Download Essential Question

Essential Question
What is DNA made of and how
does it code for a genetic trait?
DNA stands for...
Deoxyribonucleic Acid
DNA FACTS
• established by
James Watson
and Francis
Crick
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.
What is a nucleotide?
 Each nucleotide consists of:
1. Phosphate group
2. Pentose Sugar (Deoxyribose)
3. Nitrogenous base (A,T,G,C)
Nucleotides
 The phosphate and sugar form the
backbone of the DNA molecule, whereas
the bases form the “rungs”.
Nitrogenous Bases
A
Adenine
C
Cytosine
T
Thymine
G
Guanine
Key
Phosphate
Deoxyribose (sugar)
Base-Pair Rule
Adenine <==> Thymine
Guanine <==> Cytosine
The sides of the
DNA ladder are
phosphate & sugar
held together
by hydrogen bonds
 Because of this complementary base
pairing, the order of the bases in one
strand determines the order of the
bases in the other strand.
A
T
C
G
T
A
C
A
G
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
Base Pair Rule
One side:
A T A
T C A
T G C
G G G
Other side: T A T
A G T
A C G
C C C
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.
How the Code Works
The combination of A,T,G,C determines what
traits you might have.
Ex:
C A T C A T = purple hair
T A C T A C = yellow hair
• Think of the bases of DNA like
letters.
Letters form words....
Words form sentences....
*endless
combinations
DNA
Gene
Protein
Trait
Let's Review What We Know About DNA
Copy the missing parts of the questions.
1. DNA stands for: _________________________
2. What is the shape of DNA? _______________
3. Who established the structure of DNA? ____________
4. Adenine always pairs with _______________
5. The sides of the DNA ladder are deoxyribose and
_____
6. Guanine always pairs with _____________
7. What is the complimentary sequence: A A T G C A
8. The two sides of DNA are held together by _______
bonds.
9. DNA is composed of repeating subunits called
______________________
10. What are the 4 bases that make up the rungs of the
DNA ladder?
_______________________________________
Let's Review What We Know About DNA
1.
2.
3.
4.
5.
6.
7.
DNA stands for: Deoxyribonucleic acid
What is the shape of DNA? _______________
Double helix
Who established the structure of DNA? ____________
Watson & Crick
Adenine always pairs with _______
Thymine
The sides of the DNA ladder are deoxyribose & phosphate
_____
Guanine always pairs with ____________
Cytosine
What is the complimentary sequence: A A T G C A
TTA CGT
8. The two sides of DNA are held together by Hydrogen
_______
bonds.
9. DNA is composed of repeating subunits called
nucleotides
______________________
10. What are the 4 bases that make up the rungs of the DNA
Adenine Thymine Guanine Cytosine
ladder? _______________________________________
chromosomes
DNA
cell
gene
 Use the image to
complete the following:
 Circle a nucleotide and
label it.
 Label the sugar and
phosphate.
 Label the bases that are
not already labeled.
Phosphate
Deoxyribose (sugar)
T
A
C
G
A
T
C
G
Summary
Write 2 questions that start with
a “Why” on each page of notes.
Write a 3 sentence summary that
answers the essential question.