Name: _____________________________Mrs. Begis Biology
Pd: _________
Probability and Punnett Squares
Mendel’s Results

Mendel repeated his experiments many times to see what would happen

He realized that for each cross, he got _______________________________________________
o
Ex) whenever he crossed __________ for height, ____________________________ and
___________________________________

Mendel realized that he could apply the principals of ________________________ to explain the
_________________________________
Genetics and Probability

Probability – __________________________________________________________________

Example – Coin Flip
o
The chances that a coin will land heads up is ___________________________________
o
The chances that a coin will land tails up is _____________________________________
o
If you flipped a coin and it came up heads, what are the chances that it will come up heads the
next time? ________________ The next time?_____________________

Each event is _______________________ of each other, so each time is a _____ chance
Coin Toss Activity

Hypothesis: If I toss a coin 2 times, I would expect to get _______ Heads and ________ Tails.

Toss your coin 2 times and record results
o
Toss 1 ______ H _______ T
o
Toss your coin 8 more times and record results
Toss 2 ______ H _______ T
Toss 3
Toss 7
Toss 4
Toss 8
Toss 5
Toss 9
Toss 6
Toss 10

Actual Coin Toss Results (class results)
o
For first 2 tosses:

o
Total Results

o
Number Heads ______ Number Tails ______
Number Heads ______ Number Tails ______
Did the actual results for the entire class come closer to your hypothesis of 50/50 chance for
heads and tails?

How is Coin Flipping Relevant to Genetics?

When we are dealing with probabilities of an event, ____________________________________
______________________________________________________________________________

Each event is ________________________________ and therefore has just as _______________
chances for an outcome as the one before

The segregation of alleles is _______________________________________, just like a coin toss
o
You randomly get what you get, every single time
Punnett Squares

Punnett Square – _______________________________________________________________
______________________________________________________________________________

Dominant traits are expressed by _______________ letters (_____)

Recessive traits are expressed by _______________letters (_____)

Homozygous – organisms that have ________________________________________ (TT or tt)
o

Are _______________ (pure-bred) organisms for a trait
Heterozygous – organisms that have ____________________________________________ (Tt)
o
Are _______________ organisms for a particular trait
Punnett Square Results

The outcomes of a punnett square can be described by both their “letters” and their “appearances”

Phenotype – _____________________________________________________ (the appearance)
o

Genotype – __________________________________________________________ (the letters)
o

Ex) ____________________________________________________________________
Ex) ____________________________________________________________________
Organisms can have the same phenotype even though they have different genotypes
o
________________________________________________________________________
Probability and Segregation

Was Mendel model for segregation correct when looking at alleles for height?
o

Are we able to determine the same results by looking at probabilities for height?
o

_______________ (______________________________example)
_______________ (______________________________example)
The results are the same no matter how you look at it
Probabilities Predict Averages

Probabilities can predict the ______________________________of a ____________________of events
(remb. the coin tossing)

They cannot predict the ______________________________of an ___________________ event
o

The predictions are based on chances for ______________________________________
When dealing with genetics, the _______________ the number of offspring, the _____________ your
results will be to the _______________________number