Intro to DNA

Intro to DNA

By David Fink

​Deoxyribonucleic acid or DNA is the molecule of heredity. It contains the genetic blueprint for life. For organisms to grow and repair damaged cells, each cell must be capable of accurately copying itself. So how does the structure of DNA allow it to copy itself so accurately?

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Refer to the diagram in Model 1.

What are the three parts of a nucleotide?

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Refer to the diagram in Model 1.

What kind of sugar is found in a nucleotide?

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Refer to the diagram in Model 1.

Which nucleotide component contains nitrogen?

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Refer to the diagram in Model 1.

Name the four nitrogen bases shown in Model 1.

Draw

DNA is often drawn in a “ladder model.” Locate this drawing in Model 1.

Circle a single nucleotide on each side of the ladder model of DNA.

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DNA is often drawn in a “ladder model.” Locate this drawing in Model 1.

What part(s) of the nucleotides make up the rungs of the “ladder”?

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DNA is often drawn in a “ladder model.” Locate this drawing in Model 1.

What parts of the nucleotides make up the sides (backbone) of the “ladder”?

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DNA is often drawn in a “ladder model.” Locate this drawing in Model 1.

Look at the bottom and top of the “ladder” in Model 1. Are the rungs parallel (the ends of the strands match) or antiparallel (the ends of the strands are opposites)?

Draw

On the ladder model of DNA label each of the bases with the letter A, T, C or G.

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Refer to Model 1.

When one nucleotide contains adenine, what type of base is the adenine

attached to on the opposite nucleotide strand?

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The two strands of DNA are held together with hydrogen bonds between the nitrogen bases.

These are weak bonds between polar molecules.

How many hydrogen bonds connect adenine to its partner base?

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Refer to Model 1.

When one nucleotide contains cytosine, what type of base is the cytosine attached to on the opposite nucleotide strand?

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How many hydrogen bonds connect cytosine to its partner?

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Use a complete sentence to write a rule for how the bases are arranged in the

ladder model of DNA.

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Write the complementary bases to the strand below according to the base-pair rule.

A T C C A G

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The ladder model of DNA is a simplified representation of the actual structure and shape of a DNA molecule. In reality, the strands of DNA form a double helix. Refer to the double helix diagram in Model 1 and describe its shape using a complete sentence.