1. Punnett Squares

2. Wednesday! Bell Ringer: Objective:
Predict the offspring of a cross in a Punnett Square

3. AGENDA Independent Reading Notes on Punnett Squares
Practice Punnett Squares
Exit Ticket

4. Essential Question
What information do I need to know in order to set up a Punnett square?

5. Read Phenotypes and Genotypes 258-259
Stop when you reach “Dihybrid Crosses” on page 259
Take Cornell Notes

6. C.H.A.M.P.s
Conversation: It is expected that you remain silent while you read
Help: Raise your hand for help
Activity: Reading on Punnet squares
Movement: You should remain in your seat
Participation: You are meeting expectations if you are working on your reading.

7. C.H.A.M.P.s
Conversation: It is expected that you remain silent while I lecture
Help: Raise your hand for help
Activity: Notes on Mendel
Movement: You should remain in your seat while I am lecturing
Participation: You are meeting expectations if you are quietly taking notes and asking questions.

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

9. 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

10. 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_____________& ____________

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

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

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

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

15. B b BROWN EYES = ____ GREEN EYES = ____
Let’s Try Again!
Brown eyes is dominant over green eyes
BROWN EYES = ____
GREEN EYES = ____ B b
LET’S MAKE A CROSS!
Heterozygous brown (mom) Heterozygous brown (dad)

16. Mom-Heterozygous Brown What are the parent alleles?
B b
HETEROZYGOUS  
What gametes
can it make? b B

17. Dad-Heterozygous Brown What are the parent alleles?
B b
HETEROZYGOUS  
What gametes
can it make? b B

18. B b
Try the Cross! B b
B B
B b
B b
b b

19. WHAT ARE THE POSSIBLE… Brown eyes BB Bb Brown eyes bb Green eyes 1 3
GENOTYPES _______ PHENOTYPES _______________
_______ _______________
Brown eyes BB Bb
Brown eyes bb
Green eyes 1 3
_____ of the offspring
____ %
___/4
will have _________
_____ of the offspring
____ %
___/4
will have _________ 75 25 3 1
brown eyes
green eyes

20. EXIT TICKET
Complete a punnett square. The mother is heterozygous for brown hair and the father is homozygous dominant for brown hair.
B b
Mother = Bb
Father = BB B BB Bb
Genotype = 2/4 BB 2/4 Bb
Phenotype = 4/4 Brown hair BB Bb

21. Bell Ringer: B b B b BB Bb Bb bb Genotype = ¼ BB 2/4 Bb ¼ bb
Phenotype = ¾ Brown eyes
¼ Green eyes
B b BB Bb Bb bb

22. Review: Take out a sheet of paper
Follow along with the next few slides to review

23. Homozygous or Heterozygous
Homozygous Recessive
Homozygous Dominant Gg kk YY Aa
Cold call

24. Genotype or Phenotype? Rhonda has brown hair Rhonda is BB
Jeffrey is Tt
Jeffrey is tall
Robert is homozygous tall
Jasmine is heterozygous for her dimples
Cold call

25. Critical Thinking
1) Tracy’s mom has green eyes. Her dad’s eyes are dark brown. Tracy and all her brothers and sisters have dark brown eyes. Which allele is recessive?
2) James has a dominant allele for hitch-hiker’s thumb (H) and a recessive allele for not having it (h). He is able to bend his thumb backwards. Is he homozygous or heterozygous?
Popsicle stick

26. Punnett Square Challenge
Work with one partner to complete the Punnett Square Challenge
Make sure to get a stamp where indicated.