PROBABILITY PUNNETT SQUARES 11 2 Interest Grabber Section

PROBABILITY & PUNNETT SQUARES 11 -2

Interest Grabber Section 11 -2 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. 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. Results will vary, but should be close to 5 heads and 5 tails. 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? The results for 20 tosses may be closer to the predicted 10 heads and 10 tails. 3. 4. 4. If you compiled the results for the whole class, what results would you expect The results for the entire class should be even closer to the number predicted by the rules of probability. How do the expected results differ from the observed results? The observed results are usually slightly different from the expected results.

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

http: //www. arborsci. com/Cool. Stuff/Coin. Flip. jpg COIN FLIP There are 2 possible capital outcomes: HEADS TAILS The chance the coin will land on either one is: 1/2 ____ 50% ____ 1: 1 ____ Alleles segregate randomly just like a coin flip. . . So can use probability to predict outcomes of genetic crosses.

PROBABILITIES PAST DON’Taffect _____ones _____ outcomes ______ FUTURE If last coin flip was heads… there is still a 50/50 chance the next flip will be heads too. _______works ______ Probability predicting best in ______ a ____ number of events. large The more flips. . . The closer results will be to the expected 50: 50 average.

DOMINANT/RECESSIVE 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. T EX: Tall = ______ Short t =______ NOT S for short

HOMOZYGOUS HETEROZYGOUS When both alleles in the pair are the _______, SAME the organism is ________ HOMOZYGOUS or _____ PURE TT tt EX: ____ or ___ When both alleles in the pair are _______, DIFFERENT the organism is HETEROZYGOUS or _______ HYBRID _________ Ex: ____ Tt

PHENOTYPE/GENOTYPE genetic makeup The ________ of an organism is its. GENOTYPE _______ appearance The ______of an organism is PHENOTYPE its _______

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

PUNNETT SQUARES are used to show possible offspring from a cross between 2 parents Parent alleles go at ________ top and on left side Boxes show T possible ______ offspring combinations t __________ T T

STEPS FOR MAKING CROSSES Figure out what _________ parent alleles 1. ______ are Choose Punnett square _____ size 2. ____correct_____ Put in possible____________ parent gametes 3. ______ Fill in boxes with ___________ offspring combinations 4. ______ probabilities phenotypes 5. Determine ______of_______& genotypes ______

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

PURE TALL parent What are the parent alleles? TT T HOMOZYGOUS _____ T What gametes can it make?

PURE SHORT parent What are the parent alleles? tt t HOMOZYGOUS _____ t What gametes can it make?

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

HYBRID TALL parent What are the parent alleles? Tt T _____ HETEROZYGOUS t What gametes can it make?

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

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

What are the possible gametes? Homozygous Tall parent = What gametes can it produce? T TT T

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

What are the possible gametes? Heterozygous Round parent = What gametes can it produce? R Rr r

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