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DNA What are genes made of? Where are genes located? How do they determine characteristics?

After reading this, try to answer the questions with your partner… Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.

Try to figure out what happened? Harmless Disease-causing Heat-killed Harmless & Heat- bacteria bacteria disease causing killed disease causing

Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Go to Section:

Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Go to Section:

Some History While Frederick Griffith was experimenting with pneumonia, he discovered that mice injected with dead bacteria still died of pneumonia… so it was something inside the bacteria that was still passed on to the next generation. Oswald Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

Some More History Alfred Hershey and Martha Chase concluded that the genetic material of the bacteriophage (a virus that “eats” bacteria) is DNA, not protein.

Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:

Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:

Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Go to Section:

DNA Genes are made of DNA = deoxyribonucleic acid How could DNA code for everything genes do? Genes had to carry information from one generation to the next Genes had to put that information to work by determining the inheritable characteristics of organisms Genes had to be easily copied, because it is replicated every time the cell divides

DNA’s Structure A long molecule made of units called nucleotides Each nucleotide is made of 3 basic parts: A 5-carbon sugar called deoxyribose A phosphate group A nitrogenous base (There are 4 kinds…) A (Adenine) T (Thymine) G (Guanine) C (Cytosine) Purines Pyrimidines

Figure 12–5 DNA Nucleotides Section 12-1 Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose Go to Section:

A Single DNA Nucleotide Phosphate Group Deoxyribose Sugar Nitrogenous Base

DNA Structure Phosphate Group Deoxyribose Sugar Nitrogenous Base Weak Hydrogen Bonds

Figure 12–7 Structure of DNA Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Go to Section:

The Chargaff “rule” It was discovered that the percentages of guanines (G) and cytosines (C) are almost equal and the percentages of adenines (A) and thymines (T) are almost equal Erwin Chargaff came up with a “rule” that guanine (G) pairs with cytosine (C) and adenine (A) pairs with thymine (T).

DNA Base Pairing Nitrogenous base pairs: Adenine (A) with Thymine (T) Guanine (G) with Cytosine (C)

Let’s pair up DNA! What would pair up with ATCG? TAGC What would pair up with ATTAGC? TAATCG What would pair up with ATACGGTC? TATGCCAG

The Double Helix Rosaline Franklin’s x-ray showed that two DNA strands are twisted around each other. James Watson and Francis Crick used Franklin’s x-ray to make a model of DNA. Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other. Watson and Crick also discovered that hydrogen bonding held the nitrogenous bases together.

Let’s wrap it up with a few questions together… 1. How many strands does DNA have? a. one b. two c. three d. four 2. Which scientists came up with the double helix model of DNA? a. Hershey & Chase b. Watson and Crick d. Darwin & Malthus c. Galileo & Aristotle

3. What holds the strands of DNA together? a. Phosphate Group b. Deoxyribose Sugar c. Hydrogen Bonds d. Nitrogen bonds 4. What DNA bases would pair up with CATTAT? a. CATTAT b. TATTAC c. GTAATA d. GUAAUA 5. What DNA bases would pair up with GAATCC? a. CTTAGG b. GAATCC d. GCCTCC c. CGGAGG

Is your answer the same as earlier… What are genes made of?