probability & genetics
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Probability & Genetics
Genetics & Probability
Mendel’s laws:segregation independent assortment
reflect same laws of probability that apply to tossing coins or rolling dice
Probability & genetics
Calculating probability of making a specific gamete is just like calculating the probability in flipping a coinprobability of tossing heads? probability making a B
gamete?50%
100%BBB
B
BbB
b
Probability & genetics
Outcome of 1 toss has no impact on the outcome of the next tossprobability of tossing heads each
time?probability making a B gamete each
time?
50%
50%Bb
B
b
Calculating probabilitysperm egg
1/2 1/2
offspring
=x 1/4P P PP
P p Pp
1/2 1/2 =x 1/4p p pp
p P
Pp x Pp
P pmale / sperm
P
pfemal
e / e
ggs
PP Pp
Pp pp
1/2 1/2 =x 1/4
1/2 1/2 =x 1/41/2
+
Chance that 2 or more independent events will occur togetherprobability that 2 coins tossed at the
same time will land heads up
probability of Pp x Pp pp
Rule of multiplication
1/2 x 1/2 = 1/4
1/2 x 1/2 = 1/4Pp
P
p
Calculating probability in crossesUse rule of multiplication to predict crosses
YyRr YyRrx
yyrr
?%
Yy Yyx Rr Rrx
1/4 1/4
1/16yy rr
x
Apply the Rule of Multiplication
Got it?Try this!
AABbccDdEEFf AaBbccDdeeFfx
AabbccDdEeFF
Bb x Bb bbcc x cc ccDd x Dd DdEE x ee EeFf x Ff FF
AA x Aa Aa 1/21/4
11/2
11/4 1/64
Rule of addition Chance that an event can occur
2 or more different ways sum of the separate probabilitiesprobability of Bb x Bb Bb
sperm egg offspring
1/2 1/2 =x 1/4B b Bb
1/2 1/2 =x 1/4b B Bb
1/41/4+
1/2
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