The Secret Code Genes Genes which are sections

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

• Nucleic Acid: Deoxyribonucleic Acid (polymer) • Made up of units (monomers) called nucleotides. – Three components: • 5 -carbon sugar: Deoxyribose • A phosphate group • A nitrogenous DNA 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: • Pyrimidines: – Adenine – Thymine – Guanine – Cytosine

DNA 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

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 sugarphosphate backbones of the new strands. DNA ligase Each “daughter” DNA molecule consists of one parental strand one new strand…. semi-conservative

• Reviewing DNA Replication • Replication #2 • Replication #3 and more