O T T F F S S E __

What comes next?

O T T F F S S E __

It’s EASY if you know the PATTERN!

(Just like Punnett Squares)

NE

WO

1 2 3 4 5 6 7 8

HREE

OUR

IVE

IX

EVEN

IGHT

9

NINE

CHAPTER 11-2: PROBABILITY &

PUNNETT SQUARES

Go to Section:

Tossing Coins

If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin

ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

Section 11-2

Interest Grabber

Go to Section:

Interest Grabber Answers

1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?

2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?

3. If you compiled the results for the whole class, what results would you expect?

4. How do the expected results differ from the observed results?

Results will vary, but should be close to 5 heads and 5 tails.

The results for 20 tosses may be closer to the predicted 10 heads and 10 tails.

The results for the entire class should be even closer to the number predicted by the rules of probability.

The observed results are usually slightly different from the expected results.

It can be written as a:Fraction ____

Percent ____

Ratio ____

1/425%

1:3

Probability is the likelihood that a particular event will occur.

EX: COIN FLIP

There are 2 possible outcomes:

or

http://www.arborsci.com/CoolStuff/CoinFlip.jpg

• The chance the coin will land on either one is:

____ ____ ____1/2 50% 1:1Alleles segregate randomly just like a coin flip. . . So we can use probability to predict outcomes of genetic crosses.

PROBABILITYPast outcomes do not affect

future ones.Probability works best predicting

a large number of events.The more flips…the closer results

will be to the expected 50:50 average.

If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too.

Dominant allele is represented by a capital letter.(usually the first letter of the trait)

Recessive allele is represented by the SAME lower case letter.

Ex: Tall = T Short = t

MENDEL’S PRINCIPLE OF DOMINANCE

When both alleles in the pair are the same, the organism is homozygous (purebred/truebred)EX: TT or tt

When both alleles in the pair are different, the organism is heterozygous (hybrid)Ex: Tt

HOMOZYGOUS VS. HETEROZYGOUS

Genotype: The genetic makeup of an organism

Phenotype: The expressed trait of an organism or its appearance.

PHENOTYPE VS. GENOTYPE

MONOHYBRID CROSS: CROSSING A ONE GENE TRAIT.

A Punnett square for a monohybrid cross looks like this:

Punnett squares are used to show possible offspring from a cross between 2 parents.

oParent alleles go at top and on left side

o Boxes show possible combinations

T T

T

t

1. Figure out what parent alleles are2. Choose correct Punnett square size3. Put in possible parent gametes

4. Fill in boxes with offspring combinations5. Determine probabilities of phenotypes & genotypes

STEPS FOR MAKING CROSSES

MONOHYBRID CROSS IN PEA PLANTS

Tall is dominant over short

TALL = ____ SHORT = ____

T

t

Let’s make a cross! PURE TALL pure shortX

PURE TALL PARENTWHAT ARE THE PARENT ALLELES?

T T _________

T T

HOMOZYGOUSdominant

What gametes can it make?

PURE SHORT PARENT WHAT ARE THE PARENT ALLELES?

t t _________

t t

Homozygous recessive

What gametes can it make?

GENOTYPE _____ PHENOTYPE _______

_____ of the offspring

____ % ___/4 will be tall

T T

t

t

T t T t

T t T t

Tt TALL

ALL

1004

LET’S TRY ANOTHER: HYBRID X HYBRID

HYBRID TALL PARENT WHAT ARE THE PARENT ALLELES?

T t _________

T t

HETEROZYGOUS

What gametes can it make?

GENOTYPES¼ = _____½ = _____¼ = _____

T t

T

t

T T T t

T t t t

PHENOTYPES ____ or ____% _________ ____ or ____% _________

TT

75

Tttt

3/41/4 SHORT

TALL25

PRACTICE MAKING GAMETES FOR A MONOHYBRID CROSS

Tall = ____ Round seeds = ___

Short = ____ Wrinkled seeds = ___

T

tR

r

WHAT ARE THE POSSIBLE GAMETES?

Homozygous Tall parent =

What gametes can it produce?

T T

T T

WHAT ARE THE POSSIBLE GAMETES?

PURE wrinkled parent =

What gametes can it produce?

rr

r r

WHAT ARE THE POSSIBLE GAMETES?

Heterozygous Round parent =

What gametes can it produce?

R r

R r

WHAT ARE THE POSSIBLE GAMETES?

Hybrid Tall parent =

What gametes can it produce?

Tt

T t

Thomas Hunt Morgan applied Mendel’s principals to fruit flies to see if he would get the same results in an animal.