DNA

“The Molecule of Life”

Do Now

What is DNA? Why is it important? Who helped to discover DNA and it’s

structure? Draw a picture of what you think DNA looks

like.

Objectives

To explain the structure of DNA To identify the different types of bases and

which pair with which. To list the scientists involved in discovering

DNA.

DNA

What do the letters stand for? DEOXYRIBONUCLEIC ACID

Where is it found? In the nucleus (or nuclear region in

prokaryotes)

What is it used for? Blueprints of your genes/traits

What is DNA Made of?

Repeating units of nucleotides

DNA STRUCTURE

Nucleotides: 5 carbon sugar (Deoxyribose) Phosphate Group Nitrogen base

Nitrogenous Bases

Purines Double ring structure *Adenine and Guanine

Pyrimidines Single ring structure * Thymine, Cytosine, Uracil

Nitrogenous Bases

Erwin Chargaff

Chargaff’s rule C= G T = A

Draw in the complimentary sequence

ATGCTAATTCGCATCG

Rosiland Franklin

X-ray Diffraction use of photo 51

X-ray diffraction data helped solve the structure of DNA

Indicated that DNA was a double helix

X-Ray Crystallography

Watson and Crick

Built a model of the double helix that conformed to the others’ research two outside strands consist of alternating

sugar and phosphate molecules cytosine and guanine bases pair to each other

by three hydrogen bonds thymine and adenine bases pair to each

other by two hydrogen bonds

DNA Structure

DNA often is compared to a twisted ladder.

Rails of the ladder are represented by the alternating deoxyribose and phosphate.

The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

Label the parts of the DNA molecule

Structure Worksheet!

Do Now

How does DNA get into EVERY cell of our bodies?

Is it the same in every cell? What is RNA? How is it different from DNA?

Objectives

To understand how DNA is replicated. To compare and contrast DNA vs. RNA.

DNA Replication

Allows cells to get an exact copy of DNA.

Steps to Replication

1- The two DNA strands unwind and separate.

Steps to Replication

2- Nucleotides in the area around the DNA match up base by base with the nucleotides on each TEMPLATE DNA strand. All of the C’s pair with the G’s and all of the

A’s pair with the T’s.

Steps to Replication

3- Each new molecule has one strand of new DNA and one from the original strand.

Replication Animation

http://www.johnkyrk.com/DNAreplication.html

What is DNA responsible for again?

RNA is needed to make proteins!

What is RNA? Ribonucleic Acid

How is it different from DNA? Single Stranded Indefinite shape Uses “uracil” Contains Ribose

Types of RNA

Messenger RNA (mRNA) Located in both the nucleus and the cytoplasm Brings genetic code from DNA to the ribosome

to make protein

Types of RNA

Ribosomal (rRNA) Located within the ribosome Helps make the structure of the ribosome

Types of RNA

Transfer (tRNA) Located in the cytoplasm Brings amino acids to ribosome to build

proteins.

DNARNAProtein

Transcription: Occurs in nucleus Create mRNA from DNA

Translation: Occurs in cytoplasm Takes mRNA and makes proteins with the

help of tRNA.

DNA vs. RNA worksheet!

Do Now

What are the 3 types of RNA? What is the purpose of each of them? What are the names of the two processes

involved in making proteins?

Objectives

To understand how mRNA is made. To determine how proteins are made through

the process of translation.

Transcription

** Only individual genes are transcribed, not a whole DNA molecule.

What is the first step to making a protein?

Transcription

Step 1: DNA molecule unwinds and separates just like in replication.

Transcription

Step 2: RNA nucleotides match up with their complimentary bases on the template strand.

Practice: Write the complimentary mRNA strand from this DNA…

ATCGATGGCAAGCTA

Transcription

Step 3: mRNA detaches once entire gene is done and the DNA recoils.

*Many copies of RNA can be made from the same gene in a short period of time.

Translation

What happens in translation?

Where does this happen?

Translation

Step 1: Translation begins when a ribosome attaches to the beginning end of an mRNA molecule.

*Translation MUST START AT THE LETTERS “AUG”.

* Every 3 letters on the mRNA is called a “Codon” that codes for a specific amino acid.

CODON BINGO!!

Translation

Step 2: A tRNA molecule carrying an amino acid matches up to a complementary codon in the mRNA on the ribosome.

*tRNA molecules contain “Anticodons” which are 3 bases on the tRNA.

Translation

Step 3: The ribosome attaches one amino acid to another as it moves along the mRNA molecule. Amino acids are attached by PEPTIDE

BONDS.

Translation

Step 4: The tRNA molecules are released after the amino acids they carry are attached to the growing chain of amino acids.

Translation

Step 5: The ribosome completes the translation when it reaches a stop codon. The newly made protein molecules in the form of a chain of amino acids, is released.

Practice!

Translate this mRNA sequence. *Remember to start and stop at the right

places!!

TCACTAUGCGGACGGACATTATCG

Translation Practice Worksheet!