1. O T T F F S S E __
What comes next?

2. It’s EASY if you know the PATTERN! (Just like Punnett Squares)9
NINE
O T T F F S S E __ I V E X
EVEN
IGHT N E W O H R E O U R

3. PROBABILITY & PUNNETT SQUARES 11-2

4. PROBABILITY
____________________ is the __________ that a particular _________________
likelihood
event will occur
It can be written as a:
Fraction ____
Percent ____
Ratio ____
1/4
25%
1:3

5. COIN FLIP 1/2 50% 1:1 There are 2 possible outcomes: HEADS TAILS
COIN FLIP
There are 2 possible outcomes:
HEADS TAILS
The chance the coin will land on either one is:
____ ____ ____
Alleles segregate randomly just like a coin flip. . . So can use probability to predict outcomes of genetic crosses.
1/2
50%
1:1

6. PROBABILITIES _____ outcomes ______ affect _________ones
_____________works ______ in ___________ a ________ number of events.
PAST
DON’T
FUTURE
If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too.
Probability
predicting
best
large
The more flips. . . The closer results will be to
the expected 50:50 average.

7. DOMINANT/RECESSIVE T t capital Dominant Recessive lower-case
_____________ allele is represented by a ____________ letter. (usually the first letter of the trait)
____________ allele is represented by the SAME
_________________ letter.
EX: Tall = ______
Short =______
capital
Recessive
lower-case T t
NOT S for short

8. HOMOZYGOUS HETEROZYGOUS
When both alleles in the pair are the _______, the organism is _______________ or __________
EX: ____ or ___
When both alleles in the pair are _____________, the organism is
_________________ or _____________
Ex: ____
SAME
HOMOZYGOUS PURE
TT tt
DIFFERENT
HETEROZYGOUS HYBRID Tt

9. PHENOTYPE/GENOTYPE
The ________________ of an organism is its _____________
The ____________of an organism is
its _____________
genetic makeup
GENOTYPE
appearance
PHENOTYPE

10. MAKING A CROSS for only a __________ trait = ____________________
ONE GENE
MONOHYBRID CROSS
A Punnett square for a MONOHYBRID CROSS looks like this:

11. PUNNETT SQUARES
are used to show possible offspring from a cross between 2 parents
_______________ go at
top and on left side
Boxes show ____________ ___________________
Parent alleles
T T T t
possible offspring combinations

12. STEPS FOR MAKING CROSSES
Figure out parent alleles
Choose Punnett size
Put in parent gametes
Fill in offspring combinations
probabilities phenotypes genotypes
1. ___________ what _________________ are
2. ________correct__________ square __________
3. ______ possible_______________________
4. ______ boxes with _____________________
5. Determine ____________of_____________& ____________

13. T t TALL = ____ SHORT = ____ IN PEA PLANTS Tall is dominant over short
LET’S MAKE A CROSS!
PURE TALL PURE SHORT X

14. PURE TALL parent What are the parent alleles?
T T _________
HOMOZYGOUS  
What gametes
can it make? T T

15. PURE SHORT parent What are the parent alleles?
t t _________
HOMOZYGOUS  
What gametes
can it make? t t

16. T t T t T t T t T t ALL _____ of the offspring ____ % ___/4 will be
100 4
T t
T t Tt
TALL
GENOTYPE _____ PHENOTYPE _______

17. HYBRID TALL parent What are the parent alleles?
T t _________
HETEROZYGOUS  
What gametes
can it make? T t

18. T t T t T t T T T t t t GENOTYPES ¼ = _____ ½ = _____ TT Tt tt 3/4 75
TALL
PHENOTYPES ____ or ____% _________
____ or ____% _________
1/4 25
SHORT

19. PRACTICE MAKING GAMETES for a MONOHYBRID CROSS
Tall = ____ Round seeds = ___
Short = ____ Wrinkled seeds = ___ T t r

20. What are the possible gametes?
Homozygous Tall parent =
What gametes can it produce?
T T   T T

21. What are the possible gametes?
PURE wrinkled parent =
What gametes can it produce? rr   r r

22. What are the possible gametes?
Heterozygous Round parent =
What gametes can it produce?
R r   R r

23. What are the possible gametes?
Hybrid Tall parent =
What gametes can it produce? Tt   T t