GENETICS

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GENETICS
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GREGOR MENDEL (1822- 1884)
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Self Fertilization Offspring Purebred
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Cross Fertilization Offspring Hybrid
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CROSS POLLINATION
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HYBRID
COCKER SPANIEL POODLE
COCKAPOO
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HYBRID
PUG BEAGLE
PUGGLE
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HYBRID
DOG AND WOLF
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Liger
male lion and a female tiger
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Peas!
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GENETIC TERMINOLOGY

• Genotype
• Phenotype
• Trait
• Allele

• Dominant
• Recessive
• Homozygous
• Heterozygous

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Dominant and Recessive Alleles

• Dominant allele- trait is always expressed if
  present
• - Written as capital letter
• - Ex. Tall T
• Recessive allele- only expressed if no dominant
  allele is present
• (Dominant allele masks this one)
• - For a particular trait written as the
  same letter but lower case
• - Ex. Short t

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• Genotype- the genes you get from your parents
• Two letters represent the two alleles
• One from mom one from dad
• TT, Tt, tt
• Phenotype- the physical trait, what you look like
  
• Tall short, yellow or green
• TT, tt what is the phenotype??

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• Homozygous - the same alleles for a gene
• TT, tt
• Heterozygous - having different alleles for a
  gene
• Tt

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Trait Height
TALL
SHORT
? alleles ?
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Gene- unit of inherited information in DNA
Allele- alternative form of a gene ( white
purple)
Flower Color Trait
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Test Cross- mate an unknown genotype ( TT or Tt)
with homozygous recessive (tt)
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Reginald Punnett
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In Starfish being red is dominant over being
pink. What would Patricks phenotype be? What
would his genotype be?
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Because Patrick is pink his phenotype is
PINK And since pink is recessive his genotype
would be rr
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Red is dominant over pink Suppose we had a
HETEROZYGOUS red starfish what would the genotype
be?
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Rr
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Lets do some MONOHYBRID CROSSES!Monohybrid
means we are only using ONE TRAIT
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STEP by STEP

• Select a good letter to use
• Write down your givens
• Determine parents and record
• Set up Punnett Square
• Determine genotypes phenotypes of offspring
• (use percentages or fractions)

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In pea plants being Tall is dominant over being
shortCross a Heterozygous Tall plant with a
Homozygous Tall plant
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Aa x AA
Geno 50 AA 50 Aa Pheno 100 Tall
A
A
A
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In sponges, being blue is dominant over being
yellow. Cross a heterozygous blue sponge with a
yellow one.
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Heterozygous Blue Bb Recessive Yellow bb so
we cross Bb x bb
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Time for some LOONEY Monohybrid Crosses on your
own!
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Red is dominant over Blue
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T EST C R O S S
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MENDELS LAWS

1. Dominance Recessiveness
2. Segregation
3. Independent Assortment

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PEDIGREE
male
female