1. DNA, RNA

2. Genes A segment of a chromosome that codes for a protein. –Genes are composed of DNA

4. Three Properties of Genes: They carry information from one generation to the next. They determine the inherited characteristics of the organism. They are easily copied because genetic information must be copied (replicated) every time a cell divides.

5. The Structure of DNA: DNA is a long molecule composed of nucleotide units. A nucleotide unit contains: –Deoxyribose sugar –Phosphate group –One of four nitrogen bases: Adenine Guanine Cytosine Thymine

7. The Structure of DNA is a Double Helix This was determined by Watson and Crick. Backbone of helix – sugar and phosphate molecules. Rungs of ladder – nitrogenous bases. The strands are held together by hydrogen bonds.

9. Chargaff’s Rule for Base Pairs: Adenine pairs with thymine. Cytosine pairs with guanine. Adenines = Thymines Cytosines = Guanines

10. Chromosomes in Prokaryotic Cells: Prokaryotic cells have no nucleus. They have one ring of DNA or RNA in the cytoplasm.

11. Chromosomes in Eukaryotic Cells: Eukaryotic cells have 1,000 times as much DNA as prokaryotes. It is packed tightly in the nucleus of the cell. DNA is a long molecule – the nucleus of a human cell contains 1 meter (3 feet) of DNA. Chromosomes are composed of DNA wrapped tightly around proteins called histones.

13. DNA Replication DNA must be copied before the cell can divide. The DNA molecule separates – each strand acts as a template for a new strand. This process results in two DNA molecules. Each molecule has one original strand and one new strand.

15. How is RNA different from DNA? DNA –Carries the recipe for the protein. –Double stranded. –Located in the nucleus. –Contains the sugar deoxyribose. –Contains the nitrogen bases cytosine, guanine, adenine and thymine.

16. RNA –Makes the protein from the recipe. –Single stranded. –Located in the cytoplasm. –Contains the sugar ribose. –Contains the nitrogen bases cytosine, guanine, adenine, uracil.

18. How much DNA do we have in our bodies? If all the DNA in your body was tied together, it would stretch to the sun and back 600 times!

19. Three Types of RNA mRNA – messenger RNA –A gene is a recipe for a protein –mRNA copies the recipe for the protein. –It carries a copy of these instructions from the nucleus to the cytoplasm.

21. rRNA – ribosomal RNA –Makes up the ribosomes.

22. tRNA – transfer RNA –Transfers amino acids that are coded for by the mRNA recipe from the cytoplasm to the ribosomes.

23. Protein Synthesis – Two Steps Transcription –The recipe is written (in the nucleus). Translation –The recipe is translated into the language of proteins (amino acids).

24. Transcription To transcribe means “to write”. DNA strands separate. One strand serves as a template and is copied by mRNA. The DNA recipe is written in 3 base segments called triplets. One triplet codes for one amino acid.

25. mRNA writes the recipe for a protein in its own language. In the language of RNA, C pairs with G, A pairs with U. This process takes place in the nucleus.

26. Proteins are composed of amino acids. The language of mRNA instructions is called the genetic code. Each word of the coded message is 3 bases long. This 3 base segment is called a codon. Each codon codes for one amino acid (20 amino acids).

28. Practice DNA triplets: –GGG – CCC – CGC – CTT – AGG – TAT What would the mRNA codons be for these triplets? Which amino acids would be specified for by these codons?

30. Translation To translate means to “change to another language”. The language of proteins is amino acids. mRNA attaches to the ribosomes with the recipe for the protein. The tRNA molecule with the anticodon to the mRNA codon brings the amino acid called for by the recipe to the ribosomes.

33. Amino acids are attached in a polypeptide chain until the recipe for the protein is complete. Translation takes place in the cytoplasm.

34. Practice Write the anticodons to the following codons: CGC – GGA – AAU – UAU – ACA - GAU

36. Why are proteins important? All enzymes are proteins. Every chemical reaction in the body requires an enzyme to make it go. Enzymes make some reactions go 1 million times faster than they would go without the enzyme. Proteins regulate the rate of growth of an organism.

37. Most structures in the body are made of proteins. –Muscles –Hair –Organs –Skin Proteins regulate the pattern of growth of an organism. Proteins are the key to almost everything living cells do.

38. Mutations A change in a gene or chromosome. Some mutations result in no change in the organism. A few mutations cause favorable changes in an organism. In humans, mutations usually cause harm. Cystic fibrosis, sickle cell anemia, Down’s syndrome.

39. Gene Mutations Point mutations – occur at a single point in the DNA sequence. Some point mutations simply substitute one nucleotide for another.

40. Frameshift mutation – results in a much bigger change because a nucleotide is inserted or deleted. Every amino acid that follows the point of insertion or deletion is affected.

41. Frameshift Mutations

42. Chromosomal Mutations Involve changes in the number or structure of chromosomes.

43. Human Genome Project The complete recipe list for all of the proteins needed to make a human. Our DNA contains more than a billion base pairs. The genome was mapped in 2000.

45. We were found to have about 20,000 genes that code for proteins. Worms have 19,098! Fruit flies have 13,602! Yeast has 6,023! Less than 2% of the genome actually codes for proteins. 97% of the genome has no known function (junk DNA).