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DNA, RNA, Protein synthesis, and Mutations Chapters 12-13.3 1A)Identify the components of DNA and explain its role in heredity. • DNA’s • Role in heredity: Contains the genetic information of a cell that can be: • Stored • Ion transport • movement • Cell growth • Respiration • Copied • Copy genetic information before a cell divides • Transmitted • After cell division-each cell has a identical copy of information 1A)Identify the components of DNA and explain its role in heredity. DNA (Deoxyribonucleic acid)Structure of DNA 1. polymer made of nucleotides (Monomer) • deoxyribose sugar • phosphate group • nitrogen-containing base • Nucleotides join by covalent bonds • Nitrogen bases: make one nucleotide different from another •1A)Identify the components of DNA and explain its role in heredity. 2. Bases purines 2 Nitrogen rings adenine (A) guanine (G) IN DNA: pyrimidines 1Nitrogen ring in cytosine (C) thymine (T) RNA cytosine (C) Uracil (U) 1B)What is the importance of hydrogen bonds? 3. complementary base pairing C-G and A-T connected by hydrogen bonds weak bonds C and G have 3 A and T have 2 1C) Describe the discoveries that led to the modeling of DNA. • Chargaff’s Rule Discovered that the % of A and T were almost the same • Same as C & G • Therefore he concluded that: • •A pairs with T • C pairs with G 1C) Describe the discoveries that led to the modeling of DNA. Double helix model • Watson and Crick proposed by double helix model- 1953 • 2 nucleotide chains that wrap around each other (like a spiral staircase) • inspired by x-ray photograph of DNA crystals by Rosalind Franklin Shows twisted DNA-Helix • sugar on outside • N-bases in the center • http://www.pbs.org/wnet/dna/episode1/# • 1C) Describe the discoveries that led to the modeling of DNA. Ladder model: sides – • alternating deoxyribose sugar and phosphate rungs – • nitrogen bases attached to deoxyribose sugar • • hydrogen bonds hold two half ladders together • • • purine always attached to a pyrimidine between H and an O or an N atom nucleotide sequence of one half is exact complement of other half (Anti-parallel) http://www.youtube.com/watch?v=qy8dk5 iS1f0&feature=related 1D) Explain the events of DNA replication. occurs in the Nucleus 1. process of copying DNA in a cell 2. enzymes called helicases break H bonds and 2 sides separate 3. DNA polymerase enzyme assembles new DNA half using nucleotides found in nucleus 4. each half serves as a template (pattern) to make a new half 5. two exact copies of original DNA produced (due to complementary nature of nucleotides) • • • DNA polymerase also “proofreads” each new DNA strand, ensuring that each molecule is a perfect copy of the original each has one old and one new half 2A.) Compare and contrast DNA and RNA. DNA RNA • • • • Ribonucleic acid Ribose sugar Bases: A,U,C,G • uracil replaces thymine Single strand • • • • Deoxyribonucleic acid Deoxyribose sugar Bases: A,T,C,G Double Strand 2B.) What is the role of the three types of RNA? messenger RNA (mRNA) • carries genetic Ribosomal information from RNA (rRNA) DNA to • makes up cytoplasm ribosomes (ribosome) transfer RNA (tRNA)• binds to specific amino acids • Cloverleaf shape 2C)Explain the steps of transcription. 1. process where genetic info. is copied from DNA to RNA • • • DNA is blueprint for all proteins proteins made at ribosomes DNA can’t leave nucleus RNA polymerase (transcription enzyme) binds to promoter (beginning of a single gene) • Gene- small section of a chromosome that determines a specific trait) 2. DNA section (gene) separates 3. RNA polymerase attaches to DNA nucleotide and adds complementary RNA nucleotide 4. continues till RNA reaches termination signal (marks end of gene) 5. mRNA leaves nucleus 3A) Explain the steps of protein synthesis. Proteins • 1. polymers made of polypeptides Polypeptides made of amino acids (monomers) • Amino acids are connected by peptide bonds (C-N bond) • • 2. 20 amino acids 3B)Analyze the genetic code to determine codon and anticodon relationships. The Genetic Code 1. sequence of 3 mRNA nucleotides that code for an amino acid 2. codon - sequence of 3 mRNA bases that code for a specific amino acid • start codon • AUG(methionine) • stop codon – • UAA, - starts translation UAG, UGA- cause translation to stop 3A) Explain the steps of protein synthesis. Translation: • assembling amino acids from mRNA code • tRNA transports amino acids to ribosome • • opposite to the amino acid attachment site is sequence of 3 bases complementary to a specific codon called the ANTICODON • • • region that binds to specific amino acid insures that amino acids added in order prescribed by mRNA ribosomes (free and attached) have one binding site for mRNA and two for tRNA ribosome attaches to start codon and moves along to each codon until stop codon reached • • matching of anticodon and codon causes amino acids to join previous one and form peptide bond several ribosomes may translate same mRNA 3A) Explain the steps of protein synthesis. Translation: 4A) What is a mutation? • mutation a change in the nucleotide sequence • Latin word mutare, meaning “to change.” • 4B) Explain the difference between gene mutations and chromosomal mutations. Two basic categories of mutations: 1. gene mutations • produce changes in a single gene 2. chromosomal mutations. • produce changes in whole chromosomes 4C) Explain the different gene mutations. Point Mutations: Mutations that involve changes in one or a few nucleotides • occur at a single point in the DNA sequence • generally occur during replication. • If a gene in one cell is altered • • the alteration can be passed on to every cell that develops from the original one • 3 types: • Substitution • Insertion • Deletion 4C) Explain the different gene mutations Substitutions: •one base is changed to a different base. •usually affects no more than a single amino acid, and sometimes they have no effect at all 4C) Explain the different gene mutations Insertion • A nucleotide is added to DNA sequence Frameshift mutations: • shifts the “reading frame” of the genetic message • can change every amino acid that follows the point of the mutation • can alter a protein so it is unable to perform its normal functions. • Both insertion and deletions are framshift Deletions • A nucleotide is deleted to DNA sequence 4D) Describe the different chromosomal mutations. Deletion involves the loss of all or part of a chromosome. Duplication produces an extra copy of all or part of a chromosome Inversion reverses the direction of parts of a chromosome Translocation occurs when part of one chromosome breaks off and attaches to another. 4E) Explain 3 effects mutations can have on genes. Mutagens • chemical or physical agents in the environment that cause mutations. • Chemical mutagens: • certain pesticides, a few natural plant alkaloids, tobacco smoke, and environmental pollutants. • Physical • mutagens: some forms of electromagnetic radiation, such as X-rays and ultraviolet light. 4E) Explain 3 effects mutations can have on genes. If these mutagens interact with DNA, they can produce mutations at high rates: Some compounds interfere with base-pairing, increasing the error rate of DNA replication. • Others weaken the DNA strand, causing breaks and inversions that produce chromosomal mutations. • Cells can sometimes repair the damage; but when they cannot, the DNA base sequence changes permanently. • 4F) Why are mutations important? HARMFUL • • • Can create defective proteins that disrupt normal biological activities (genetic disorders). Causes some cancers due to uncontrolled growth of cells. Example of point mutation: • Sickle cell disease • is a disorder associated with changes in the shape of red blood cells. • Normal red blood cells are round. • Sickle cells appear long and pointed. • Causes anemia, severe pain, frequent infections, and stunted growth. BENEFICAL • • • • helped many insects resist chemical pesticides. enabled microorganisms to adapt to new chemicals in the environment. Polyploidy • an organism has extra sets of chromosomes Polyploidy plants are often larger and stronger than diploid plants. • bananas and limes • naturally in citrus plants, often spontaneous mutations.