Warm Up Analyze how science can change. Compare and Contrast DNA and RNA.

RNA DNA BOTH ribose (sugar) Deoxyribose (sugar) Nitrogenous base: uracil Deoxyribose (sugar) Nitrogenous base: Thymine Nucleic Acids Made of nucleotides: a five-carbon sugar a phosphate group a nitrogenous base Flexible Nitrogenous bases: Adenine Guanine Cytosine thymine Stable

Analyze DNA and the Chart What do you notice? Base Number A T G C

Chargaff’s Rule C = G T = A

Bases are bonded with Hydrogen bonds. A and T G and C Two hydrogen bonds G and C Three hydrogen bonds

What the Difference? C and T and U A and G Pyrimidine Bases Purine Bases What the Difference?

Drawing Conclusions If A=T and G=C then Purines = Pyrimidines A Purine always bonds with a Pyrimidine

Double Helix DNA is formed by two strands of nucleotides.

How do scientists know?? Wilkins used x-ray diffraction. Watson and Crick used data collected by Wilkins and Chargaff. Built a model.

SO……. Science Changes Scientists use each other research? YES!!!!

Scientists work together to solve problems. Science Changes New knowledge modifications to current knowledge. Individuals and teams have contributed and will continue to contribute to science. Scientists conduct investigations for a many reasons: exploration of new areas discovery of new aspects of the natural world confirmation of prior investigations

DNA Structure DNA often is compared to a twisted ladder. Rails of the ladder are represented by the alternating deoxyribose and phosphate. The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

Orientation Position, direction Parallel Antiparallel

Orientation Of DNA Antiparallel On the top rail, the strand is said to be oriented 5′ to 3′. The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.

Chromosome Structure To fit in a cell DNA coils tightly around histones(proteins) Forms nucleosomes, coil to form chromatin fibers. chromatin fibers supercoil to form chromosomes

Describe the structure of DNA using the following words: Double helix Purine Pyrimidine Phosphate deoxyribose

DNA is a nucleic acid made up of a phosphate, deoxyribose sugar, and nitrogeneous bases. Purine and pyrimididine bases pair up and coil tightly to for a double helix.

Word Wall