DNA Deoxyribonucleic Acid. What do we remember about Nucleic Acids?

DNA

Deoxyribonucleic Acid

What do we remember about Nucleic Acids?

What is DNA?

or Deoxyribonucleic Acid Is a type of Nucleic Acid

– Used for storing and transmitting genetic info– Is in ALL Living Organisms

Eukaryotes –in nucleus only Prokaryotes- free floating

Who Discovered the structure of DNA ?

James Watson and Francis Crick discovered the shape of DNA

The shape is a Double Helix or a twisted ladder

What is DNA composed of?

DNA is a polymer (a large biomolecule)

– It is made of repeated units of Nucleotides, monomers

– Nucleotides have three parts:

Phosphate group Sugar Nitrogen base

What is the backbone of DNA?

The sides of DNA make up the backbone.

– Composed of the phosphate group and sugar from the Nucleotides

Nitrogen Bases of DNA

The rungs of the ladder or middle of DNA hold the sides together. They are made from four types of Nitrogen bases they are bonded together by hydrogen bones

– Adenine (A)– Thymine (T)– Cytosine (C)– Guanine (G)

Types of Bases and How they pair up

Based on their shape the bases are placed in two groups

– Purines double ring Adenine and Guanine

– Pyrimidines single ring Cytosine and Thymine

What is Chargoff’s rule?

When analyzing the bases of DNA it was always found that the

– # A = #T– #C = # G

Through for it was concluded when the two strands of DNA pair up the bases pair up a certain way.

– Adenine pairs with Thymine– Cytosine pairs with Guanine

Let’s Practice

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

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

Ways we studied DNA and why it is DNA important.

Scientist Wilkins and Franklin studied DNA using X-ray machines

Today we use Gel electrophoresis to compare segments of DNA.

DNA is important because it lets us know who we are related to and if their are any diseases that might be passed on to us from an ancestor.

Every Cell in an Organisms has the same DNA

In each individual organisms, every cell has the exact same DNA .– Ex the DNA in your

hair is the same as the DNA in your toes

DNA Replication

Because every cell needs DNA, DNA replicates as cells divide.

How does DNA Replicate?

Step 1: Un whined and Unzip– Double helix straightens ups and the two DNA strands

break apart at the Hydrogen bonds

Step 2: Add Nucleotides– The two strands serve as a template that determines the

order of Nucleotides along a new strand

Step 3: Zip up– The nucleotides connect to each other to form the sugar

phosphate back bone

Step 4: Back to Double Helix

DNA is Semi conservative

Each molecule of DNA that is made is Semiconservative– One strand is Old and one strand is New

Lets practice

Original DNA Two DNA Molecules

A-T

T-A

C-G

G-C

C-G

A-T