Basics of DNA

Rosalind Franklin- 1952

●Took the x-ray crystallography
image that lead to the discovery of
DNA’s structure.

Watson and Crick- 1953

●Credited for the discovery of the
structure of DNA

●Used works and ideas of all the
previous scientists to accomplish this

●Won a Nobel Prize for their efforts

Rosalind’s Franklin’s Story- Unsong Hero

James Watson is still alive!!! He is 95 and lives in Chicago!

Think about that… so much of what we know about life was discovered recently
(in terms of a historical timeline… Look at how far we have come in less than a

lifetime!)

●

Where?
○

Located in the nucleus in Eukaryotic cells (every single one…)

●

What?
○

Is classified as a nucleic acid (a type of biomolecule- life’s
chemicals!)

●

Shape?
○

Is a 2 sided molecule

○

The shape is referred to as double helix (twisted ladder)

Multiple Choice

What kind of shape is DNA?

• spherical

• triple helix

• double helix

Multiple Choice

Where is DNA located?

• in the nucleus in Eukaryotic Cell

• in the nucleus in prokaryotic cell

• free floating within a cell

Multiple Choice

What type of biomolecule is DNA?

• lipid

• protein

• nucleic acid

• carbohydrate

1.

Stores genetic information in cells

2.

Copies and passes genetic info on to new cells
a.

(parent 🡪 offspring)

3.

Transmits information
a.

MEANING - provides instructions to cells for making proteins
(blueprint) and carrying out cellular processes

Multiple Choice

What is the function of DNA?

• Stores genetic information in cells

• Producing energy for the cell

• Regulating metabolic processes

● Phosphates and deoxyribose sugars make up

the sides or “backbone” of the structure.

● Nitrogen bases make up the center of the

structure
○Think of them like the rungs of the ladder

● Nitrogen bases are held together in the

center by hydrogen bonds
○Weak , easily broken bonds… just strong enough to
make the two sides stick together.

● There are only four nitrogen bases that exist in DNA
● They can be classified as a purine or a pyrimidine

○

(has to do with their chemical structure/ shape)

Multiple Choice

Which of the following is NOT a component of DNA?

• Adenine

• Ribose

• Cytosine

• Guanine

● Adenine pairs with Thymine (A – T)

○ Think Apples in the Tree

● Cytosine pairs with Guanine (C - G)

○ Think Car in the Garage

● “Chargaff’s rule”

○ Because of how the bases pair up, there will be equal

amounts of the paired bases in a DNA molecule

● The amount of adenine (A) = thymine (T)
● The amount of guanine (G) = cytosine (C)

Multiple Choice

What is Chargaff’s rule?

• There are no pairs on a DNA molecule.

• there will be equal amounts of the paired bases in a DNA molecule

• There will be an unequal amounts of paired bases in DNA molecule

Multiple Choice

Which pairs with Adenine?

• Guanine

• Tryptophan

• Thymine

Multiple Choice

Which pairs with Cytosine?

• Guanine

• Adenine

• Cytosine

Draw

Draw a DNA Molecule:

Multiple Choice

If there are 36 cytosine bases in a segment of DNA, how many guanines would you expect to find?

• 63

• 42

• 36

Open Ended

Write the corresponding bases that pair with the following DNA Strand:

C T A A G C G C T A A T