Honors Biology Ch. 12

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HonorsBiology Ch. 12

• Molecular Genetics

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CH. 11 Molecular Genetics

• I. DNA The Chemical Basis of Heredity
• - forms the universal genetic code of cells
• - contains instructions for making all of a
  cells proteins

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James Watson Francis Crick- discovered the
structure of DNA in 1953
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X-ray Diffraction of DNA
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A. DNA Structure

• 1. Components of DNA (3 Main Parts)
• a. Sugar
• (Deoxyribose)
• b. Phosphate
• c. Bases

Deoxyribonucleic Acid
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c. Bases

• 1) Adenine (A) Guanine (G)
• 2) Cytosine (C) Thymine (T)

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2. Nucleotide

• - a subunit of a nucleic acid containing a
  sugar, a phosphate, and a base

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3. DNA Shape

• - double helix
• a. backbone - sugars and phosphates
• b. paired bases form on the inside
• c. Base Pairing Rule A T , C G

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The Watson-Crick Model of DNA Structure
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B. Replication

• - process by which DNA makes an exact copy of
  itself

2 Exact Copies of DNA
Original DNA
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DNA Replication
Parental DNA double helix
FreeNucleotides
New double helix with 1 old 1 new strand
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II. From DNA to Protein

• A. Genes and Protein
• 1. Gene
• - a specific sequence of bases in DNA
  that determines the sequence of amino
  acids in a protein

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2. Proteins

• - very complex structure
• - 3 basic shapes helix, pleated sheet, globular
• - proteins contain between 50 - 2000 amino acids

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Illustration of Protein Structure
Primary(Amino Acid Sequence)
Tertiary(Bending)
Quaternary(Layering)
Secondary(Helix)
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Pleated Sheets
HydrogenBonds
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Structural Proteins
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HairStructure
Hair Cell
Single hair
Microfibril
Protofibril
disulfide bridges
SS
SS
Hydrogen bonds
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Curling of Hair
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B. RNA Structure

• - Nucleic acid that makes protein

Ribonucleic Acid
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B. RNA Structure

• DNA RNA
• Shape double helix single helix
• Sugar deoxyribose ribose
• Base thymine uracil
• Size very large smaller
• Location nucleus cytoplasm
• Function - stores genetic - makes
• info protein
• - replication
• - makes RNA

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C. Transcription

• - the copying of a genetic message from DNA to RNA

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C. Transcription

• - the copying of a genetic message from DNA to RNA

DNA base pairs separate
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C. Transcription

• - the copying of a genetic message from DNA to RNA

DNA half transcribes RNA
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C. Transcription

• - the copying of a genetic message from DNA to RNA

RNA released to make protein
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Transcription First Two Steps
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Transcription Last Step
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Information Flow
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RNA Transcription in Action
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Three Types of RNA
mRNA
codons
Largesubunit
Ribosomecontains rRNA
tRNA docking sites
Smallsubunit
Met
Amino acid
tRNA
anticodon
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D. Messenger RNA (mRNA)

• - carries the information for making a protein
  from DNA to the ribosomes
• - acts as a template (pattern)
• - contains codons
• triplets of bases that code for a
  particular amino acid

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- Start Codon

• (AUG) - marks the start of a polypeptide
• - Stop Codon
• (UAA, UAG, UGA) - marks the end

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E. Transfer RNA (tRNA)

• - carries amino acid to specific place on mRNA
• - contains Anticodon
• triplet of bases complimentary to mRNA codon

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F. Ribosomal RNA (rRNA)

• - transcribed in nucleus and combined with
  protein into ribosomes (site of protein synthesis)

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III. Translation

• - protein synthesis
• - decoding the "message" of mRNA into a protein

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Information Flow
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Translation Initiation
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Translation Elongation 1
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Translation Elongation 2
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Translation Elongation 3
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Translation Elongation 4
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Translation Elongation 5
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Translation Termination
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IV. Genetic Mutations
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IV. Genetic Mutations

• - any change in the nucleotide sequence of DNA
• - can occur in any cell
• Somatic Mutations
• - may be harmful but not inherited
• Gamete Mutations
• - can be inherited

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IV. Genetic Mutations

• - usually recessive
• - most are harmful
• - some harmless
• - few beneficial (leads to evolution)

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A. Causes

• - Mutagens
• - UV, X-rays, other radiation, chemicals
  (asbestos, etc.)

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B. Types of Mutations

• 1. Point Mutation
• - change of a single base
• - ex sickle-cell anemia

AUG GGG CUU CUU AAU
AUG GGG CAU CUU AAU
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Normal Red Blood Cells
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Sickled Cells
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2. Frameshift Mutation

• - addition or deletion of a single base

AUG GGG CUU CUU AAU
AUG GGG CAU UCU UAA U
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3. Chromosomal Mutation

• - change in an entire chromosome or in chromosome
  number within a cell

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a) Translocation

• - transfer of a chromosome segment to a
  nonhomologous chromosome

Normal
Translocation
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b) Inversion

• - rotation of a chromosome segment

Normal
Inversion
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c) Insertion

• - breaking off of a chromosome segment and
  attaching to its homologue

Normal
Insertion
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d) Deletion

• - chromosome segment left out

Normal
Deletion
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e) Nondisjunction

• - failure of homologous chromosomes to segregate
  during meiosis

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Human Chromosomes(23 homologous pairs)
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Down syndrome(Trisomy 21)
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Incidence of Down Syndrome
Number per 1000 Births
Age of Mother (years)
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Klinefelters syndrome(XXY)
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f) Polyploidy

• - having a multiple set(s) of chromosomes

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Speciation by Autopolyploidy in Plants
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The Evolution of Wheat
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A Tetraploid Mammal
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Turners Syndrome (Monosomy X)
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XYY Syndrome
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Trisomy X (XXX)
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Klinefelters Syndrome (XXY)
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Down Syndrome (Trisomy 21)
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Normal Female
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Edwards Syndrome (Trisomy 18)
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Cri du Chat (deletion in chromosome 5)
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The End

• of Ch. 11

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Overview ofInformation Flow
(Cytoplasm)
DNA
(Nucleus)
Transcription
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rRNA
tRNA
mRNA
Proteins
tRNA
Ribosomes
mRNA
tRNA-AA
Translation
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InactiveProtein
Modification
ActiveProtein
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AminoAcids
Degradation
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Substrate
Product
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Complementary Base Pairing
gene
(a) complementaryDNA strand
templateDNA strand
codons
(b) mRNA
anticodons
(c) tRNA
amino acids
(d) protein
Methionine
Glycine
Valine