Genetics and Probability

1. Genetics and Probability Go through the following slides and complete tasks on how to use punnett squares to predict genetic outcomes of offspring. Read each slide carefully and complete tasks.

2. Probability can be used to predict the results of genetic crosses. In other words you can figure out what fraction or percentage of the offspring will have the trait. To help figure this out punnett squares are used. A punnett square is a special chart that is used to show the possible gene combinations in a cross between two organisms. Before you can create punnett squares you must understand some of the key terms. Click on the button below to go to the next slide and view the definitions. Click on sound icon

3. The hybrid is circled because it has an Upper and lower case letter or not the same throughout. TT Tt tt The purebreds are circled because they have the same letters. TT Tt tt Hybrid Two different genes make up the trait. Click on the colored word hybrid for the example to appear. Purebred The genes are the same for the trait. Click on the blue word purebred for the example to appear.

4. This is the actual gene makeup of the organism. Click on the purple word genotype for an example. Click on the sound icon under genotype for an explanation The letters that makeup the trait. The following are examples. If red roses are dominant over white then the following could be possible genotypes. T = Red Rose t = White Rose The possible genotypes are circled TTTttt The rose could be red or white, so the phenotype will be red or white. If the genotype is TT or Tt the rose will be red. If the genotype is tt the rose will be white. Genotype Phenotype What the physical appearance of the trait or organism looks like. Click on the orange word phenotype to view the example. Click on the sound icon under phenotype for an explanation.

5. Phenotype Write the correct phenotype for the following examples Click on the gray box and type in what color fur each hamster has if black fur is dominant over white fur. B – Black fur b – White fur bb - BB - Bb - White Fur Black Fur Black Fur Once you have typed in your answers click on the answer button below and they will appear.

6. Genotype Write the correct genotype for the following examples Click on the gray box and type in what the gene makeup would be for each hamster. Black fur is dominant over white fur. B – Black fur b – White fur Once you have typed in your answers click on the answer button below and they will appear. Purebred Black Fur - White Fur - Hybrid Black Fur - BB bb Bb

7. Same upper case and lower case A a Different upper case and lower case S s Now that you understand the terms we will come back to the punnett squares. The first part of creating a punnett square is choosing the letter that will represent the genes. The only rule I have is that the letters you choose have a different upper and lower case. Click on both the good and bad example below. Bad Example Good Example

8. Kk Hh Gg Dd Ll Bb Cc Rr Oo Vv Click on the boxes below that would be good letters to choose to represent the genes that will be used for the punnett square. If not sure go back to the previous slide and look at the good and bad examples. If you have the following boxes checked then you are ready to move on. Gg Ll Hh Dd Bb Rr Once you have typed in your answers click on the answer button below and they will appear.

9. Now that you know how to pick the letter the next part is to figure out which is dominant and which is recessive. Remember dominant is the gene that hides the weaker trait whenever it is present. The dominant trait is always the capital letter. The recessive trait is always the lower case letter. Now click the word example. After you read through the example click on the sound icon, near the bottom, to listen to an explanation. Example In pea plants, round seeds are dominant over wrinkled seeds. Pick a letter to represent dominant and recessive genes. T = Round Seeds t = Wrinkled Seeds I chose the letter T to represent the dominant and recessive genes. Round is dominant so it is the capital T. The lower case t is wrinkled because it is recessive.

10. Try these out. Orange tulips are dominant over white tulips. Pick a letter to represent dominant and recessive. Write the letter and what it stands for in the gray box below. Click on answer to see if you are correct. Letters may be different, but make sure capital and lower case are different. B = Orange Tulips b = White Tulips Brown eyes are dominant over blue eyes in huskies. Pick a letter to represent dominant and recessive. Write the letter and what it stands for in the gray box below. Click on answer to see if you are correct Letters may be different, but make sure capital and lower case are different. H = Brown eyes h = Blue eyes

11. The second part to creating a punnett square is figuring out the genotypes of the parents. To do this you have to pay close attention to what the question is asking you to cross. Below is an example of a question. I underlined the key words that can help you determine the parents genotype. Click on the sound icon for explanation. In pea plants, round seeds are dominant over wrinkled seeds. Predict the genotypes and phenotypes of a cross between two hybrid round-seeded pea plants. Since they are both hybrid round that means their letters are different. The first thing you do is pick your letters, like on previous slide, and then you show the cross. The cross is shown by the X. R = round r = wrinkled Rr X Rr Parent 2 Parent 1 Hybrid round Hybrid round

12. B = Black Fur b = White Fur BB X bb Purebred Black fur Purebred White fur B = Brown eyes b = Blue eyes Bb X bb Hybrid brown eyed Blue eyes Try these!! Write the dominant/recessive letter and then the cross between the parents in the gray box under the question. Click on the answer to see if you were right. The letter you chose may be different, but that will not matter. Look at privious slide if you are not sure. In mice black fur is dominant over white fur. Predict the genotype and phenotype of a cross between a purebred black furred mouse with a purebred white furred mouse. If brown eyes are dominant over blue eyes in Huskies predict the genotype and phenotype of a cross beween a hybrid brown eyed husky and a blue eyed husky.

13. Now that you have the cross you can create the punnett square. So far you have picked the letter, labeled the dominant/recessive, and found the cross. Now we will label and fill in the punnett square to figure out what possibilities are for the offspring. Click on the word problem to start. Next click step 1 and then step 2. In mice black fur is dominant over white fur. Predict the genotype and phenotype of a cross between a purebred black furred mouse with a purebred white furred mouse. B = Black Fur b = White Fur BB X bb 1st take one of the parents letters and write them along the left side of the boxes. I have circled the BB for parent 1 and moved them over to the box b b 2nd take the other parent and write their genotype letters along the top of the boxes. B B So far you have completed this. Problem Step 1 Click Here Step 2 Click Here

14. Below is what you have so far and how to fill in the chart. Keep clicking on the word cross until the punnett square is filled in. This shows you how to fill in a punnett square. Pay close attention. Cross Parent 2 B = Black Fur b = White Fur BB X bb b b B B b b B Parent 1 B b B b B Click on sound icon to hear explanation Possible genotypes and phenotypes of offspring.

15. Parent 2 t t T Parent 1 t Parent 2 t t Tt Tt T Parent 1 tt tt t See if you can fill in the letters to the punnett square below correctly. Click on the word answer to see if you are correct. Tt X tt

16. The last part of to creating a punnett square is finding the genotype and phenotype of the possible offspring. Below is an example of gene makeup and appearance of parents and possible offspring. To get the genotype you look at the letters of the possible offspring. In this case all of the offspring have Bb, so they are all hybrid. The phenotype is the color of their fur and in this case all of the offspring will have black fur, since they are all hybrid and black fur is dominant. All of their offspring will carry the trait for white fur, but it will not show through. Click on the sound icon at the bottom for explanation. b b B B b b B B b B b B In mice black fur is dominant over white fur. Predict the genotype and phenotype of a cross between a purebred black furred mouse with a purebred white furred mouse. Parents B = Black Fur b = White Fur BB X bb Genotype 100% Hybrid black Phenotype 100% Black Fur Possible Offspring

17. Parent 2 R r Rr R RR Parent 1 rr Rr r Find the genotype and phenotype for the following problem. Now remember to look at the offspring to determine the genotype and phenotype. There are 4 boxes so each box stands for 25%. R = round r = wrinkled Rr X Rr Genotype 25% Purebred round 50% Hybrid round 25% Purebred wrinkled Phenotype 75% Round 25% Wrinkled

18. Below is an exact example of how to set up a punnett square. When you are writing it on you paper it show be set up like this. The punnett square is always on the right and the information is always on the left. I have numbered the steps 1-4 so you know the order to solve the problem. Click on each black number in order to see the explanation. Last click on sound icon near the bottom to hear explanation. • Pick you letters and make sure the dominant is capital 2. Write the cross of the parents 3. Create the punnett square. 4. Find the genotype and phenotype of the offspring using the punnett square. In mice black fur is dominant over white fur. Predict the genotype and phenotype of a cross between a hybrid black furred mouse with a purebred white furred mouse. 1 B = Black Fur b = White Fur BbXbb 3 2 b b Genotype 50% Hybrid black 50% Purebred white 4 B B b b B Phenotype 50% black fur 50% white fur b b b b b

19. Complete the problem below. Click on the sound icon, near the bottom, for a quick overview on the steps. Do not click on the answer until you have completed the entire problem. Remember to follow the steps from the previous slide. The letter you chose might be different then mine, but as long as you follow the rule it doesn’t matter. R = Red r = White Rr x Rr Genotype 25% Purebred red 50% Hybrid red 25% Purebred white Phenotype 75% Red 25% White R r Rr R RR rr Rr r In roses the color red is dominant over white . Predict the genotype and phenotype of a cross between two hybrid red roses.

20. Complete the following problem on a sheet of paper. Click on the sound icon for an explanation. Make sure you use all four steps to answer the problem. Set up your problem so that it looks like the punnett on the previous slide. Bring it up to me to correct. If brown eyes are dominant over blue eyes in huskies predict the genotype and phenotype of a cross between a hybrid brown eyed and a purebred blue eyed.