DNA life s code. Importance of DNA. DNA Structure. DNA Structure - nucleotide. DNA Structure nitrogen bases. Linking Nucleotides

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1 Importance of life s code molecule that makes up genes and determines the traits of all living things Controls by: producing proteins Proteins are important because All structures are made of protein Skin Muscles Bones All actions depend on enzymes (special kind of protein) Eating Running Thinking All life activities Structure contains the complete instructions for making all proteins Structure Stands for deoxyribonucleic acid Double helix = twisted ladder = linked nucleotides Structure - nucleotide Made of 3 things: Deoxyribose Phosphoric acid Nitrogen bases Structure nitrogen bases Four types: Adenine Cytosine Guanine Thymine Linking Nucleotides Nucleotides join together to make complementary base pairing Adenine fits with Thymine A T Cytosine fits with Guanine C G A nucleotide is named for the nitrogen base it contains 1

2 How is packaged Figure Chromosome Structure of Eukaryotes Human cells contain over one meter of! How? Section 12-2 Chromosome Nucleosome Coils double helix Supercoils Histones Wrapped around proteins (histones and nucleosomes) Section Interest 12-2 Grabber A Perfect Copy When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the code. Before a cell can divide, the must be copied so that there are two sets ready to be distributed to the new cells. Section Interest 12-2 Grabber continued 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of that are given to new daughter cells be exact copies of the original? Section 12-2 Outline 12 2 Chromosomes and Replication A. and Chromosomes 1. Length 2. Chromosome Structure B. Replication 1. Duplicating 2. How Replication Occurs Replication Making a chromosome copy One strand two identical strands Steps: unzips Free nucleotides attach to complementary bases Bonds form between nucleotides creating two identical strands 2

3 Section Figure Replication New strand Original strand replication mat/molgenetics/dna-rna2.swf Growth Growth Replication fork Replication fork Nitrogenous bases New strand Original strand vs. 12/animations.asp Concept Map Section 12-3 Messenger also called which functions to also called which functions to from to can be m Carry instructions t Transfer Bring amino acids to ribosome Protein Synthesis Make proteins Two steps: Transcription: copying your (genes) into messenger (m). : turning messenger (m) into proteinsproteins make up cells. 3

4 Section 12-3 Transcription Adenine ( and ) Cystosine ( and ) Guanine( and ) Thymine ( only) Uracil ( only) Section 12-3 The Genetic Code Messenger Messenger is transcribed in the nucleus. Nucleus Methionine Phenylalanine t Lysine m Transfer The m then enters the cytoplasm and attaches to a ribosome. begins at AUG, the start codon. Each transfer has an anticodon whose bases are complementary to a codon on the m strand. The ribosome positions the start codon to attract its anticodon, which is part of the t that binds methionine. The ribosome also binds the next codon and its anticodon. m Start codon : : (continued) Transcription The Polypeptide Assembly Line The ribosome joins the two amino acids methionine and phenylalanine and breaks the bond between methionine and its t. The t floats away, allowing the ribosome to bind to another t. The ribosome moves along the m, binding new t molecules and amino acids. Lysine t t Growing polypeptide chain Splits In nucleus Unzipping Messenger (m) copies and reforms ladder m direction m Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Transfer (t) copy m and make proteins Travels to ribosome 4

5 Transcription Animation Gene Mutations: Substitution, Insertion, and Deletion Section 12-4 Substitution Insertion Deletion Point mutation- mutations that affect one nucleotide; generally change one amino acid in a protein (ex: substitution) Frameshift mutations (Insertion and Deletion) cause much bigger changes since the sequence is read in 3 base codons, everything is now moved over one spot Section 12-4 Figure Chromosomal Mutations Typical Gene Structure Section 12-5 Deletion Regulatory sites Promoter ( binding site) strand Duplication Start transcription Stop transcription Inversion Translocation - Involve changes in the number or structure of chromosomes - May change the location of genes and even the number of copies of some genes A typical gene includes start and stop signals, with the nucleotides to be translated in between 5