Chapter 12 DNA and RNA.

Chapter 12 DNA and RNA

I. Structure of DNA Made up of Nucleotides (Parts) 1. Sugar 2. Phosphate 3. Nitrogen Base B. Four nitrogen bases 1. Adenine 2. Guanine 3. Thymine 4. Cytosine

C. Chargaff’s Rules = Base pairing Rules
1. A is found in equal amount to T and C is found in equal amount to G 2. Therefore, A = T and C = G D. X-Ray Evidence 1. Rosalind Franklin used X-Ray diffraction to take a picture of DNA E. Watson and Crick 1. Used Franklin’s picture of DNA to determine structure 2. Found out DNA is a double helix (twisted ladder)

DNA Double Helix

II. DNA-ANTI-Parallel Orientation
A. Prokaryotes DNA is located in cytoplasm 1. Single circular DNA B. Eukaryotes DNA is located in the nucleus 1. 1,000 X more DNA 2. DNA & protein (histones) = chromatin a. Form beadlike structure = nucleosome i. Helps fold long DNA to fit into the tiny space b. Chromatin tightly coiled up = chromosome

III. DNA Replication (Page 298)
A. DNA molecule produces 2 new complementary strands B. Starts at a single point (replication fork) and proceeds in two directions C. Helicase unwinds and “unzips” DNA (hydrogen bonds are broken between base pairs) D. Each strand serves as a template E. Free floating nucleotides attach to each template F. DNA polymerase (enzyme) proofreads new strands G. Each double-strand contains an old strand and a new strand of DNA- called SEMI-CONSERVATIVE REPLICATION

Page 298 New Strand Original strand Nitrogen Bases Growth Growth
Replication Fork Replication Fork DNA Polymerase

IV. RNA A. Single strand of nucleotides 1. Sugar = Ribose 2. Base pairing: a. Cytosine = Guanine b. Adenine = Uracil B. Types of RNA Carries instructions for making proteins from DNA to ribosome 1. Messenger RNA (mRNA): 2. Ribosomal RNA (rRNA): Helps assemble proteins- in ribosome 3. Transfer RNA (tRNA): Transfers amino acids to the ribosome

Transcription Page 301

V. GENE EXPRESSION Part I- Transcription (p. 301)
A. mRNA makes a copy from DNA – RNA Polymerase B. Starts at promoter site C. RNA nucleotides pair up with DNA to make mRNA D. mRNA leaves nucleus: Goes to ribosome E. TRANSCRIPTION = making mRNA from DNA

VI. Genetic Code – Triplet Code
A. Three bases read at a time = a “word” B. Codon = sequence of three bases on mRNA that codes for a specific amino acid 1. Four different letters used to code for 20 amino acids 2. 4 x 4 x 4 = 64 possible codons for 20 amino acids 3. A single amino acid may have many codons 4. Start codon = AUG = Methionine (amino acid) 5. Stop codon = UGA, UAA, or UAG

Translation Pages

Lysine Phenylalanine tRNA Methionine Ribosome mRNA Start codon

VII. GENE EXPRESSION Part II- Translation
A. Decoding of mRNA into protein (polypeptide chain) B. Begins when mRNA attaches to ribosome at start codon C. Each codon moves through ribosome and correct amino acid is brought to ribosome by tRNA 1. Anticodon on tRNA pairs with codon on mRNA 2. Anticodon = sequence of three bases on tRNA D. Peptide bond forms between amino acids E. mRNA moves through ribosome until stop codon F. New protein (polypeptide chain) and mRNA are released from ribosome

T A C A T G DNA Strand: A T G T A C mRNA Strand: A U G U A C
(From top DNA strand) tRNA bases = anticodon U A C A U G Amino Acids = Methionine - Tyrosine

Gene Expression 1. Transcription 2. Translation

VIII. Mutations A. Mutation = change in genetic material B. Gene Mutation = Change in a single gene 1. Point mutation = change in a single nucleotide a. Subsitution with no effect = no a.a change b. Substitution with effect = amino acid change = protein change

c. Frameshift Mutations
1. Insertion = one nucleotide is added 2. Deletion = one nucleotide is taken away 3. Shifts reading frame = change in amino acids down the chain

C. Chromosomal Mutations
1. Deletion = loss of part or entire chromosome 2. Duplication = a segment of chromosome is repeated

3. Inversion = part of chromosome becomes reversed
4. Translocation = part of one chromosome breaks off and attaches to another

12–1 Avery and other scientists discovered that
A. DNA is found in a protein coat. B. DNA stores and transmits genetic information from one generation to the next. C. transformation does not affect bacteria. D. proteins transmit genetic information from one generation to the next.

12–1 The Hershey-Chase experiment was based on the fact that
A. DNA has both sulfur and phosphorus in its structure. B. protein has both sulfur and phosphorus in its structure. C. both DNA and protein have no phosphorus or sulfur in their structure. D. DNA has only phosphorus, while protein has only sulfur in its structure.

12–1 DNA is a long molecule made of monomers called A. nucleotides.
B. purines. C. pyrimidines. D. sugars.

12–1 Chargaff's rules state that the number of guanine nucleotides must equal the number of A. cytosine nucleotides. B. adenine nucleotides. C. thymine nucleotides. D. thymine plus adenine nucleotides.

12–1 In DNA, the following base pairs occur:
A. A with C, and G with T. B. A with T, and C with G. C. A with G, and C with T. D. A with T, and C with T.

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12–2 In prokaryotic cells, DNA is found in the A. cytoplasm. B. nucleus. C. ribosome. D. cell membrane. Copyright Pearson Prentice Hall

12–2 The first step in DNA replication is A. producing two new strands. B. separating the strands. C. producing DNA polymerase. D. correctly pairing bases. Copyright Pearson Prentice Hall

12–2 A DNA molecule separates, and the sequence GCG AAT TCG occurs in one strand. What is the base sequence on the other strand? A. GCG AAT TCG B. CGC TTA AGC C. TAT CCG GAT D. GAT GGC CAG Copyright Pearson Prentice Hall

12–2 In addition to carrying out the replication of DNA, the enzyme DNA polymerase also functions to A. unzip the DNA molecule. B. regulate the time copying occurs in the cell cycle. C. “proofread” the new copies to minimize the number of mistakes. D. wrap the new strands onto histone proteins. Copyright Pearson Prentice Hall

12–2 The structure that may play a role in regulating how genes are “read” to make a protein is the A. coil. B. histone. C. nucleosome. D. chromatin. Copyright Pearson Prentice Hall

12–3 The role of a master plan in a building is similar to the role of which molecule? A. messenger RNA B. DNA C. transfer RNA D. ribosomal RNA Copyright Pearson Prentice Hall

12–3 A base that is present in RNA but NOT in DNA is A. thymine B. uracil. C. cytosine. D. adenine. Copyright Pearson Prentice Hall

12–3 The nucleic acid responsible for bringing individual amino acids to the ribosome is A. transfer RNA. B. DNA. C. messenger RNA. D. ribosomal RNA. Copyright Pearson Prentice Hall

12–3 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the A. intron. B. exon. C. promoter. D. codon. Copyright Pearson Prentice Hall

12–3 A codon typically carries sufficient information to specify a(an) A. single base pair in RNA. B. single amino acid. C. entire protein. D. single base pair in DNA. Copyright Pearson Prentice Hall

12–4 A mutation in which all or part of a chromosome is lost is called a(an) A. duplication. B. deletion. C. inversion. D. point mutation. Copyright Pearson Prentice Hall

12–4 A mutation that affects every amino acid following an insertion or deletion is called a(an) A. frameshift mutation. B. point mutation. C. chromosomal mutation. D. inversion. Copyright Pearson Prentice Hall

12–4 A mutation in which a segment of a chromosome is repeated is called a(an) A. deletion. B. inversion. C. duplication. D. point mutation. Copyright Pearson Prentice Hall

12–4 The type of point mutation that usually affects only a single amino acid is called A. a deletion. B. a frameshift mutation. C. an insertion. D. a substitution. Copyright Pearson Prentice Hall

12–4 When two different chromosomes exchange some of their material, the mutation is called a(an) A. inversion. B. deletion. C. substitution. D. translocation. Copyright Pearson Prentice Hall