Chapter 11: Understanding

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• Chapter 11 Understanding
• DNA

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CHAPTER 11 DNA AND GENES LEARNING OBJECTIVES

• In addition to reading this material , you are
  expected to do all of the Section Assessment
  questions, as well as all of the Chapter 11
  Assessment Questions, and the Standardized Test
  Practice in your textbook
• We will do a project related to this chapter.
  You will research and prepare a brief biography
  for one individual who contributed to our current
  knowledge of DNA or Heredity. This will be due
  on Tuesday, Feb 27. To create a class Timeline of
  DNA Discoveries.
• Be familiar with those scientists that largely
  contributed to discovering the structure and
  nature of DNA.
• Understand the structure of DNA, its components,
  bonds.
• Be able to describe DNA replication
• Be able to describe the significance of the
  nucleotide sequence between organisms.
• Be able to describe ways that nucleotide
  sequencing is useful to scientists and you
• Be able to sequence the steps in protein
  synthesis
• Be able to distinguish between different types of
  mutations
• Be able to describe the effect of genetic
  mutations
• Be able to describe the causes of mutations

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..\My Videos\NOVA Online Cracking the Code of
Life Watch the Program Here.htm

• ..\..\all biology\Nova

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UNDERSTANDING DNAHistory of Research

• Mendel 1860s--traits passed parent to offspring
• Others set out to identify the substance
  responsible

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Transformation-Genetic material could be
transferred to another organism

• 1928 Fredrick Griffith
• Discovers that Genetic material could be
  transferred to another organism
• Transformation Process by which bacteria takes
  up foreign DNA
• Non-Virulent bacteria become Virulent (disease
  causing)
• Descendents of the transformed cells also
  virulent.

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Transformed bacteria
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1.Infected with non- virulent bacteria
3. Mice infected with heat-killed bacteria.
4.Infected with live, nonvirulent AND heat-killed
bacteria. Mouse dies FROM TRANSFORMED BACTERIA
2. Mice infected with live, virulent bacteria.
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Oswald Avery (1944) Protein or DNA?DNA is the
Genetic material.

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Oswald Avery

• Protein vs. DNA?
• Did same type of experiments as Griffith, but
  treated with protein and DNA-digesting enzymes.
• RESULTS Treatment with protein-digesting
  enzymes-- bacteria still transform
• Treatment with DNA-digesting enzymes-not
  able to transform
• Concluded that DNA, not protein, transforms
  bacteria

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1952 Hershey Chase Reconfirm DNA is the
Genetic Material. They Infected bacteria with
Labeled Viruses (radioisotopes of Sulfur and
Phosphorous)(protein contains sulfur DNA
contains Phosphorous)
virus particle labeled with 35S
virus particle labeled with 32P
bacterial cell (cutaway view)
label outside cell
label inside cell
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Hershey and Chase

• The virus protein coat was outside the bacteria,
  but not inside any of the new viruses formed.
• Found the labeled DNA (phosphorous) inside the
  new virses and the bacteria.

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Structure of the Hereditary Material Still Was
a Mystery

• 1953 Nobel Prize
• James Watson Francis Crick
• Maurice Wilkins

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Watson Crick Developed Accurate Model

• Double helix shape
• Two strands of nucleotides
• Like a spiral staircase

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Watson-Crick Model

• 2 Strands of nucleotides
• Sugar and phosphates covalently bonded to one
  another.
• 2 Strands held together by
• hydrogen bonds between bases (rungs on a
  ladder)

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Shape of a double helix

• Twisted like a coiled spring.
• The molecule coils into this
• shape as a result of the
• base bonding.

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Rosalind Franklins Work was Critical

• Expert in x-ray images
• DNA was some sort of helix-like a tightly coiled
  spring

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Structure

• DNApolymer of nucleotides (4)
• Nucleotides
• Sugar (deoxyribose)
• Phosphate
• Nitrogen base
• Forms 2 long parallel chains
• of nucleotides
• covalently bonded (chains)
• Sugar to -phosphate

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• Phosphate-sugar-phosphate-sugar-phosphate..

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• The sugars and phosphates are held together by
  strong covalent bonds.
• The bases hold the 2 strands together
• The bases are held together by HYDROGEN BONDS(
  WEAK).
• They form the rungs of the ladder-like shape.

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DNA Structure

• 2 strands of nucleotides
• Nucleotides bond (strong-covalent
• bonds) together to form 2
• long chains
• Each chain connected in the
• middle by (weak) hydrogen bonds

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DNA-Made of 4 different. Nucleotides (

• Nucleotides have 3 parts
• 1 A sugar-deoxyribose
• 2. Phosphate Group
• 3. A Base (4 kinds)
• (draw and color in
• your notes)

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4 different nitrogeneous bases

• C cytosine
• T thymine
• A adenine
• G guanine

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Pattern of Base Pairing

• Chargaff s Rule (1949)
• Amount of adenine always equals amount of thymine
  and amount of guanine always equals amount of
  cytosine
• AT and GC

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Base Pairing

• C with G
• A with T
• ALWAYS TRUE

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DNA in cells

• Where is it found?
• Does it leave?
• Why/why not?
• Does a cell ever need to make more DNA?
• Why?
• When?

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Base Pairing
or
or
one base pair
in-text, p. 195
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The Importance of Nucleotide Sequences

• All organisms DNA made of the same 4 bases
• Vary in the
• Sequence of the bases
• Amount of DNA
• The closer the relationship, the more similar the
  DNA sequences.
• Useful
• Determine evolutionary relationships
• Determine whether 2 people are related
• Crime scene investigation

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NAME______________ DNA QUIZ

• 1. Nucleotides are the ________from which the
  Nucleic Acid polymers DNA and RNA are
• 2.What is Chargoffs rule?________________________
  _____________
• 3. Who constructed the first accurate model of
  DNA?___________________________
• 4. List the three parts of a DNA nucleotide
• 1.
• 2.
• 3.
• 5 _______________is the process by which
  bacteria takes up foreign DNA
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• 56 Nucleotides link together to form 2 sides of
  the DNA molecule ( like 2 sides of a ladder). The
  sugars and phosphates are held together by strong
  _____________bonds.
• 7. The bases hold the 2 strands together. The
  bases are held together by weak
  ________________bonds.
• 8. _________________are viruses that infect
  bacteria.
• 9. How does the DNA in YOU differ from the DNA in
  a tomato plant?
• (choose a or b)
• A) in tomato plants there are different
  nucleotides
• B) In tomato plants, the nucleotides are
  assembled in a different way, but using the same
  4 nucleotides as in people

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Problem Solving Lab 11.1 page 283
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WE WILL BEGIN CONSTRUCTING A DNA MOLECULE-need 8
different colored pencils and plain paper.

• Color code
• Phosphate yellow
• Sugar pink
• Covalent Bondspurple
• Hydrogen Bonds pencil
• Adeninegreen
• Thyminered
• Guanine orange
• Cytosineblue
• Make 2 chains of P-S-P-S (20/each long)
• (covalent bonds).
• Leave 2 inches between the 2 strands.

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Replication of DNA
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DNA in cells

• Where is it found?
• Does it leave?
• Why/why not?
• Does a cell ever need to make more DNA?
• Why?
• When?

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Discussion questions

• What if DNA was not replicated BEFORE MITOSIS?
• What if DNA was not replicated BEFORE MEIOSIS?

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Look at Figure 11.4

• When a DNA molecule replicates, 2 molecules are
  formed.
• DNA replication produces _____ molecules from
  one.
• Each molecule has one original strand, and one
  new strand.
• Please draw the first 2 steps of fig 11.4 in your
  notesuse 2 colors.
• Why are you using 2 colors??

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DNA REPLICATION-THE PROCESS OF COPYING DNA

• Preserves the sequence of bases in an organisms
  DNA
• There are basically 2 steps

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HOW DNA IS COPIED
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new
new
old
old
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First Step Replication bubble forms An
enzyme breaks the hydrogen bonds between
bases. Unzips a section of the double helix,
exposing the bases.
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Step Second

• DNA polymerase (an enzyme) moves along the 2
  strands, pairing complementary bases to the
  exposed nucleotides

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one parent DNA strand
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• This process continues until the entire DNA
  molecule has unzipped and been copied.
• WHY MUST DNA BE UNZIPPED BEFORE IT CAN BE COPIED?

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DNA REPLICATION

• Result is 2 identical DNA molecules.
• Semi-conservative

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Replication-recap

• The 2 original strands serve as templates for 2
  new strands.
• Follow base-pairing of Chargaffs rule.
• Two complete DNA molecules result from
  replication.

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Relication preserves the sequence of bases in
organisms DNA.
new
new
old
old
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Problem to do

• If the sequence of nitrogenous bases on one
  strand of a DNA molecule is
• CCGAATGATTTG
• What would be the sequence of bases on the
  complimentary strand?

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Take out the DNA strand you began constructing
earlier.
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new
new
old
old
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Base Pairing During Replication

• Each old strand serves as the template for
  complementary new strand

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Using DNAWhat was (is) the molecular cause of
Lorenzos disease?

• DNA Contains instructions for making proteins.
• Recall that proteins are built on __________IN
  THE CYTOPLASM.
• So how can we accomplish the protein building
  task?

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Mutation-An alteration in DNA structure

• May result from
• 1. Errors during replication
• OR
• 2. Mutagens an environmental agent

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Genes

• Segment of DNA that controls protein production.
• The specific nucleotide sequence is a recipe
  for a particular protein.

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• AS YOU ENTERGET YOUR PAPER DNA MODEL

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Section 11.2 DNA to Protein

• DNA controls cells
• HOW?
• Encoding instructions for making proteins
• Proteins and their functions
• Structural muscles, hair
• Enzymes control chemical reactions in organisms
• Cellular respiration, photosynthesis, digesting
  food, controlling cell cycle

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RNA is the link (lets make a double bubble using
RNA and DNA)

• A nucleic acid
• Single stranded molecule
• Sugar is RIBOSE
• Polymer
• Monomers are nucleotides
• C, U, A, G
• UUracilit replaces Thymine
• U base pairs with _________
• 3 kinds of RNA
• Carry out the job of protein assembly

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Sequence in DNA

• Contains information
• To make proteins

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Roles of protein

• Structural
• Enzymes
• Cell Membranes-transport molecules
• Hormones

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Proteins

• Polymers of _____ _______
• The sequence of _________in each gene contains
  information for the assembling the string of
  _______ ______ that make up a single ________

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RNA

• Nucleic acid
• Single stranded
• Ribose
• Uracil ( in place of T)

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Nucleotide Base Comparison

• DNA
• Cytosine
• Guanine
• Adenine
• Thymine

• RNA
• Cytosine
• Guanine
• Adenine
• Uracil

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An analogy DNA Project Engineer RNAs
The workers. Production site
ribosomes Product proteins

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3 types of RNA

• 1. mRNA a gene is transcribed into a
  messenger RNA
• 2. rRNA part of the ribosome
• 2. tRNA transfers amino acids to ribosome for
  assembly.

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How Proteins are made

• Gene Expression
• Using the genetic information in DNA to make
  proteins.

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Gene Expression-2 steps

• 1. Transcription Copying a portion of DNA to
  form an mRNA (using RNA Nucleotides)
• 2. Translation 3 kinds of RNA work together to
  assemble ________ _________ into a protein
  molecule.

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GENE EXPRESSIONTranscription Translation
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• ..\Bio 1\DNA\DNA animation link.mht

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Transcription Practice

• Well make an mRNA from your paper DNA model.
• ---afterward, we will learn about the UNIVERSAL
  GENETIC CODE AND
• Then translation

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• Transcription page 290
• 1. enzymes unzip the DNA in the region of the
  gene to be transcribed.
• 2. Free nucleotides complimentary base pair with
  one strand of the DNA.
• The mRNA strand breaks away the DNA zips back
  up.
• mRNA leave nucleus, goes to cytoplasm.

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mRNA modification before leaving nucleus

• Introns
• non-coding regions of DNA removed from mRN
• (intervening regions that are not part of the
  protein recipe)
• Exons amino acid coding regions.
• the part whats left coding regions
  (expressed).
• NOW, the mRNA is ready to leave the nucleus

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Plan for Today

• Demonstrate proficiency in translation (step 2 of
  protein synthesis).
• Do this by completing activity following
  instruction.
• 15-20 minutes of Lorenzos oil. Watch for
  effects of treatment with monounsaturated fats.

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The Genetic Code-Secret codes for amino acids.

• Nearly Universal
• all organisms use the same code
• CODON each mRNA triplet

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The Central Dogma of Biology

• DNA mRNA Protein

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GENE EXPRESSION
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Protein Synthesis Part 2. Translation

• Translating the mRNA into a sequence of amino
  acids to form a protein.
• All three RNAs take part.

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ROLES OF RNAS IN TRANSLATION

• mRNA has the codon
• tRNA carries the amino acids translates the
  codon
• 20 different kinds of tRNA
• 20 different amino acids
• Has a nucleotide sequence complimentary to mRNA
  called an ANTICODON
• rRNA is part of the ribosome

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tRNA

• Each kind of tRNA carries only _____type of
  _________.
• Amino acid carried at one end.
• Three- base ANTICODON.
• This pairs up with an mRNA codon during
  translation.

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Now, theTRANSLATION STEPS

• 1. A ribosome attaches to an mRNA strand.
• 2. Amino acids brought to the ribosome by tRNA.
• The codon AUG codes for Methionine and
  signals the start to translation.
• The tRNA carrying Methionine attaches to the
  ribosome, translates with its Anticodon _____.

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• 3. The ribosome slides over the mRNA to the next
  codon.
• A new tRNA attached next on the mRNA, translates
  with its anticodon, releases its corresponding
  amino acid which bonds to Methionine.

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• Translation continues until a stop codon is
  reached.
• Complete protein detaches from ribosome.
• mRNA disassembles , so nucleotides can be reused.

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Translation PracticeDirections Underline the
codons beginning with the start codon. Identify
the corresponding anticodon and amino acid. Join
the amino acids into a chain.

• Amino acid
• anticodon
• mRNA G G U A U G C C U UC G G A G U U A A C A
  G C G UA A

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Translation PracticeDirections Underline the
codons beginning with the start codon. Identify
the corresponding anticodon and amino acid. Join
the amino acids into a chain.

• Amino acid-------Met Proline Serine Glut
  Phen Threo Alanine Stop
• Anticodon C C A U A C G G A A G C C U C A A
  U U G U C G C A U U
• mRNA G G U A U G C C U U C G G A G U U A
  A C A G C G U A A

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• tRNA
• On bottom end, is an anticodon - a 3- nucleotide
  sequence complimentary to mRNA.
• tRNA base pairs with an mRNA codon
• On top is the corresponding Amino Acid.

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Practice

• Chapter review Question 15

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Gene Expression 1. Transcription 2.
Translation
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Section 11.3 Genetic Changes

• Mutations change in ________ sequence
• Cuused by
• Errors in relpication
• Errors in transcription
• Errors in cell division
• External egents

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Mutations in reproductive cells

• Passed on to offspring if mutations occur in
  ________or __________cells
• Rarely have a positive effect
• Important in evolution-if it permits enhanced
  survival capability in its environment.

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Mutations in body cells

• Not passed on to _____________gt
• But may cause problems for the individual.
• Passed on in cell division.
• If genes controlling cell division are affected,
  may lead to _______.

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Point Mutations

• A change in a single ____ ____.
• May change the structure of a protein its
  function.
• THE DOG BIT THE CAT
• THE DOG BIT THE CAR

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Frameshift Mutation

• The addition or ________ of a single base .
• Each codon after this would be affectedshifted.
• It shifts the reading codons.
• More harmful than point mutations.
• WHY???

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Practice Problems

• Figure 11.1 answer question and prepare
  explanations.
• Problem Solving Lab 11.3
• p. 299.
• Problem Solving Lab 11.2 p. 300.

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• Figure 11.3

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End of Chapter 11

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