DNA Deoxyribonucleic Acid DNA DNA is often called

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DNA (Deoxyribonucleic Acid)

DNA (Deoxyribonucleic Acid)

DNA • DNA is often called the blueprint of life. • In simple terms,

DNA • DNA is often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell.

Genetic material of cells… • GENES – units of genetic material that CODES FOR

Genetic material of cells… • GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT • Called NUCLEIC ACIDS • DNA is made up of repeating molecules called NUCLEOTIDES

Why do we study DNA? DNA We study DNA for many reasons, e. g.

Why do we study DNA? DNA We study DNA for many reasons, e. g. , • its central importance to all life on Earth, • medical benefits such as cures for diseases, • better food crops.

Chromosomes and DNA • Our genes are on our chromosomes. • Chromosomes are made

Chromosomes and DNA • Our genes are on our chromosomes. • Chromosomes are made up of a chemical called DNA.

The Shape of the Molecule • DNA is a very long polymer. • The

The Shape of the Molecule • DNA is a very long polymer. • The basic shape is like a twisted ladder or zipper. • This is called a double helix.

The Double Helix Molecule • The DNA double helix has two strands twisted together.

The Double Helix Molecule • The DNA double helix has two strands twisted together. • (In the rest of this unit we will look at the structure of one strand. )

Nucleotides One deoxyribose together with its phosphate and base make a nucleotide. O O

Nucleotides One deoxyribose together with its phosphate and base make a nucleotide. O O -P O Nitrogenous base O C C C O Phosphate C C O Deoxyribose

One Strand of DNA • One strand of DNA is a polymer of nucleotides.

One Strand of DNA • One strand of DNA is a polymer of nucleotides. • One strand of DNA has many millions of nucleotides. nucleotide

One Strand of DNA • The backbone of the molecule is alternating phosphate and

One Strand of DNA • The backbone of the molecule is alternating phosphate and deoxyribose. • The teeth are nitrogenous bases. phosphate deoxyribose bases

Nitrogenous Bases • PURINES 1. Adenine (A) 2. Guanine (G) A or G •

Nitrogenous Bases • PURINES 1. Adenine (A) 2. Guanine (G) A or G • PYRIMIDINES 3. Thymine (T) 4. Cytosine (C) T or C

Two Stranded DNA • Remember, DNA has two strands that fit together something like

Two Stranded DNA • Remember, DNA has two strands that fit together something like a zipper. • The teeth are the nitrogenous bases but why do they stick together?

Hydrogen Bonds N C N N C C N C O C N •

Hydrogen Bonds N C N N C C N C O C N • The bases attract each other because of hydrogen bonds. • Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. N C C C N O

Important: • Adenine and Thymine always join together A T • Cytosine and Guanine

Important: • Adenine and Thymine always join together A T • Cytosine and Guanine always join together C G

Watson & Crick proposed… • DNA had specific pairing between the nitrogen bases: ADENINE

Watson & Crick proposed… • DNA had specific pairing between the nitrogen bases: ADENINE – THYMINE CYTOSINE - GUANINE • DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”

DNA Double Helix 5 O 3 3 P 5 O O C G 1

DNA Double Helix 5 O 3 3 P 5 O O C G 1 P 5 3 2 4 4 2 3 P 1 T 5 A P 3 O O P 5 O 3 5 P

DNA by the numbers • Each cell has about 2 m of DNA. •

DNA by the numbers • Each cell has about 2 m of DNA. • The average human has 75 trillion cells. • The average human has enough DNA to go from the earth to the The earth is 150 billion m sun more than 400 or 93 million miles from times. the sun. • DNA has a diameter of only 0. 00002 m.

Genetic Diversity… • Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the

Genetic Diversity… • Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

The Code of Life… • The “code” of the chromosome is the SPECIFIC ORDER

The Code of Life… • The “code” of the chromosome is the SPECIFIC ORDER that bases occur. A T C G T A T G C G G…