Punnett Squares

Tuesday - Bellwork Create a Venn diagram comparing phenotype and genotype: Use the words physical appearance, genetic makeup, heterozygous, homozygous, describes an organism, purple, tall, Pp, green,pp Describe the difference between complete dominance, incomplete dominance, and codominance IFC: What is the first step in the scientific method? A. make a hypothesis B. Ask a question C. draw conclusions D. do background research

Wednesday bellwork – 10/23 IFC: Chemists often make models of molecules using balls to show atoms and sticks to show bonds. The models help them see what the molecules might look like. What is a limitation of this model? The models wont last as long as real molecules The colors of the balls and sticks would not show the molecule’s real color Real molecules are very small and complex, models could only approximate what they look like. Chemists are bad model makers so they would not be very useful In a cross between a yellow fish and a blue fish all of the offspring are green. What kind of dominance is this? In some flowers blue and white are codominant. Describe the phenotypes of each of these flowers BB WW BW

Science Fair Topic and Question research Today you will find a testable question for your science project. Log in to my website: akbrownscience.weebly.com Choose the science fair tab. You will find links to sites with topic and question ideas. Look through the topic ideas and questions to help you get an idea for your project – choose at least 3 today and write them in your science fair log Remember to write down the site you got the ideas from so you can find them again When you finish, begin looking for background research on your project.

Thurs. Bellwork – 10/24 IFC In Pea plants, round peas (R) are dominant over wrinkled peas (r). What is the genotype of a homozygous recessive pea plant? What is its phenotype? What is the genotype of a heterozygous pea plant

EQ: how are patterns of inheritance studied? OBJ: I can predict patterns in heredity because I can create Punnett squares and read pedigrees SC.7.L.16.2 Determine the probabilities for genotype and phenotype combinations using Punnett Squares and pedigrees. 6

What is probability? Probability is the likelihood that a particular event will occur It can be written as a: Fraction ____ Percent ____ Ratio ____ 1/4 25% 1:3

What is a Punnet Square? A Punnett square is a model that helps you find the probability of different outcomes from genetic crosses

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

Probability and Tossing Coins If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 6 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin 6 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 6 tosses.

Assuming that you expect 3 heads and 3 tails in 6 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? Add your results to those of your partner to produce a total of 12 tosses. Assuming that you expect 6 heads and 6 tails in 12 tosses, how close are these results to what was expected? If you compiled the results for the whole class, what results would you expect? How do the expected results differ from the observed results?

What is a Punnett Square A Punnett square helps us predict the probability that an offspring with a particular genotype and phenotype will be produced I wish I could make a punnett square

How do I create a Punnett Square? To Make a Punnett square there are a few simple steps to follow:   1) draw a box and divide it into four parts

How do I create a Punett Square? 2) label the left hand side of the box with the genotype of one parent (R=Red, r=White) R r

How do I create a Punnett Square 3) label the top of the box with the genotype of the other parent R r

How do I create a Punnett Square 4) In the middle boxes place 2 letters. One letter comes from the left side and one from the top R r Rr Rr rr rr

How do I Interpreti a Punnett Square You now know the possible genotypes for the offspring of these two parents . The genotypes and phenotypes can be given a ratios, fractions, or %s

Practice Problems Complete and check with your shoulder partner . A cross between a female with straight hair (HH) and a male with curly hair (hh)   genotypes___________ phenotypes__________()

Black eyes (B) are dominant over red eyes (b) in some rats. B b B b Black eyes (B) are dominant over red eyes (b) in some rats. Make a cross between two HETEROZYGOUS rats. BB Bb Bb bb 25% BB 50% Bb 25% bb What are the possible genotypes of the offspring? What are the possible phenotypes of their offspring? (% and color) 75 % black eyes 25% red eyes

B B b Make a cross between a Homozygous Dominant rat and a homozygous recessive rat. Bb Bb Bb Bb 100% eterozygous What are the possible genotypes of the offspring? What are the possible phenotypes of their offspring? (% and color) 100% Black eyes

Practice Problems 2. A cross between a black dog (Bb) and a brown dog (bb)   genotypes_____________ (#BB:#Bb:#bb) phenotypes____________ (#Black:#Brown)

Practice Problems 3. A cross between a yellow corn (Yy) and another yellow corn (Yy) (y = white corn)   genotypes_________________ phenotypes_______________

Guinea Pig Punnet squares Write the possible outcomes for the guinea pig offspring in the boxes Cut out the appropriate guinea pig and glue in the space

Bellwork: IFC While scientists already know a great deal about DNA, they continue to learn more about its role in genetics.What is the basis of scientists’ current understanding of DNA? A. They guess how they think it works. B. They use combined empirical evidence from many scientists. C. They only use evidence that they have personally proven. D. They assume they already know all there is to know, even when evidence contradicts that assumption. 3. Create a Punnett square to show a cross between a yellow corn (Yy) and another yellow corn (Yy) (y = white corn) genotypes_________________ phenotypes_______________

Celebrity punnett squares You will pick 2 random celebrities Their traits are listed on their picture – do not destroy them I need them all day Make 6 punnett squares to determine the genotypes and phenotypes of their offspring