1. Unit: Molecular Genetics

2. The traits that you have are mainly due to the genes that you have inherited from your parents. DNA (deoxyribonucleic acid) - nucleic acid found in all cells that controls cellular activity DNA is organized into genes. Humans have about 30,000 genes (made of DNA)! Gene - a sequence of DNA that codes for a protein and thus determines a trait.

4. At specific times during the life of an individual, cells and organisms use the information that is stored in our DNA. (in other words, the gene is expressed resulting in the production of a protein) Genes provide a set of instructions, or a genetic program for an individual’s development.

5. Griffith and Avery (1928, 1944 ) Their work yielded results that suggested that the nucleic acid DNA stores and transmits genetic information from one generation to the next. Hershey and Chase (1952) Their work showed that viral genes are made of DNA, not protein.

6. Erwin Chargaff was a biochemist working at Columbia University in New York. In 1949, he made the observation that the amount of adenine (A) was always equal to the amount of thymine (T) for each organism that he studied. The amount of Guanine (G)was also always equal to the amount of Cytosine (C).

7. 1950’s: X-Ray diffraction was used to study the structures of molecules. How it works: X rays bounce off of the object and are scattered in a pattern onto a piece of film. Scientists then shine a light on the object and study its shadow. Rosalind Franklin and Maurice Wilkins used this technique the winter of 1952 and looked at diffraction photos of fibers of DNA.

8. The X pattern observed is characteristic of a helix shape.

9. Used the data collected by Franklin, Wilkins, Chargaff and others to propose the 3D double helix structure for DNA Their proposal was such an outstanding contribution to science that they received a Nobel Prize in 1962

10. Take 2 minutes to summarize what you have Learned by answering the following question: How was the function and structure of DNA determined?

11.  DNA molecule is a long, twisted, double-stranded structure ( like a spiral staircase)  Each strand consists of a chain of smaller units, called nucleotides

12. 1. A five carbon sugar known as deoxyribose 2. A phosphate group 3. A nitrogen base: This is the part of DNA that can have alternate forms. There are 4 different nitrogen bases A: Adenine T: Thymine C: Cytosine G: Guanine

13. Nucleotides are connected to other nucleotides via covalent bonds, which connect the sugar from one nucleotide to the phosphate group of another. They can be connected in any order.

14. Adenine (A) & Guanine (G) are classified as Purines. Purines are larger molecules. They are made of two rings of carbon and nitrogen atoms.

15. Cytosine (C) & Thymine (T) are classified as Pyrimidines Pyrimidines are made of a single ring of carbon And nitrogen atoms.

16. 5-Carbon Sugar and Phosphate group  The sugars/ phosphate form the backbone of each strand  They are like the side rails of a ladder

17.  This is what connects the two strands, like the rungs of a ladder  A base from one strand pairs with a base from the other strand. The two bases face each other

18. Answer: Weak Hydrogen bonds that form between the pairs of bases. It is important that these bonds break’ Easily because DNA needs to ‘unzip’ in order to replicate before cell division!

19. Adenine pairs only Thymine(A – T) Guanine pairs only with Cytosine (G – C)

20. Notice: A Purine on one strand of DNA always pairs with a pyrimadine on the other strand. The structure and size of the nitrogen bases allow for this pairing arrangement only.

21. Base-pairing rules – the pairing arrangement of the nitrogen bases between the 2 strands This is supported by Chargaff’s observations.

22. The two strands of DNA that make up the double helix are complementary to each other. This means that the sequence of one strand determines the sequence of bases on the other strand.

23. Sample sequence of DNA on one strand: TCGAACT What is the sequence of DNA on the other strand?

24. Answer: AGCTTGA

25. Take two minutes to summarize what you have learned about the structure of DNA. Be sure to include the following in your summary Describe the SHAPE of the DNA molecule. Name the building block of DNA, along with its subcomponents. Describe how the molecule is held together.

27. http://video.nationalgeographic.com/video/sal mon_sockeye