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

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

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

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

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

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

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? http://207.207.4.198/pub/flash/24/menu.swf

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.

DNA replication

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

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

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

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

Translation to Protein