LECTURE                               NUCLEOTIDES: DNA AND RNA

In this lecture you will learn:


DNA (Deoxyribonucleic acid) is made form 3 basic units:
1.  SUGARS
2.  PHOSPHATES
3.  BASES

SUGARS (backbone) note different sugars in DNA and RNA
PHOSPHATES (backbone)
BASES (coding) note 1 different base in RNA than in DNA
When each unit is assembled it is called a NUCLEOTIDE

This one is ATP (adenosine triphosphate)

The sugars and phosphates are in  the backbone which then winds around in a double helix due to the angles of the chemical bonds


 

The bases are attached to the sugars and "stick out" from the backbone to the INSIDE of the double helix

 
The bases hydrogen bond with each other to form "BASE PAIRS".  There are two rules:

1. A single ring only bonds with a double.  This maintains a uniform spacing within the double helix. 
A and G cannot bond
T and C cannot bond

2. A base that needs 3 hydrogen bond can only bond with another base that needs 3 hydrogen bonds, the same is true for those that use 2 hydrogen bonds.

A only bonds with T
C only bonds with G

Hydrogen bonds are weak individually, but strong collectively.  The hydrogen bonds are protective of the DNA bases but the closed DNA can be opened easily by enzymes, like helicase.
 

 


 

NOW GO WATCH THE MOVIE HERE
 

FUNCTION of DNA

DNA is the master copy of all the genes that build and run each cell.  Every cell in the body has its own copy of DNA.  When it is time for a cell to split into daughter cells, a new copy of DNA must first be made and that process of duplicating the DNA is called REPLICATION
 

REVIEW QUESTIONS:
What is the function of DNA?
What are the three components of DNA?
Which components form the backbone of DNA?
Which component forms the rungs of the ladder?
What holds the rungs of the ladder together?
What are the two rules of DNA pairs?
Which of the following bond with each other and why?
A = adenine
C = cytosine
G = guanine
T = thymine

Be sure to know the parts of DNA on sight.