Punnett Squares

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

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

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

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

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.

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.

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

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

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_____________& ____________

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

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

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

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 _______

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)

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

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

B b Try the Cross! B b B B B b B b b b

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

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

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

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

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

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

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

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