Uploaded by Miri Kim

What is DNA

What is DNA?
Ms. Kim
Deoxyribonucleic Acid
• Cells contain information…. But how is this information stored?
The Discovery of the Structure of DNA
What are chromosomes?
• Human karyotype (picture of the chromosomes)
• Long threads of DNA
• Carry genetic information of cell
• Information determines what proteins are made
• Made up of many genes
What are genes?
• Genes are segments of chromosomes that contain the code required
to direct the manufacture of a polypeptide or RNA molecule
• Two complementary strands (double helix)
• Sugar-phosphate backbone
• Made up of four types of nucleotide: A,T,C, and G
• Complementary base-pairing: A-T, C-G
• The genetic information of living things
• Able to self-replicate
DNA Structure
• Double helix: like a
twisted ladder
– Sugar and phosphate form
the “sugar phosphate
– Nitrogen bases bond in
the middle with weak
hydrogen bonds
– All other bonds are strong
covalent bonds
Creating the Helix
• The four nucleotides are either purines, which are double-ringed
structures, or pyrimidines, which are single-ringed structures. These
are referred to as bases.
• The four bases are:
Adenine (A) – a purine
Cytosine (C) - a pyrimidine
Guanine (G) – a purine
Thymine (T) – a pyrimidine
The Characteristics of DNA
• Each of its double strand is a single molecule
• Each strand is a pattern made from four parts called nucleotides
• The two strands are joined together by hydrogen bonds, like rungs of
a ladder
• The two strands wind around each other to create a double helix
The Functions of DNA
• Replication – which means the DNA must be copied every time a cell
• Expression – DNA guides the characteristics that determine all
biological traits of a specific organism. E.g) Red hair, blue eyes in
human, or the various colors of horses.
Complementary nucleotides
• These create base pairs formed by complementary nucleotides
(purine with pyrimidine) connected by hydrogen bonds. Adenine will
only pair with thymine, and cytosine will only pair with guanine. The
hydrogen bonds cause the twisting that is characteristic of a double
Lesson Summary
• DNA stands for deoxyribonucleic acid. It is the master molecule in
every cell, containing genetic information. The main characteristics of
DNA include being a protein, each strand is a single molecule, each
strand is a pattern made of nucleotides, the two strands are joined
together by hydrogen bonds, like rungs on a ladder, and the two
strands wind around each other to create a double helix.
• DNA is composed of base pairs of the nucleotides: adenine with
thymine, and cytosine with guanine.
• The functions of DNA are replication and expression.