Gene Expression How do genotypes become phenotypes?

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Gene ExpressionHow do genotypes become
phenotypes?
23 from dad
23 from mom
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• Chromosome
• Structure found in the nucleus of all cells
• Made of DNA coiled around histone proteins,
  compacted
• DNA
• Double helix shape
• Stores genetic gene information
• Self-replicates to produce 2 exact copies of
  itself
• Gene
• A segment of DNA that serves as a code for a
  specific phenotype

Gene for Type A Blood
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Genotype
Phenotype
inherit
Propose how this occurs. What other factors might
be included within the blue arrow? How do you
go from alleles (A, a) to an actual phenotype
that is noticeable?
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DeoxyriboNucleic Acid

• Antiparallel strands (gene is 5? 3)
• Monomers nucleotides
• Adenine, Thymine, Cytosine, Guanine
• 1 nucleotide 3 parts
• Deoxyribose sugar
• Phosphate
• Base
• Uses complimentary base pairing rules A ?? T
  and C ?? G

5 CGTGGTTAAATCT 3
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The Central Dogma of Biology

• DNA RNA Protein

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The Central Dogma
Replication
Translation
Transcription

• DNA RNA
  Protein

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DNA Replication

• DNA is copied accurately to preserve an
  organisms genotype
• Occurs before cell division so each chromosome
  has 2 copies to give
• meiosis (cell division for gametes)
• mitosis (cell division for growth)
• Takes place in the nucleus
• Enzymes used in process
• Helicase - Unwinds double helix
• DNA Polymerase - Creates new strand

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DNA Replication
New DNA strands are formed based off original DNA
sequence
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DNA Replication
Gene 5 ? 3
GAGTCCTGTCATAAAATG 3

• 5 CGTGGTTAAATCT
• 3 GCACCAATTTAGA

Template Strand 3 ? 5
CTCAGGACAGTATTTTAC 5
Lets model DNA Replication!
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Whats next?

• After DNA Replication, there is enough DNA make 2
  new cells and then again, and again until the
  organism stops performing cell division (i.e.,
  never, really). Once a new cell is made, it can
  begin to use the DNA to create phenotypes.We
  call this next part Gene Expression, or the
  production of a phenotype given information from
  the genotype (gene segments of DNA) and it
  can be divided into 2 steps Transcription and
  Translation.

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Transcription

• Produces a RiboNucleic Acid (single) strand using
  a DNA template
• DNA is read from 3 ? 5 (template strand)
• Transcription enzyme RNA Polymerase
• Takes place in the nucleus
• In gene expression, mRNA is made
• Base pair rules

C ? G G ? C T ? A A ? U
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Lets Transcribe!

• Gene 5 TCATGCAGAGGAGATTAA 3
• Template 3 AGTACGTCTCCTCTAATT 5
• mRNA 5 3
• Gene 5 GATCAGGGAGACTTAGCA 3
• Template 3 CTAGTCCCTCTGAATCGT 5
• mRNA 5 3

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Translation

• Produces an amino acid sequence using mRNA as a
  template
• mRNA is read from 5 ? 3 in triplets
  (codons)
• Codons code for amino acids
• Start codon is AUG but stop codon varies
• Enzyme that does this is called tRNA
• Takes place in cytoplasm at a ribosome
• After folding of polypeptide, a protein is formed!

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The Genetic Code
Examples AUG is Met (start) ACC is Thr AGA is
Arg! UAA is Stop UAG is Stop UGA is Stop
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• Use the Genetic Code to figure out what amino
  acids are assembled based on mRNA strand

Alanine
Threonine
Glutamate
Leucine
Arginine
Serine
Stop!
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Translation

• Gene 5 GATCATGCGTCTCCTCTAATT 3
• Template
• mRNA
• Amino Acids

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Translation

• Gene 5 3Template 3 CTCATACGGACAGTATTTTA
  C 5
• mRNA
• Amino Acids

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Once the amino acid sequence is complete, it
folds into a 3D glob a protein! Proteins do
all of our cellular work, so they create
phenotypes.
Discuss with a neighbor How do you get from
genotype to phenotype?
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Your Task

• Gene Expression Practice Worksheet
• Compare to key when finished to see if you have
  the skills!
• Homework due Friday
• Snorks

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Discuss with your neighbors

1. Where does DNA Replication take place?
2. Where does Transcription take place?
3. What does Transcription produce?
4. Where does Translation take place?
5. What does Translation produce?
6. The Genetic Code is used to figure out what amino
   acids are assembled based on the strand
   created from the strand

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What is the deal with 5 and 3?