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DNA and Genes Q: How do genes work? How do genes determine your characteristics? What are genes made of? Genes: Portions of DNA that contain the instructions for producing traits **How does DNA produce traits? By producing proteins All body structures, skin, muscles and bones are made of proteins Enzymes, also proteins, are critical for organ function and chemical reactions A. DNA (Deoxyribo Nucleic Acid) Polymer made of many nucleotides 1. Nucleotide: monomer for nucleic acids; 3 parts Sugar: deoxyribose Phosphate Nitrogen base (4 different) a. Adenine (A) b. Thymine (T) c. Cytosine (C) d. Guanine (G) Many of these nucleotides bond together between the nitrogen bases and between a phosphate group of one nitrogen base and the sugar of the next to form a double helix Adenine (A) and Thymine (T) always pair together; Cytosine (C) and Guanine (G) always pair together Double Helix: twisted ladder, shape of DNA Backbone: phosphate and sugar (deoxyribose) ½ rung/step: Nitrogen base (ATGC) Weak H bonds hold the two halves of the ladder together From DNA to Proteins Background Info: 1. DNA is located in the nucleus and stays in the nucleus 2. Must make a partial copy of itself that will leave the nucleus and go the ribosome (site of protein production) 3. Ribosome reads the information and constructs the proteins according to the code A. RNA (Ribo Nucleic Acid) Polymer made of many nucleotides RNA Nucleotides: 3 parts 1. sugar: Ribose 2. Phosphate 3. Nitrogen Base: a. Adenine (A) b. Uracil (U) c. Cytosine (C) d. Guanine (G) Structure of RNA: single stranded 1. 3 Types of RNA a. mRNA (messenger RNA) carries the information/carries the message from the DNA (located in the nucleus) to the ribosomes contains Codons: 3 nucleotides in a row that represent an amino acid Ex. UUU = phenylalanine CUG = leucine ACG = threonine b. rRNA (ribosomal RNA) is the actual ribosome (ribosomes are made of nucleic acids) reads the mRNA and uses it to assemble proteins c. tRNA (transfer RNA) transports amino acids within the cytoplasm to the ribosome to assemble proteins in the order according to mRNA Anticodon: 3 nucleotides on the tRNA that match up with the condon on mRNA and drop off/release the amino acid in the correct position; ensures that amino acid is the correct one B. DNA Replication When does DNA replicate? Mitosis and Meiosis: making new cells How does DNA replicate/copy itself? 1. Untwists: The double helix becomes untwisted 2. Unzips: enzymes break the hydrogen bonds between nitrogen bases; leaves nitrogen bases unpaired on both sides of the ladder 3. Fill in the empty spaces: complementary nucleotides (DNA) (AT/CG) that are floating around in the cytoplasm pair up forming 2 new strands of DNA C. DNA Transcription The process in which DNA is used to write out a portion of the code in the form of mRNA DNA is the template (serves as a pattern) for making mRNA Steps: similar to DNA replication 1. Untwist: double helix (DNA) untwists 2. Unzips: enzymes break the hydrogen bonds between complementary nucleotides causing the 2 strands of DNA to separate 3. Fill in the spaces: Complementary RNA nucleotides bind to one of the single DNA strands and then releases from the DNA, leaving the nucleus, and heading to the ribosome to make the protein 4. DNA twists back up again DNA 1st Strand A C G T T C A C G T A mRNA U G C A A G U G C A U DNA 2nd Strand T G C A A G T G C A T ***Note: (U) uracil pairs up with (A) adenine, not (T) thymine If (T) thymine is on DNA the complementary base is still (A) adenine ***Hint: when using the first strand of DNA to make mRNA, copy the second strand of DNA in order, but replace (T) thymine with (U) uracil D. RNA Translation (Protein Synthesis) Converting the code in mRNA to amino acids that make up proteins It’s the sequence/order of nitrogen bases on DNA that determine the protein synthesized Translation takes place at the ribosome Each codon on the mRNA represents an amino acid The tRNA brings the amino acid to the ribosome and temporarily binds its anticondon with the mRNA condon to ensure the amino acid belongs in that position mRNA Codon A U C 1. 2. 3. G G A Codon (mRNA) A U G G G A U U A U U A C A U Anticodon (tRNA) U A C C C U A A U Use a codon chart to look up the amino acids Amino Acid Methionine (start) Glycine Leucine Q: If all cells contain the same genetic information (46 chromosomes) why do they have different structures and functions? A: Only certain parts of the DNA become activated within those cells 46 chromosomes genes codons/amino acids proteins Cookbook recipe ingredients list product E. Genetic Changes 1. Mutations: any change in the DNA sequence Remember the sequence of nucleotides determines the necessary proteins If the nucleotide sequence changes due to a mutation the incorrect protein will be made Causes of mutation: radiation, chemicals, carcinogens, pollutants, spontaneous a. Mutations in Gametes: If the nucleotide sequence changes in the DNA of an egg or sperm cell that change will be passed on to future generations of offspring b. Mutations in Body Cells: If the nucleotide sequence changes in the DNA of a body cell it will not be passed on to the offspring These mutations may impair the function of that particular cell 2. Types of Mutations in DNA a. Point Mutation (Substitution): one nitrogen base changes = only one amino acid changes b. Frameshift Mutation: the addition or deletion of a nitrogen base Nucleotides shift over and all amino acids are changed after the deletion or addition c. Chromosomal Mutations: entire portions of DNA are deleted, inserted, inversed (backwards), translocated