We will be discussing the structure of DNA in this article. Deoxyribonucleic acid is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses. DNA and ribonucleic acid are nucleic acids.
DNA stands for
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
The phosphate and sugar form the
backbone of the DNA molecule,
whereas the bases form the “rungs”.
There are four types of nitrogenous
Each base will only bond with one
other specific base.
Form a base
Form a base
Adenine <==> Thymine
Guanine <==> Cytosine
The sides of the DNA
ladder are phosphate &
sugar held together by
Because of this complementary base
pairing, the order of the bases in one
strand determines the order of the
bases in the other strand.
Base Pair Rule
One side: A T A T C A T G C G G G
To crack the genetic code found in
DNA we need to look at the sequence
The bases are arranged in triplets
A gene is a section of DNA that codes for
Each unique gene has a unique sequence
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, for 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 form words....
Words form sentences....
Let's Review What We Know
1. DNA stands for: De _____ ribo ______ acid
2. What is the shape of DNA? _______________
3. Adenine always pairs with _______________
4. The sides of the DNA ladder are deoxyribose and _____
5. Guanine always pairs with _____________
6. What is the complimentary sequence: A A T G C A
7. The two sides of DNA are held together by _______
8. DNA is composed of repeating subunits called
9. What are the 4 bases that make up the rungs of the DNA