1. DNA structure

2. DNA Structure H DNA is a polymer of Nucleotides Sugar (5C)
Phosphate Group (C-5)
Nitrogenous Base (C-1)
Phosphate
Pentose
Sugar
Nitrogenous
Base
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Uracil (U)
2 alternatives H
DNA is the hereditary material in humans and almost all other organisms.
DNA consists of two molecules that are arranged into a ladder-like structure called Double Helix.
A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
Each nucleotide consists of a Pentose sugar (called desoxyribose), a Phosphate group and a nitrogen-containing ring structure called a Nitrogenous base
Deoxyribose
(DNA)
Ribose
(RNA)

3. DNA Structure: Nitrogenous Bases
Phosphate
Pentose
Sugar
Nitrogenous
Base
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Uracil (U)
DNA
RNA
DNA is an abbreviation of Deoxyribo Nucleic Acid, a for live very important molecule. A DNA molecule consists of two long strands that twist around each other like a spiral staircase. That is why the molecule is called a double helix. Each strand consists of the backbone of ribose (a sugar) together with phosphate groups and nitrogen bases.
There are 4 different nitrogen bases: Adenine (A), Thymine (T), Cytosine (C) and Guanine (G). These bases are often called after their first letter. The A in a strand can form bonds with the T in the opposite strand and the G can form bonds with the C. They form base pairs. This is why the strands are always each others mirror image, each others complement. They are called complementary strands

4. DNA Structure On each side, nucleotides are joined by covalent bonds.
Sugar and phosphate molecules form the backbone.
rungs
backbone
Two sides bond  the bases form the “rungs”

5. DNA Structure Hydrogen bonds connect the two strands
Each Nitrogenous base has a specific pair
complementary base pairing  the order of the bases in one strand determines the order of the bases in the other strand.

6. DNA Structure Journey into DNA
The order in which the bases are present in the DNA forms a code which determines genetic information. Like notes on a piece of music form a melody, the letters A, C, G and T for the foundation of genetic properties. So despite there are only 4 code letters, the possible lettercombinations of a piece of DNA of just hundred of these basepairs is very large. And when considering the fact that the human DNA consists of 6 million basepairs, DNA is very unique for a person.
Journey into DNA

10. DNA STRUCTURE
DRAW simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses, and bases.

11. Why does cytosine only bond with guanine in DNA?
DNA Replication

12. DNA Replication 5 end Hydrogen bond 3 end 1 nm 3.4 nm 3 end 0.34 nm
Key features of DNA structure
Partial chemical structure
Space-filling model

13. DNA REPLICATION
DNA is replicated during the S (synthesis) stage of the cell cycle.
Each body cell gets a complete set of identical DNA.

14. DNA replication is semiconservative.
Two new molecules of DNA are formed, each with an original strand and a newly formed strand.
DNA replication is semiconservative.
Semiconservative means that each DNA molecule contains one new strand of DNA and one old strand of DNA.
original strand
new strand
Two molecules of DNA

15. The DNA molecule unzips in both directions.
DNA serves as a template.
Enzymes and other proteins do the actual work of replication.
Helicase unzips the double helix.
Helicase does this by breaking the hydrogen bonds in the original DNA strand.
Free-floating nucleotides form new hydrogen bonds with the template strand.
Single strand binding proteins (SSB's) keep strand from joining back together.
nucleotide
The DNA molecule unzips in both directions.

16. DNA polymerase enzymes
bond the nucleotides together to form the double helix.
form covalent bonds between nucleotides in the new strand.
“proofreads” each new DNA strand.
DNA polymerase
new strand
nucleotide

17. Replication Fork location where DNA unwinds New Strand Original strand
Nitrogen Bases
Growth
Growth
Replication Fork
Replication Fork
DNA Polymerase

18. New Strand
Original strand
Nitrogen Bases
Growth
Growth
Replication Fork
Replication Fork
DNA Polymerase

19. Model DNA Replication with K’nex!
Groups of 4
Build the strand on the card in your kit.
Add the complementary base pairs
Show replication fork
Diagram a replication fork!!
Show the enzymes DNA Polymerase & Helicase.