Download Genetics and Probabilty

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
Flipping Coins
Heads vs. Tails
Probability of Getting Heads = 50% or ½
Probability of Getting Tails = 50% or ½
Corresponds to Sorting of Gametes
Tt = 50% chance of getting T and 50% chance of getting t
Calculating Receiving Gametes
 Rule of Multiplication: The probability of a result is the
product (multiply) of the individual probabilities.
Ex: Tt x Tt
The probability of getting TT

Probability of T = ½
Probability of T = ½
Total Probability = ½ x ½ = ¼

Probability of tt =
• ½x½=¼

Probability of Tt
• ½
• WHY? Two Possible Ways of getting Tt from Tt x Tt
• Tt or Tt
• Each has an individual probability of ¼ so added together = ½
T
T
t
t

Rule of Addition: If a result has multiple probabilities, the total
probability of that result is the sum (addition) of the individual
probabilities.

Cross: TT x tt
o Probability of Tt:

Cross: Tt x tt
o Probability of Tt
o Probability of tt
o Probability of TT
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Multiple Genes: Dihybrid and beyond
Find the individual probability of each gene pair and
multiply all together.
Cross: AaBb X AABb
o Probability of AaBB:
• Probability of Aa = ½
• Probability of BB = ¼
• Total Probability of AaBB= ½ x ¼ = 1/8

Cross AaBb x AaBb
o Probability of AaBb
• Probability of Aa = ½
• Probability of Bb = ½
• Probability of AaBb = ½ x ½ = ¼
-
Probability of AABB
-
Probability of Aabb

Cross AaBBCc x AABbCc
o Probability of AABBCC
o Probability of AaBbCc
o Probability of AAbbCC