1. DNA Structure and Function Notes
Biology - Ms. Spinale

2. Introduction
Genetic information in all living things is stored in DNA, which is present in chromosomes.
Most of your DNA is the same as other humans - a small percent is different, making each of us unique.

3. Double helix = two strands twisted tightly together.
DNA Structure
Double helix = two strands twisted tightly together.
Each strand is made up of a series of smaller molecules joined together called nucleotides.

4. There are three parts to each nucleotide:
Nucleotides
There are three parts to each nucleotide:
1. a nitrogen base.
2. a deoxyribose (sugar)
3. a phosphate group.

5. Deoxyribose and phosphate:
Nucleotides
DNA stores genetic information in the sequence of nitrogen bases along one strand of DNA.
Deoxyribose and phosphate:
same in all nucleotides.
“sides of ladder.”

6. Nucleotides
Nitrogen base:
different - DNA nucleotides may contain only 1 of 4 nitrogen bases.
like letters in a code - order of base along one strand conveys information capable of translating code.

7. DNA has a four letter code.
Nitrogen Base Pairs
DNA has a four letter code.
A = Adenine.
T = Thymine.
C = Cytosine.
G = Guanine.
Bases are paired.

8. A A T G G C A T T A G C C A T G G T T A C C G T A A T C G G T A C C
Nitrogen Base Pairs
A and T always bond together.
C and G always bond together.
A A T G G C A T T A G C C A T G G
T T A C C G T A A T C G G T A C C

9. DNA in each cell contains 3,000,000,000 base pairs.
Nitrogen Base Pairs
DNA in each cell contains 3,000,000,000 base pairs.
These base pairs make up about six feet of coiled DNA, which are organized into 46 chromosomes in each cell nucleus (some DNA in mitochondria and chloroplasts).

10. Each chromosome is one very long piece of DNA.
Nitrogen Base Pairs
Each chromosome is one very long piece of DNA.

11. DNA is the code for making proteins in cells.
The Role of DNA
DNA is the code for making proteins in cells.
Proteins make a phenotype (physical characteristic that can be seen).
DNA has genes, genes code for proteins, proteins make traits.

12. DNA Replication
How can one DNA molecule be replicated to make another identical molecule? Predictable interactions between nitrogen bases.

13. Complementary Base Pairing:
DNA Replication
Complementary Base Pairing:
Pairing is always the same.
A (larger) - T (smaller)
G (larger) - C (smaller)
DNA acts as a template for its own replication.

14. Enzymes are key to replication:
DNA Replication
Enzymes are key to replication:
separate strands.
read nucleotide sequence on one strand.
facilitate synthesis of new strand.
At completion, we have two molecules.
Each molecule contains one old strand and one new complementary strand.

16. Mutations in DNA Replication
Repair enzymes check and fix DNA when mutations are detected.
Passed to offspring when mutation is in gamete.

17. Mutations in DNA Replication
1. Deletion mutation - missing nucleotide, changes the code.
2. Substitution mutation - puts wrong base (same size) in the spot.

18. Ribose instead of deoxyribose.
Structure of RNA
Ribose instead of deoxyribose.
Uracil (U) substitutes for thymine.
Single strand instead of double strand.

19. Types of RNA
Messenger RNA - mRNA - produced using DNA as a pattern so code may be carried out of the nucleus.
Transfer RNA - tRNA - brings amino acids in the order specified by the bases on mRNA.

20. Types of RNA
Ribosomal RNA - rRNA - type of RNA in ribosomes, site of the actual protein production in the cytoplasm.

21. DNA RNA Shape 2 strands Location Cytoplasm Bases Thymine Sugar Ribose
Comparing DNA and RNA
DNA
RNA
Shape
2 strands
Location
Cytoplasm
Bases
Thymine
Sugar
Ribose

22. DNA RNA Shape 2 strands 1 strand Location Nucleus Cytoplasm Bases
Comparing DNA and RNA
DNA
RNA
Shape
2 strands
1 strand
Location
Nucleus
Cytoplasm
Bases
Thymine
Uracil
Sugar
Deoxyribose
Ribose