Genetics and Heredity

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Genetics and Heredity
Passing on traits from parent to offspring is
heredity! What are some traits that you got from
your parents?
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Gregor MendelCirca. 1850s
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Mendels Success

• Pea plants grew quickly and were inexpensive
• Mendel realized that pea plants had different
  traits for example Tall vs. Short
• Mendel repeated his experiments many thousands
  of times and calculated data.

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• Be mendel and plant peas!

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Dominant Traits

• In pea plants Purple flowers were dominant. So a
  purple parent crossed with a white parent always
  resulted in 100 purple.
• WW x ww Ww.
• Dominant traits are symbolized by uppercase
  letters WW dominant purple.

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Recessive Traits

• Recessive traits are symbolized by little letters
  ww recessive (white).
• ? So if you had a plant with the genotype Ww
  what color would it be according to the law of
  dominance?
• Purple!

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Gene Segregation.what does segregation mean?

• Mendel thought that genes had two genes for each
  trait (one from mom one from dad)
• These genes were then symbolized by letters. WW
  dominant purple and ww recessive.
• These genes separate in the formation of gametes.
  (so your parent can only give you 1 gene)
• WW x ww Ww.

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Punnett Squares

• The punnett square is a visual aid to help in
  calculating ratios of genetic probability.
• Insert Alleles

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Terminology (the study of terms)

• Allele- each alternative form of a gene either W
  or w
• Genotype- the combination of genes Ww
• Phenotype-the appearance of that trait Purple
• Homozygous-two alleles are the same WW or ww
• Heterozygous- two alleles are different Ww

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The genotype codes for the phenotype
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What is the mothers Genotype? What is the first
childs genotype? What is the fathers
Phenotype? Which fish are homozygous and which
ones are heterozygous?
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Two Traits

• Boxhead

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Probability Calculation

• A coin has two sides what is the probability of
  flipping it and ending up tails?
• What is the probability of it being tails 3x in a
  row?
• A die has 6 sides what is the probability of a
  two being rolled?

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Incomplete Dominance
The four oclock exhibits incomplete
dominanceboth genes are expressed equally. RR
x RR the apostrophe is known as prime Say
R prime
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Sex Determination (the easiest cross ever!)

• Women have XX chromosomes and men have XY
  chromosomes.
• XX x XY