Chapter 12 DNA Structure And Replication

Bell WorkWhat are the four macromolecules that compose

all life?

BellworkIf your DNA is 23.5 % adenine. How much

Guanine is there?

Chapter 12- DNA Structure and Replication
The Recipe Book

Nucleic Acids- Function
Nucleic acids function is storing, copying, and

transmitting instructions for making proteins.
DNA and RNA are nucleic acids!!!
Monomer of Nucleic Acids- Nucleotides
Think of DNA as a recipe book
What is DNA and how does it work?

DNA Storage
DNA stores instructions for making

proteins
The total human genome contains 3 billion

base pairs, enough to fill 1,700 books!
The human genome contains about 25,000-

30,000 separate genes
One single gram of DNA can store 700TB of

data , which is 734003200 MB or over 70 million Taylor Swift songs
Genetic Sequencing Site -

https://www.23andme.com/

Nucleotide- 3 parts

DNA- Nucleotide Structure
 5-carbon Sugar- D stands for deoxyribose.

This connects to other nucleotides’ phosphate groups.
Phosphate Group- used to form phosphate

backbone of a nucleic acid.
Nitrogen Base- functional part of DNA.

Makes up the “coded” message

Four Nucleotides- A,T,G,C
Purines

Pairs
With

Pairs
With

Pyramidines

Nitrogen Base Pairing Rules
Adenine pairs with Thymine ( 2 hydrogen bonds )
A-T
Guanine pairs with Cytosine (3 hydrogen bonds )
G-C
Connected by hydrogen bonding between bases
Allows unzipping and rezipping of DNA
There is a 5th Base, Uracil,- FOUND ONLY IN RNA

DNA Structure

Nitrogen
Base

3’ to 5’

3’ to 5’

Covale nt Bonds

DNA Structure
Complementary bases pairing keeps DNA

information conserved, reduces mutation
Hydrogen bonds hold strands together and

allow DNA to be unzipped and rezipped
Nucleotides are connected by covalent

bonds between sugars and phosphate to create sugar phospate backbone

DNA-Twisted Ladder Structure

DNA- Anti-Parallel Strands
P
o i n t e d d o w n Notice how the strands are running in opposite

directions! (Sugars are upside-down on the