formula for Photosynthesis?
A. C02 + C6H12O6 H20 + O2
B. C6H12O6 + O2 H20 + C02
C. H20 + C02 C6H12O6 + O2
D. C02 + O2 C6H12O6 + H20

2. Objective
SWBAT create a DNA model in order to
describe the structure and function of DNA
in living organisms.
Topic: DNA Structure and replication
Essential Question: What is DNA made of and
how does it replicate?

3. What is DNA?
The Molecule of Heredity
• DNA makes up your genes. Genes determine
what you look like, also known as your traits.
• Where did you get your genes from?

4. DNA stands for
Deoxyribonucleic acid
The complete instructions for synthesizing all
the proteins for an organism.

5. Heredity
• Think back to the characteristics of life… What
is heredity?
• Chromosomes are the condensed pieces of
DNA.
• DNA/ chromosomes are ALWAYS located in
the nucleus of a cell.

6. DNA: The Structure
The monomer (building block) of DNA molecules
are nucleotides
3 Parts of a nucleotide
Sugar
Phosphate
Nitrogen bases

7. DNA is made up of only FOUR
nitrogen bases…
they are abbreviated with the first letter of their name.
A = Adenine
T = Thymine
G = Guanine
C = Cytosine
A and T always pair together.
G and C always pair together.

8. Genetic Code : the importance of
nucleotide sequences
All organisms have the same
4 bases
The order of the nitrogen
bases causes the
differences between organisms

9. Genetic Differences
No two people look exactly alike… except
identical twins.
Why is that? What makes us all different?
Why do you think identical twins are… well…
identical?

10. DNA: Shape
2 DNA strands twist into a double
helix. Like a twisted ladder.
The sides or “backbone” of the
molecule is made up of sugar and
phosphates.
The “steps” are made of nucleotides.

11. The nucleotides
always pair up
the same way.
A always pairs
with what? T
C always pairs
with what? G

12. DNA to Chromosome

13. Replication of DNA
DNA is replicated before a cell
divides so each new cell gets a
complete set of chromosomes.

14. Replication of DNA
Process in which DNA is copied before cell
division (Mitosis)
Name the phase of the cell cycle responsible for
DNA Replication
Interphase

15. How DNA replicates
1) Enzymes break the hydrogen bond between
nitrogen bases of the 2 DNA strands
2) This causes the 2 DNA strands to unzip
3) Free floating nitrogen bases in the cytoplasm
attach to each side of the DNA strand

16. 4) Another enzyme helps the free floating
nitrogen bases attach to each side of the DNA
strand
5) Continues until the entire DNA molecule is
unzipped and replicated (copied)
6) End up with 2 sides copied and re-twisted

17. Each new double helix has
one old strand and one
new strand

18. Making a DNA model
• You will create a DNA model and complete the
question sheet that goes along with that model.
• When your model is complete ask Ms. Cogswell to
check your work. Then compete the work sheet.
• Take apart your model and place all parts back into
the bag.