1. C-Notes: DNA & RNA General Structures
Stnd: BI.5.a
C-Notes: DNA & RNA General Structures
9/18/13
SWBAT differentiate the difference in structures and function of DNA and
RNA.
Objective:
All life on earth uses a chemical called DNA to carr bby its genetic code or blueprint. In this lesson we be examining the structure of this unique molecule.

2. What is DNA?
Genes (genetic info) are found on Chromosomes that are made up of chemical compound called DNA, or Deoxyribonucleic Acid.
Very long “Large complex polymer” found in the NUCLEUS of all living cells.
Deoxyribonucleic Acid

3. Why is DNA called the “blueprint of life”?
Because DNA contains the instructions for making proteins within the cell.

4. Its central importance to all life of Earth
Why do we study DNA?
Its central importance to all life of Earth
Medical benefits such as cures for diseases
Better Food crops
About better food crops, this area is controversial. There is a Dr. Charles Arntzen who is working on bioengineering foods with vaccines in them. People in poor countries could be immunized against diseases just by eating a banana, for instance.

5. What is the function of RNA?
To carry messages from the DNA (in the nucleus) “blueprints” to the Ribosomes in the cytoplasm of living cells to make Proteins.
**RNA is like a disposable copy of segment of DNA**
**RNA is like a working copy of a single gene**
“Ribonucleic Acid”

6. What are the 3 main difference between DNA and RNA?
RNA is almost exactly like DNA, Except:
Contains the sugar Ribose, instead of dexoxyribose
Single stranded, instead of double-stranded
Contains Uracil instead Thymine.

7. What are the 3 types of RNA? Messenger RNA (mRNA)
Carries a message (genetic code information of DNA ) “blueprint” from the nucleus to the Ribosomes in the cytoplasm.
Ribosomal RNA (rRNA)
Makes up Ribosomes, which makes proteins. (Site of Protein Synthesis)
Transfer RNA (tRNA)
Transport (moves) amino acids to the mRNA to make proteins.

8. What is the general structure of DNA?
In the 1905’s James Watson and Francis Crick, developed the “DOUBLE HELIX” Model of DNA.
According to Watson and Crick, the two strands of DNA molecules that are twisted together are shaped like a “twisted ladder”.

9. Double helix structure of DNA
“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Watson & Crick

10. What is DNA’s arrangement
(structure)?
Double stranded “Double Helix”
The two strands are held together by Hydrogen Bonds
Strands connected at the Rungs
Side of the ladder has alternating sugar and phosphate molecules
Rungs are pairs of Nitrogenous bases.

11. According to Erwin Chargaff:
Why do the 4 Nitrogenous Bases in DNA bond (join) together in a certain order?
According to Erwin Chargaff:
all 4 bases are not in equal quantity. (present in characteristic ratio)
Ex: Humans
Adenine (A)= 30.9%
Thymine (T) = 29.4% (only in DNA)
Uracil (U) = 29.4% (only in RNA)
Guanine (G) = 19.9%
Cytosine (C) = 19.8%
Rules A = T
C = G

12. What are the base pairing of Nitrogenous bases in DNA and RNA?
Two types of Classification Groups
Purine (Double-ring bases)
Adenine (A) and Guanine (G)
Pyrimidine (Single-ring bases)
Thymine (T), Uracil (U) and Cytosine (C)
Chargraff’s RULE!!
Base Pairing Order
A T
2 hydrogen bonds
C G
3 hydrogen bonds
**No other combinations are possible**
Rules A = T
C = G

13. Adenine and Guanine are purines
Double-ring bases C N O
Guanine C N
Adenine

14. Thymine and Cytosine are pyrimidines
Single-ring bases C N O
cytosine C N O
thymine

15. Why do the base pairing of Nitrogenous bases in DNA stick together?
Remember, DNA has two strands that fit together something like a zipper.
The Teeth (nitrogenous bases) attract each other because of hydrogen bonds. C N O
Rules A = T
C = G
When making hydrogen bonds, cytosine always pairs up with guanine
Adenine always pairs up with thymine
Adenine is bonded to thymine here

16. Bonding in DNA 5 3 3 5 hydrogen bonds covalent phosphodiester

17. What is the building blocks of Nucleotides (DNA and RNA)?
Each nucleotide made up of:
A 5-carbon sugar
RNA: ribose sugar
DNA: Deoxyribose sugar
Nitrogenous base
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T) (DNA only)
Uracil (U) (RNA only)
Phosphate group(s)

18. DNA vs. RNA DNA RNA deoxyribose sugar nitrogen bases double stranded
G, C, A, T
T : A
C : G
double stranded
RNA
ribose sugar
nitrogen bases
G, C, A, U
U : A
C : G
single stranded

19. DNA by the Numbers Each cell has about 2 m of DNA.
The average human has 75 trillion cells.
The average human has enough DNA to go from the earth to the sun more than 400 times.
DNA has a diameter of only m.
The earth is 150 billion m
or 93 million miles from
the sun.
If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!