6A (RS) DNA: Identify components of DNA, and describe
how information for specifying the traits of an organism
is carried in the DNA
What is DNA?
 DNA - deoxyribonucleic acid
 A chemical substance that’s present in the
nucleus of all cells in all living organisms
 controls the production of proteins
 DNA is found in the chromosomes in the nucleus.
 DNA of the chromosomes is the genetic material
that is passed from generation to
generation(Heredity)
 Genetics is the study of heredity
 Genes are sections of DNA.
Eukaryotic Chromosomes
 Contain DNA and proteins called histones
 Tightly packed DNA and proteins form chromatin
 During mitosis, the chromatin condenses to form
tightly packed chromosomes
Nucleic Acids
 Complex molecule that stores and communicates
genetic information
 Two types of Nucleic Acids
 DNA- deoxyribonucleic acid

RNA – ribonucleic acid
DNA Shape
 Double Helix
 The ladder arrangement of DNA is twisted,
producing the characteristic double-helix appearance
DNA Structure
 DNA is made up of nucleotides
Nucleotides Have Three Parts
1.
2.
3.
Phosphate group
Simple Sugar (5-carbon sugar)
Nitrogen Base
Ribose & Deoxyribose
 Ribose is a sugar, like glucose, but with
only five carbon atoms in its molecule
 Deoxyribose is almost the same but lacks
one oxygen atom
 Both molecules may be
represented by the
symbol
The Nitrogen Bases
The most common organic nitrogen bases are:
Adenine
(A)
Thymine
(T)
Cytosine
(C)
Guanine
(G)
Pairing Nitrogen Bases
 Adenine forms a bond
with Thymine (A-T)
Adenine
Thymine
 Cytosine bonds with
Guanine (C-G)
Cytosine
Bases are held together by a hydrogen bond
Guanine
Nucleotides
 Phosphate Group + Deoxyribose+ one base=
(or Ribose)
PO4
Nucleotide
adenine
deoxyribose
Joined nucleotides
PO4
PO4
 A molecule of DNA is
formed by millions of
nucleotides joined
together in a long chain
PO4
PO4
sugar-phosphate + bases
backbone
Do you remember what
kind of chemical reaction
joins monomers together
by removing water?
PO4
PO4
adenine
thymine
PO4
PO4
cytosine
guanine
PO4
PO4
PO4
PO4
Label the Parts