DNA Genes were known to… Carry information from one generation to the next Genes determined the heritable characteristics (phenotypes) of organisms Genes had to easily be copied

Figure 12–5 DNA Nucleotides Section 12-1 Nitrogen Bases 20- 23 Purines Pyrimidines Adenine Guanine Cytosine Thymine Nucleotide Sugar Phosphate Group Nitrogen Base Phosphate group Deoxyribose Sugar Go to Section:

Figure 12–7 Structure of DNA Section 12-1 Nucleotide 24. Bases paired A-T…G-C Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Go to Section:

Chargaff’s Rule – Base Pairing Rule 25. Chargaffs rule- Chemical analysis showed that percent of A was equivalent to T and G was equivalent to C Source of DNA A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.8 27.5 22.2 22.6 Human 30.9 29.4 19.9 19.8 % of A ≈ % of T % of G ≈ % of C

Rosalind Franklin X Ray diffraction 26. Shaped is helix containing two strands

Watson and Crick Model 27-28 1953

Section Outline 12–2 Chromosomes and DNA Replication A. DNA and Chromosomes 1. DNA Length 2. Chromosome Structure B. DNA Replication 1. Duplicating DNA 2. How Replication Occurs Go to Section:

Prokayrotic vs. Eukaryotic DNA 1-3

Prokaryotic Chromosome Structure Section 12-2 5 Chromosome E. coli bacterium Bases on the chromosome Go to Section:

How DNA is packaged 3-4

Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Human cells contain over one meter of DNA! How? Nucleosome 7-10 Chromosome DNA double helix Coils Supercoils Histones Wrapped around proteins (histones and nucleosomes) – only in this prior to cell division (mitosis) as a way to package all that material Go to Section:

Figure 12–11 DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand Replication Go to Section:

DNA replication

Interest Grabber Information, Please Section 12-3 Information, Please DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out. 1. Why do you think the library holds some books for reference only? 2. If you can’t borrow a book, how can you take home the information in it? 3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell? Go to Section:

Section Outline 12–3 RNA and Protein Synthesis A. The Structure of RNA B. Types of RNA C. Transcription D. RNA Editing E. The Genetic Code F. Translation G. The Roles of RNA and DNA H. Genes and Proteins Go to Section:

RNA vs. DNA GR 1 Differences between RNA and DNA DNA contain deoxyribose sugar, RNA contains ribose DNA is double stranded and RNA is single RNA contain Uracil in place of Thymine

Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) GR 2 RNA is like disposable copy of DNA Hundreds of copies of RNA made from One strand of DNA RNA polymerase DNA RNA Go to Section:

RNA GR 5 tRNA – transfer RNA mRNA – messenger RNA Carries amino acid to the ribosome to assemble protein mRNA – messenger RNA Carries copy of instruction for proteins from DNA to the ribosomes

Bring amino acids to ribosome Concept Map Section 12-3 RNA can be Messenger RNA Transfer RNA also called which functions to also called which functions to Bring amino acids to ribosome mRNA Carry instructions tRNA from to DNA Ribosome Go to Section:

Figure 12–14 Transcription Section 12-3 Transcription – process by which DNA code is changed into mRNA Mr. Krabbs giving secret formula to Squidward to take to kitchen Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA Go to Section:

protein synthesis

Figure 12–17 The Genetic Code Section 12-3 Go to Section:

Figure 12–18 Translation Section 12-3 mRNA Go to Section: Nucleus Messenger RNA Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon Go to Section:

Figure 12–18 Translation (continued) Section 12-3 The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome Go to Section:

Interest Grabber Determining the Sequence of a Gene Section 12-4 Determining the Sequence of a Gene DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations. Go to Section:

Interest Grabber continued Section 12-4 1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. 2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. 3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. 4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5. Did this single deletion cause much change in your protein? Explain your answer. Go to Section:

Section Outline 12–4 Mutations A. Gene Mutations Section 12-4 Go to Section:

Mutations – any change in genetic material Gene mutations Chromosomal Changes to bases making up the gene Point – affect only 1 amino acid Substitution – a change in one base Frameshift – affect all amino acids from the mutation Deletion – removal of base Insertion – addition of base Changes to entire chromosome

Gene Mutations: Substitution, Insertion, and Deletion Section 12-4 Frameshift Point Deletion Substitution Insertion Notice only 1 amino acid changed Less impactful? Notice all amino acids are affected from the point of the mutation Go to Section: