1. DNA The Genetic Code

2. Genes determine traits Genes are on chromosomes Genes are replicated and distributed to new nuclei by mitosis and meiosis

3. Fertilization produces a new organism having a particular combination of genes. This combination controls the new organisms traits.

4. What are genes made of ? DNA- deoxyribonucleic acid Found in the nucleus The chemical of heredity DNA is a complex molecule composed of 3 smaller parts. These parts are: 1.sugar (deoxyribose) 2. Phosphate group 3. 4 nitrogen bases

6. The 3 parts(sugar, Phosphate and 1 nitrogen base) combine to form subunits called Nucleotides. Many nucleotides join together to form a DNA molecule.

7. In DNA there are 4 different nitrogen bases They are: 1. Adenine 2. Guanine 3. Thymine 4. Cytosine

8. 1952 James Watson and Francis Crick determined DNA is built like a ladder (twisted) or double helix. This ladder “upright” (sides) of sugar, phosphate “rungs” (steps) of nitrogen bases Each rung contains 2 bases joined together by weak chemical bonds.

9. ***Base- Pairing Rule Only certain bases can bond with one another. Adenine always bonds with Thymine and Guanine always bonds with Cytosine ** “GCAT” The sequence of nucleotides in a DNA molecule is unique to all organisms: DNA code

10. *** Replication As chromosomes replicate during mitosis and meiosis, DNA is also replicated.

11. *** Another kind of nucleic acid, Ribonucleic Acid (RNA), RNA works along with DNA to carry out activities in the cell. Differences: 1. Single stranded 2. Sugar- ribose 3. Uracil base instead of thymine “GCAU”

12. Transcription * DNA stays in the nucleus How does info get to the rest of the cell? RNA * Transcription is the process of transferring the genetic code from DNA to RNA.

13. ** messenger RNA ( mRNA ) ** transfer RNA ( tRNA ) mRNA – carries protein synthesis info from DNA to the ribosomes. tRNA – delivers amino acids to the ribosomes for protein synthesis.

15. Practice Problems If you had 15% of guanine in a DNA molecule, how much cytosine would you have? 15%

16. If you had 15% guanine in a DNA molecule, how much adenine would you have? 15% G, 15% C = 30% So there’s 70% left, half adenine, half thymine So we have 35% adenine

17. DNA complementary base pair GCTAACGT Pairs with CGATTGCA You try one: ATAGGCGATG TATCCGCTAC

18. DNA to mRNA transcription Transcription: mRNA (“GCAU”) DNA: CGG ATA CGA TAG mRNA: GCC UAU GCU AUC Remember there is no thymine in RNA therefore we substitute uracil We break into groups of 3, triplets in DNA then mRNA group of 3 is a codon

19. mRNA to tRNA translation We have our codon of RNA, we now go to an anticodon (group of 3) for tRNA mRNA: GCC UAU GCU AUC tRNA: CGG AUA CGA UAG

20. Reading the Codon chart mRNA: GCC UAU GCU AUC Look in first base column, find G then 2 nd base C then 3 rd base C Then amino acid that pairs with it: Ala Go through this with each codon