The Secret Code

Genes Genes, which are sections of DNA, are known to: –Carry information from one generation to the next. –Put that information to work by determining the heritable characteristics of organisms. –Be easily copied, because all of a cell’s genetic information is replicated (copied) every time a cell divides.

How do we know that all of our genetic information comes from DNA? Thanks to many scientists and many experiments over the last ≈ 80 years. Griffith Hershey and Chase Franklin Watson and Crick

DNA Nucleic Acid: Deoxyribonucleic Acid (polymer) Made up of units (monomers) called nucleotides. –Three components: 5-carbon sugar: Deoxyribose A phosphate group A nitrogenous base Nucleotide

DNA Structure Called a double helix –Twisted Ladder –Backbone (sides) : 5-carbon sugar and phosphate groups –Rungs: nitrogenous bases

Nitrogenous bases Our alphabet has 26 letters –Can create many different words  many different sentences  billions of different books of information. DNA’s alphabet has 4 letters –A, T, C, and G –Create 3 letter words  Amino acids  proteins  billions of different organisms

Nitrogenous bases Purines: –Adenine –Guanine Pyrimidines: –Thymine –Cytosine

DNA Replication Replication: The process of making a copy of DNA The “parent” molecule has two complementary strands of DNA. Each is base paired by hydrogen bonding with its specific partner: A with T and G with C A with T and G with C

DNA Unzips The first step in replication is the separation of the two strands. An enzyme called DNA helicase unzips DNA

New nucleotides added Each parental strand now serves as a template that determines the order of the bases along a new complementary strand. an enzyme called DNA polymerase adds the bases

Gaps are closed (zipped closed) The nucleotides are connected to form the sugar- phosphate backbones of the new strands. DNA ligase Each “daughter” DNA molecule consists of one parental strand and one new strand….semi-conservative

Reviewing DNA Replication Replication #2 Replication #3 and more

Here are some interesting Facts! A single strand of DNA (one chromosome) is about 2 inches long when uncoiled. Each human cell contains 46 chromosomes (6 to 9 feet of DNA) Your body contains trillion of cells. All of your DNA (when uncoiled and tied together) could make about 6000 trips from the Earth to the Moon.

A few more cool things about DNA It takes about 8 hours for one of your cells to copy all of its DNA. Our entire DNA sequence is called a Genome…and there is an estimated 3,000,000,000 DNA bases This would take up about 3GB of storage If you could type 60 wpm, 8 hours/day…it would take you 50 years to type this. 99.9% of our DNA is the same…it is the 0.01% that makes you who you are!