Goal 3

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Goal 3

• DNA, Protein Synthesis, Genetics, Biotechnology
  and Evolution

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3.01 DNA, RNA and Protein Synthesis

• DNA is the code of life. It contains the
  information on how to make proteins.

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Structure of DNA

• DNA (deoxyribonucleic acid)forms a double-helix
  shape
• Consists of a sugar (deoxyribose), a phosphate,
  and a nitrogenous base
• Bases
• Adenine-Thymine
• Guanine-Cytosine
• (complementary base pairing)

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Nucleotide building blocks of DNA

• A nucleotide is made up of a phosphate group,
  nitrogen base (A,T,G,C) and sugar.

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Hydrogen Bonds

• Weak hydrogen bonds attach the two strands of the
  DNA molecule.

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DNA replication

• Copying of genetic material before mitosis and
  meiosis
• 3 steps
• 1) DNA unzips at hydrogen bonds
• 2) free nitrogenous bases join up to newly
  opened bases
• 3) sugar-phosphate backbone rebuilt

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The Code

• Every three nitrogen bases is the code for one
  amino acid.
• An error in a nitrogen base is called a mutation.

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RNA

• Ribonucleic Acid
• Single strand.
• Uracil instead of thymine.
• Ribose instead of deoxyribose.

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Types of RNA

• Messenger RNA carries DNA code from nucleus to
  ribosome
• (why cant DNA leave the nucleus?)
• Transfer RNA - carries amino acids from the
  cytoplasm to the ribosome
• Ribosomal RNA what the ribosome is made of

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Protein Synthesis

• Two Steps
• Transcription copying DNA code onto the mRNA
• Translation making protein in the ribosome

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Protein Synthesis

• Transcription
• DNA unwinds and unzips
• mRNA nucleotides match up to the complimentary
  DNA nucleotide
• Single strand of mRNA is made with the DNA code

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Protein Synthesis

• mRNA leaves the nucleus and carries the code to
  the ribosome

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Protein Synthesis

• Translation
• mRNA lines up in the ribosome
• mRNA triplet codes (codons)match up with tRNA
  triplet codes (anticodons)

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Protein Synthesis

• Translation continued
• Amino acids are put in correct sequence.
• Peptide bond forms between amino acids.
• Polypeptide folds into protein.

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Protein
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Reading and interpreting an mRNA codon chart

• Find each codon (3 base sequence) from the mRNA
• Use chart to find the correct amino acid that it
  codes for

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Gene Regulation

• All cells of an organism have the same DNA.
• What type of cell develops depends on which genes
  get turned on or off.
• This is why a multicellular organism is able to
  differentiate into many types of cells. For
  example skin cells, muscle cells, bone cells.

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Gene Regulation

• Cells respond to their environment by producing
  different types and amount of protein.
• Examples
• 1. You get cut and your skin cells need to make
  proteins to repair your skin.
• 2. Cancer may result when your cells make too
  many cells (protein).
• 3. Diabetes may result if your pancreatic cells
  dont make enough insulin (protein).

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3.02 Cell Division

• 2 Types of cell division
• Mitosis involved in growth, repair and asexual
  reproduction
• Meiosis involved in the production of gametes

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Examples of asexual reproduction

• Binary fission

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Asexual reproduction

• Budding in
• Hydra.

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Asexual Reproduction

• Cutting of a plant

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Mitosis

• Occurs in all body cells
• Results in 2 new genetically identical daughter
  cells
• Maintains the chromosome number
• Chromosomes DOUBLE ? then SPLIT
• Example humans 46 ?92 ?46

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Stages of Mitosis

1. DNA (chromosomes) replicate
2. Spindle forms, nuclear membrane disappears
3. Chromosomes line up along the equator
4. Spindle fibers shorten, bringing chromosomes
   towards poles
5. Cytoplasm divides

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Replicated chromosme

• Replicated chromosome is actually two identical
  chromosomes attached at the centromere

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Meiosis

• Occurs only in the sex organs (testes and
  ovaries)
• Results in 4 gametes (sex cells)
• Reduces the chromosome number in half (for sexual
  reproduction)
• Chromosomes
• DOUBLE ?SPLIT?SPLIT
• Example human 46?92?46?23

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Stages of Meiosis

1. DNA replicates
2. Chromosomes line up along the equator
3. Replicated pairs split
4. Chromosomes line up again
5. Centromere splits

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Sources of variation

• Crossing over (only occurs during meiosis).

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Sources of Variation

• Random
• Assortment
• Of
• chromosomes

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Sources of Variation

• Gene mutation
• Nondisjunction ?
• Fertilization

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3.03 Patterns of Inheritance

• Gregor Mendel
• Father of genetics
• Austrian Monk
• First noticed inheritance of traits
• Studied heredity in pea plants, and noted
  statistics included within monohybrid/dihybrid
  crosses

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Mendels Experiments

• Results of Mendels crosses with pea plants.
• He studied seven different traits.

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Genetic Vocabulary

• Dominant- allele which masks the phenotype of
  other alleles
• Recessive allele that will not be expressed if
  dominant allele is present

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Genetic Vocabulary

• Heterozygous (hybrid) the genes in the
  gene pair are different
• Homozygous (pure) the genes are the same

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Genetic Vocabulary

• Geneotype The actual genes of an organism
• Phenotype What an organism actually looks like.

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Genetic Vocabulary

• Parental generation
• F1 Generation
• F2 Generation

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Law of Segregation

• During meiosis, the gene pair splits and each
  gamete only has one member of each pair of
  genes.

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Law of Independent Assortment

• During meiosis, the genes in each gene pair move
  into the gametes independently of each other.
  Notice you can still get a 31 ratio between
  yellow and green or round and smooth.

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Genotype and Phenotype
A change in the environment also can affect the
phenotype. Although we often think of flamingos
as being pink, pinkness is not encoded into their
genotype. The food they eat makes their phenotype
white or pink
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Test Cross

• Mate unknown with a pure recessive.
• B black guinea pig
• b white guinea pig
• Black guinea pig BB or Bb?
• BB x bb Bb x bb
• Result only black Result black
• offspring and white pigs

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Incomplete Dominance
Blending of two traits.
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Incomplete Punnett Square
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Co-dominance

• Co-dominant alleles result in the expression of
  both traits. Examples roan shorthorn cattle of
  AB blood

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Pedigrees

• Tools used by scientists to trace inherited genes
  through a family tree
• Squares male
• Circlefemale
• Filledaffected
• Half filled carrier
• Emptynot affected

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Polygenic Traits

• Traits which are coded for by more than one
  allele.
• Usually results in a blending of traits (ex eye
  color, skin color, hair color)

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Polygenic Skin color
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Human Genetics

• Examples of single gene, autosomal inheritance
  patterns
• Sickle Cell Anemia
• Cystic Fibrosis
• Huntingtons Disease

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Sickle Cell Anemia

• Recessive
• Predominantly in people of African/African-
  American descent.
• Hybrid individuals are resistant to malaria
• Symptoms tired, pain in joints

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Cystic Fibrosis

• Recessive
• Predominantly in caucasians
• Symptoms mucous clogs lungs and other organs,
  individuals usually dont live past 20 years old

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Huntingtons Disease

• Dominant
• Symptoms Abnormal body movements,
• gradual deterioration or loss of intellectual
  abilities (dementia),
• behavior problems

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Blood Types
A and B are co-dominant. O is recessive.
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Punnett Square - Blood
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Sex Linked Traits

• Trait is more likely to be inherited by males
• Gene for these traits are found on the X
  chromosome, but not the Y because it is so short
• Recessive

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Sex Linked Traits

• Hemophilia
• Defective gene prevents the normal formation of
  the proteins for clotting (platelets)
• Symptoms uncontrollable bleeding when cut

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Sex Linked Traits

• Colorblindness
• Unable to distinguish between certain colors.
  For example red/green color blindness

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Karyotypes

• What sex is this individual?

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Karyotypes

• What disease does this individual have?

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3.04 Biotechnology
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Human Genome Project

• Scientists have uncovered the entire human DNA
  code.
• Information useful in screening for diseases,
  gene therapy and developing drugs.

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Gene Therapy

• Inserting corrected gene into person who has a
  defective gene.
• Still in the experimental stages.

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Gel electrophoresis
DNA fragments separate according to size
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Gel Electrophoresis

• Also called DNA fingerprinting. Used in crime
  scene investigations.
• Used to determine how closely related organisms
  are.

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Transgenic Organisms

• Having DNA from another species
• Example a cow or pig has a human gene
• Used to make human insulin by inserting human
  gene in bacteria

Firefly DNA inserted into tobacco plant
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Transgenic Cow

• A Dutch biotechnology company called Pharming has
  genetically engineered cows, outfitting females
  with a human gene that causes them to express
  high levels of the protein human lactoferrin in
  their milk

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Transgenic Bacteria
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Biotechnology

• Ethical issues and implications
• Stem Cell Research

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More controversy

• Genetically modified food (sometimes called
  Franken Food)
• Will it harm us?
• Will it harm the environment?
• Is it the future?

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3.05 Evolution

• Abiogenesis
• Life can come from non life
• Examples flies from meat
• Mice from rags
• Frogs and insects from mud

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Biogenesis

• Francesco Redi used flies, meat and screens to
  disprove abiogenesis.

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Biogenesis

• Louis Pasteur used specially made flasks and
  broth to prove biogenesis

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Theory of Natural Selection

• Charles Darwin
• Naturalist on the British Ship the HMS Beagle

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The Voyage
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Galapagos
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Iguanas and Tortoises
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Finches and Boobies
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Early earth

• Hypothesis that the first organisms to evolve
  were
• ANAEROBIC
• HETEROTROPHIC
• PROKARYOTIC

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Early Earth - Experiments

• Experiment
• Sparks (lightning)
• Gasses (volcanoes)
• Water droplets (rain)
• Heat (geothermal)
• NO OXYGEN
• 1 week amino acids

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Evolution of eukaryotic cells
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Evolution of aerobic and photosynthetic organisms

1. Prokaryotic anaerobic heterotrophic organisms
2. Prokaryotic autotrophs ? started to produce
   oxygen and change the ancient atmosphere
3. Eventually enough oxygen was present in the
   atmosphere to promote the evolution of aerobic
   organisms

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Evidence for Evolution

• Fossils
• Biochemical
• similarities
• Shared
• anatomical
• structures

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Patterns in the fossil record

• What can they tell us?
• The most primitive organisms are the oldest.
• The most advanced organisms are the youngest.

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Fossilization

• Relative Dating
• Finding the age by comparing the fossil to the
  rocks or fossils near by.

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Fossilization

• Absolute Dating
• Using radioactive isotopes to determine
  age.

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Biochemical similarities
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Similar Structures

• Similar
• embryological
• development can
• show close
• evolutionary
• relationships.

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Similar Structures

• Four different mammal limbs have the same
  basic bone structure.

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Mechanisms of Evolution
Variation (provides material) Geographic
Isolation Environment (selection pressures)
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Peppered Moth

• Variation provides material for natural selection.

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Geographic Isolation

• Examples Kaibab squirrel (top) and the Albert
  squirrel (bottom) from the Grand Canyon
• Galapagos finches
• Australias marsupials

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Natural SelectionRecent Examples
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Resistance to Pesticides
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