1. Bases on the chromosome
Prokaryotic Chromosome Structure
E. coli bacterium
Bases on the chromosome
DNA of E.Coli contains 4,659,221 base pairs! 1

2. Eukaryotic DNA Structure
Nucleosome
Chromosome
DNA
double
helix
Supercoils
Histones
Nucleus of a human cell: 1m of DNA
Chromatin = DNA wrapped around histones (protein)
DNA + Histone = Nucleosome (Fold DNA into the nucleus) 2

3. Discovering the structure of DNA
DNA = Deoxyribose nucleic acid
Made out of sugars (deoxyribose), phosphates
and nitrogen bases

4. Discovering the structure of DNA
Structure was discovered in 1953 by James
Watson and Francis Crick

5. Discovering the structure of DNA
Rosalind Franklin’s DNA image
“Chargoff’s rule”
A = T & C = G

6. Each new cell needs a copy of the information in order to grow
Why must DNA replicate?
Each new cell needs a copy of the information in order to grow

7. DNA replication
Before DNA strand can be replicated or copied it must be “unzipped”
During the S phase, helicase (enzyme that unzips) starts at many different points. Why?

8. DNA replication DNA is unzipped by helicase.
The enzyme DNA polymerase moves in and fills in the complimentary sequence of nucleotides on each of the parent strands.
The two developing DNA strands separate into two new DNA strands.

9. DNA replication

10. Information, Please
In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out.
1. Why do you think the library holds some books for reference only?
2. If you can’t borrow a book, how can you take home the information in it?
3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell? 10

11. RNA Ribonucleic Acid *single strand *sugar = ribose
*uracil instead of thymine
Three types
Messenger RNA (mRNA)
transfers DNA code to ribosomes
for translation.
Transfer RNA (tRNA) brings
amino acids to ribosomes for
protein synthesis.
Ribosomal RNA (rRNA)
Ribosomes are made of rRNA
and protein. 11

12. Copying part of the DNA into mRNA
Transcription
Copying part of the DNA into mRNA 12

13. Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only) 13

15. Translation to Protein