DNA Structure

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DNA by the NumbersDNA by the Numbers

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DNADNA• The blueprint for an

organism’s structure and function

• Contains the instructions for making proteins within the cell.

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James Watson & Francis Crick’s Model

Rosalind Franklin

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Why is DNA DNA so important?• Found in all organisms

(connects all living things to one another)

• Medical research – treatments and cures

• Agriculture, GMO

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Chromosomes, Genes, and DNAChromosomes, Genes, and DNA

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The Shape of DNAThe Shape of DNA

A “twisted ladder”•Called the double helix.

Subunits: Nucleotides (made of 3 components)

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nucleotideDeoxyribose sugar

1.base3.

phosphate2.

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One Strand (side) of DNAOne Strand (side) of DNA• The backbone of the

molecule is alternating – deoxyribose sugar– Phosphates

• Bases attached to sugars

phosphate

Deoxyribose sugar

bases

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Four BasesFour Bases

• Adenine A• Thymine T•Cytosine C• Guanine G

DNA has four different bases:

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Base Pairing: Base Pairing: Complimentary StrandsComplimentary Strands• Adenine (A) with Thymine (T)

A T• Cytosine (C) with Guanine (G)

C G

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Two Stranded DNATwo Stranded DNA

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Knowledge CheckKnowledge Check1. What are the 3 components that make up

DNA? (6 points)

2. Make a simple sketch of a DNA molecule. Use different shapes to represent the 3 different components and label one of each on your sketch. (4 points)

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How do you think DNA is replicated?How do you think DNA is replicated?

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Considerations:• Two identical copies of the DNA molecules come

from one original DNA molecule.

• Special enzymes are involved in DNA replication. (An enzyme is a type of protein that can move, break apart, or attach different molecules to one other.)

• The DNA molecule can be broken, torn, or split apart.

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•The DNA molecule unravels from the histone proteins around which it is spooled.

Step 1Step 1

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•A special enzyme called Helicase “unzips” the DNA molecule, breaking it down the middle.

Step 2Step 2

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•Another enzyme called DNA Polymerase attaches new complimentary nucleotides to each strand, completing two new DNA strands.

Step 3Step 3

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