DNA
The molecule of heredity.
• The molecules of DNA is the
information for life (determine an
organism’s traits)
• DNA achieves its control by
determining the structure of
proteins.
DNA
• Deoxyribonucleic Acid
• nucleotides are the building
blocks of nucleic acid
The Structure of Nucleotide
• DNA is made of repeating
subunits called nucleotides.
.
Phosphate
group
Nitrogenous
base
• Nucleotide –
– Simple sugar
– Phosphate group
– Nitrogenous base
Sugar
• The simple sugar in DNA is called
deoxyribose which gives DNA its name
• In DNA, there are four
possible nitrogenous bases:
– adenine (A)
– guanine (G)
– cytosine (C)
– thymine (T).
• Nucleotides join together to form
long chains
–the phosphate group of one
nucleotide bonds to the sugar of
an adjacent nucleotide(they
form the backbone of the chain)
• the nitrogenous bases stick out
like the teeth of a zipper.
• The DNA molecule is a double helix. It
contains two strands of nucleotides, in
a spiral shape
– Sugar- phosphate chains on the
outside with the nucleotides in the
inside.
– The nucleotides held together by H
bonds between A and T, and also
between G and C. (Base Pairs)
• The sequence of
nucleotides on one strand
is matched perfectly to a
complementary sequence
on the other strand.
• In DNA, the amount of A
= amount of T, and the
amount of G = amount of
C.
The importance of nucleotide
sequences
• The sequence of nucleotides forms the
unique genetic information of an organism.
• The closer the relationship is between
organisms, the more similar their DNA
nucleotide sequences will be.
DNA Replication
Process where DNA copies itself
• Separation of strands
– bonds are broken
between
complementary base
pairs
• base pairing
– The bases of free
nucleotides pair with the
bases of the original DNA
strands
– Each strand builds a
complementary strand
• Results of DNA replication
– 2 DNA molecules
– Each consists of an original strand of
nucleotides and a new strand
• Errors sometime do occur
• The wrong nucleotide is added to the new
strand
• A protein (enzyme) that proofreads the new
DNA strand and corrects the mistake
•
http://www.lewport.wnyric.org/JWANAMAKER/animations/DNA%20Replication%20%20long%20.html
•
http://science.nhmccd.edu/biol/bio1int.htm