DNA: Intro and History

DNA
History, Structure, Genetics

Learning Target

By the end of this lesson you should understand what DNA is, its structure, and the key scientists involved in its discovery. Today we will learn the history of DNA's discovery and how it revolutionized biology and genetics.

I Can

• Use models to investigate the structure of DNA.

• Describe the structure and function of DNA.

• Discuss how the discovery of DNA, genes, chromosomes, and traits illustrate the nature of science.

Key Vocabulary

• Gene: A section of DNA that codes for a specific trait or characteristic.

• Chromosome: A long thread-like structure made of DNA and proteins that carries genes.

• Double Helix: The twisted ladder structure of DNA, made of two strands.

Multiple Choice

What does DNA stand for?

• Deoxyribonucleic acid
• Denitrogenous acid
• Deribonucleic acid
• Diribonucleic acid

DNA stands for...

DeoxyriboNucleic Acid

• Deoxyribonucleic Acid

• Made of:

  • Phosphate groups

  • Deoxyribose sugars

  • Nitrogenous Bases

• Series of nucleotides creating a long stranded molecule

• Code for ALL life; from us to the bacteria that make us sick!

• ​Molecule resides in the nucleus of eukaryotic cells and freely floats in prokaryotic cells

​

What is DNA?

Multiple Choice

What type of organic molecule is DNA?

• lipid

• protein

• carbohydrate

• nucleic acid

DNA is found in all cells

• DNA is packed tightly within the chromosomes within the nucleus

• Genes are a segment of DNA code for traits

Multiple Choice

Where in the cell is DNA found?

• cytoplasm

• ribosome

• vacuole

• nucleus

• ​DNA = chemical instructions for making proteins

  • Proteins determine your traits!​

​​DNA Function

​

Structure of DNA

• Spiral shaped - Double Helix

• made of repeating subunits called nucleotides

• a nucleotide- composed of a phosphate group, deoxyribose sugar, a nitrogenous base

These alternate to form the ladder-like backbone of DNA​

What do the sugar and phosphate group do?

Nitrogenous bases are the "code" part of DNA and/or RNA. Their order is what tells the cell what to make and how to do it.

4 bases found in DNA; in RNA U replaces T.

BASES include:

Adenine - Thymine (DNA ONLY!)
Cytosine - Guanine

​ (Uracil takes the place of Thymine in RNA ONLY!!) -

​What is a nitrogenous base?

What is the difference between a Purine and a pyrimidine? Purines have a double-ring structure and consist of adenine and guanine, while pyrimidines have a single-ring structure and consist of cytosine, thymine, and uracil.

Multiple Select

A single nucleotide is made of 3 components. Which of the following are components of a single nucleotide?

• sugar

• amino acid

• a nitrogen base

• phosphate group

​Some text here about the topic of discussion.

​Nucleotides

​

• Base pairs = 2 nucleotide​s

  • ​Adenine (A) can only pair with Thymine (T)

  • Guanine (G) can only pair with Cytosine (C)

Multiple Choice

A, G, T, and C are all ______________.

• Organelles

• Nucleotides

Match

Match the following base pairs.

• A

• G

• T

• U

• C

T

C

A

A

G

• T

• C

• A

• A

• G

• ​specific base pairs in a specific order

• code that tells proteins what traits to give you

​Genes

​

= Height Gene

​

​Example

​

ATCG/TAGC = Tall

Multiple Choice

Each section of DNA that codes for a specific trait is called a _______.

• gene

• DNA

• base pair

Discovery of DNA & its Structure

• In 1953, two scientists named Watson and Crick discovered that DNA is made of two chains of nucleotides that are joined together at the nitrogen bases by hydrogen bonds.

• By using special X-ray techniques, another scientist named Rosalind Franklin discovered that DNA is made of two strands and that the sugar & phosphate molecules make up its backbone.

• Watson & Crick put this information together with what they knew and they discovered that DNA is twisted into a shape called a double helix.

• The complementary nitrogen bases make up the “rungs” (steps) of the double helix “ladder” structure

Who Discovered DNA?

• Watson and Crick's discovery

• the two-strand DNA, double helix

• DNA-the molecule containing human genes was discovered in 1953

Let's Draw and label the Structure of the DNA Double Helix

• 8. Hydrogen bonds

• 9. Nucleotide

• 10. Nitrogen base

• 11. Sugar

• 12. Phosphate

• 13. Base pair

• A - Adenine

• T -Thymine

• C - Cytosine

• G - Guanine

  Remember: These 4 bases form complimentary pairs: 

  A pairs with T, C pairs with G.

Poll

How are you feeling about understanding the structure of DNA?

• Really good. It makes sense.

• Okay. I know I will get better.

• Meh. Some of it is still confusing.

• Terrible. None of this makes sense.