2. Chapter 11: DNA & Genes Sections 11.1: DNA: The Molecular of Heredity Subsections: What is DNA? Replication of DNA

3. What is DNA? DNA as the genetic material Enzymes are critical for an organism’s function because they control the chemical reactions for life. DNA contains the information to produce proteins that make enzymes. Hershey & Chase: proved that DNA is the genetic material The structure of nucleotides DNA is composed of three parts: Phosphate group Sugar group (deoxyribose) Nitrogenous bases (4 types) Phosphate group and sugar group form the backbone of DNA molecule.

4. Section 11.1 Summary – pages 281 - 287 A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine (A) Guanine (G) Thymine (T) Cytosine (C) The structure of nucleotides What is DNA? 3Copyright BDOL 2006

5. What is DNA? The structure of DNA The importance of nucleotide sequences Four nitrogenous bases: Adenine Guanine Cytosyine Thymine Are attached by hydrogen and covalent bonds to opposite and adjacent nucleotides. Watson & Crick: Discovered the structure of DNA to be double stranded that form a helix shape hence double helix.

6. Section 11.1 Summary – pages 281 - 287 DNA is a polymer made of repeating subunits called nucleotides. Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base. Phosphate group Sugar (deoxyribose) Nitrogenous base The structure of DNA 5Copyright BDOL 2006

7. Section 11.1 Summary – pages 281 - 287 The importance of nucleotide sequences Chromosome The sequence of nucleotides forms the unique genetic information of an organism. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be. 6Copyright BDOL 2006

8. Replication of DNA How DNA replicates Interphase: Prior to mitosis and meiosis, the DNA replicates during the S phase of interphase. The DNA is copied to have Two sets of identical DNA. Refer to page 285 Figure 11.4. Copying DNA Refer to page 286- 287 Figure 11.5 DNA is copied prior to mitosis and meiosis.

9. Replication of DNA Part A: Separation of strands When a cell begins to copy its DNA, the two nucleotide strands of a DNA molecule separate when the hydrogen bonds connecting the base pairs are broken. As the DNA molecule unzips, the bases are exposed. Caused by an enzyme. Part B: Base Pairing The bases in the free nucleotides pair with exposed bases in the DNA strand. Thymine combines with adenine. Cytosine combines with guanine. All bases pairs have a hydrogen bonds to complete the pairing.

10. Section 11.1 Summary – pages 281 - 287 In DNA, the amount of adenine is always equal to the amount of thymine, and the amount of guanine is always equal to the amount of cytosine. Part B: Base Pairings 9Copyright BDOL 2006

11. Replication of DNA Part C: Bonding of bases The sugar (deoxyribose) and the phosphate parts of adjacent nucleotides bond together with covalent bonds (share electrons) to form the backbone of the new strand. Each original strand is now hydrogen-bonded to a new strand. Part D: Results of replication The process of replication produces two molecules of DNA. Each new molecule has one strand from the original molecule and one strand that has been newly synthesized from the free nucleotides in the cell.

12. Section 11.1 Summary – pages 281 - 287 Replication of DNA during S step the of cell cycle Click this image to view movie 11 Copyright BDOL 2006

13. Chapter 11: DNA & Genes Sections 11.2: From DNA to Protein Subsections: Genes and Proteins, RNA, Transcription, RNA processing, The Genetic Code, & Translation

14. Two Subsections: Genes and Proteins Refer to attachment or next slide. RNA Three differences Between RNA & DNA Three types of RNA Messenger – mRNA Ribosome – rRNA Transfer - tRNA

15. Section 11.2 Summary – pages 288 - 295 Some proteins become important structures, such as the filaments in muscle tissue. Other proteins, such as enzymes, control chemical reactions that perform key life functions—breaking down glucose molecules in cellular respiration, digesting food, or making spindle fibers during mitosis. Genes and Proteins 14Copyright BDOL 2006

16. Section 11.2 Summary – pages 288 - 295 RNA like DNA, is a nucleic acid. RNA structure differs from DNA structure in three ways. First, RNA is single stranded—it looks like one-half of a zipper —whereas DNA is double stranded. RNA: three difference compared to DNA 15Copyright BDOL 2006

17. Section 11.2 Summary – pages 288 - 295 Second, the sugar in RNA is ribose; DNA’s sugar is deoxyribose. Ribose RNA: three differences compared to DNA 16Copyright BDOL 2006

18. Section 11.2 Summary – pages 288 - 295 Third, both DNA and RNA contain four nitrogenous bases, but rather than thymine, RNA contains a similar base called uracil (U). Uracil forms a base pair with adenine in RNA, just as thymine does in DNA. Uracil Hydrogen bonds Adenine RNA: three differences compared to DNA 17Copyright BDOL 2006

19. Section 11.2 Summary – pages 288 - 295 There are three types of RNA that help build proteins. Messenger RNA (mRNA), brings instructions from DNA in the nucleus to the cell’s factory floor, the cytoplasm. In nucleus and cytoplasm. RNA: three types of RNA 18Copyright BDOL 2006

20. Section 11.2 Summary – pages 288 - 295 The ribosome, made of ribosomal RNA (rRNA), binds to the mRNA and uses the instructions to assemble the amino acids in the correct order. Located in cytoplasm only. RNA: three types of RNA 19Copyright BDOL 2006

21. Section 11.2 Summary – pages 288 - 295 Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein. Located in the cytoplasm only. RNA: three types of RNA Amino Acid Transfer RNA 20Copyright BDOL 2006

22. Section 11.2 Summary – pages 288 - 295 TranscriptionTranscription: copy DNA to mRNA TranscriptionTranscription: copy DNA to mRNA Click on Transcription for video 21Copyright BDOL 2006

23. Section 11.2 Summary – pages 288 - 295 Not all the nucleotides in the DNA of eukaryotic cells carry instructions— or code—for making proteins. Genes usually contain many long noncoding nucleotide sequences, introns called introns, that are scattered among the coding sequences. RNA Processing 22Copyright BDOL 2006

24. Section 11.2 Summary – pages 288 - 295 RNA Processing Regions that contain information are called exons because they are expressed. When mRNA is transcribed from DNA, both introns and exons are copied. 23Copyright BDOL 2006

25. Section 11.2 Summary – pages 288 - 295 Enzymes in the nucleus cut out the intron segments and paste the mRNA back together. The mRNA then leaves the nucleus nucleus and travels to the ribosome ribosome. RNA Processing 24Copyright BDOL 2006

26. Section 11.2 Summary – pages 288 - 295 Sixty-four combinations are possible when a sequence of three bases is used; thus, codons 64 different mRNA codons are in the genetic code. The Genetic Code 25Copyright BDOL 2006

27. Section 11.2 Summary – pages 288 - 295 The Genetic Code 26Copyright BDOL 2006 Table 11.1: The Messager RNA Gentic Code Page 292

28. Section 11.2 Summary – pages 288 - 295 Some codons do not code for amino acids; they provide instructions for making the protein. More than one codon can code for the same amino acid. However, for any one codon, there can be only one amino acid. The Genetic Code Copyright BDOL 2006

29. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein The process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation. Translation takes place at the ribosomes in cytoplasm the cytoplasm. In prokaryotic cells, which have no nucleus, cytoplasm the mRNA is made in the cytoplasm. Copyright BDOL 2006

30. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein In eukaryotic cells, mRNA is made in the nucleus and travels to the cytoplasm cytoplasm. cytoplasm In cytoplasm, a ribosome attaches to the strand of mRNA like a clothespin clamped onto a clothesline. Copyright BDOL 2006

31. Section 11.2 Summary – pages 288 - 295 Each tRNA molecule attaches to only one type of amino acid. Amino acid Chain of RNA nucleotides Transfer RNA molecule Anticondon The role of transfer RNA Copyright BDOL 2006

32. Section 11.2 Summary – pages 288 - 295 TranslationTranslation: mRNA to protein with rRNA & tRNA TranslationTranslation: mRNA to protein with rRNA & tRNA Click on Transcription for video 31Copyright BDOL 2006

33. Section 11.2 Summary – pages 288 - 295 Usually, the first codon on mRNA is AUG, which codes for the amino acid methionine. AUG signals the start of protein synthesis. When this signal is given, the ribosome slides along the mRNA to the next codon. The role of transfer RNA (tRNA) Copyright BDOL 2006

34. Section 11.2 Summary – pages 288 - 295 tRNA anticodon Methionine The role of transfer RNA mRNA codon Copyright BDOL 2006

35. Section 11.2 Summary – pages 288- 295 The amino acids are joined when a peptide bond is formed between them. Alanine Methionine Peptide bond The role of transfer RNA Copyright BDOL 2006

36. Section 11.2 Summary – pages 288 - 295 A chain of amino acids is formed until the stop codon is reached on the mRNA strand. Stop codon The role of transfer RNA Amino acid chain mRNA strand tRNA Copyright BDOL 2006

37. Section 11.2 Summary – pages 288 - 295 Follow the steps in Figure 11.9 page 294. Translating the mRNA code Copyright BDOL 2006

38. 11.2 Questions 1.List the three differences between RNA and DNA 2.List the three kinds or types of RNA include the location of each type within the cell. 3.Name the location of where transcription occurs. 4.What is the function of an intron? 5.What is the function of an exon?

39. 1. Name the three differences between RNA and DNA 1.RNA is single strand while DNA is double stranded – DNA is known as a double helix 2.RNA is composed of RIBOSE sugar with an extra oxygen while DNA is composed of DEOXYRIBOSE sugar with one less oxygen. 3.RNA has URACIL as a nitrogen base while DNA has THYMINE which both base pair with adenine.

40. 2. List the three types or kinds of RNA include the locations within the cell. 1.mRNA – messenger RNA is found in the nucleus and cytoplasm of the cell. 2.rRNA – ribosomal RNA is found in the cytoplasm of the cell. 3.tRNA – transfer RNA is found in the cytoplasm of the cell.

41. 3. Name the location of where transcription occurs. Transcription occurs in the nucleus of the cell.

42. 4. What is the function of an intron? An intron is the part of the DNA and mRNA that is noncoding. The intron is cut and removed from the mRNA before leaving the nucleus.

43. 5. What is the function of an exon? An exon is the part of the DNA and mRNA that is coded or codon. The exon is pasted together onto the mRNA before Leaving the nucleus.