Punnett Squares

Wednesday!

Bell Ringer: Objective:• Predict the offspring of a

cross in a Punnett Square

AGENDA1. Independent Reading

2. Notes on Punnett Squares

3. Practice Punnett Squares4. 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 =

____________________

A Punnett square for a MONOHYBRID CROSS looks like:

MONOHYBRID CROSSONE GENE

PUNNETT SQUARESare used to show possible offspring

from a cross between 2 parents

_______________ go at top and on left side

Boxes show _______________________________

T T

T

t

possible offspring combinations

Parent alleles

1. ___________ what _________________ are2. ________correct__________ square __________3. ______ possible_______________________4. ______ boxes with _____________________5. Determine ____________of_____________& ____________

STEPS FOR MAKING CROSSES

Figure out parent allelesChoose Punnett size

Put in parent gametesFill in offspring combinations probabilities phenotypes

genotypes

IN PEA PLANTS

Tall is dominant over short TALL = ____

SHORT = ____T

tLET’S MAKE A CROSS!

PURE TALL PURE SHORTX

PURE TALL parentWhat are the parent alleles?

T T

T T

HOMOZYGOUS

What gametes can it make?

PURE SHORT parent What are the parent alleles?

t t

t t

HOMOZYGOUS

What gametes can it make?

GENOTYPE _____ PHENOTYPE _______

_____ of the offspring

____ % ___/4 will be

_______

T T

t

t

T t T t

T t T t

Tt TALL

ALL

1004

TALL

Let’s Try Again!

Brown eyes is dominant over green eyes

BROWN EYES = ____GREEN EYES = ____

Bb

LET’S MAKE A CROSS!Heterozygous brown (mom) Heterozygous brown (dad)

Mom-Heterozygous BrownWhat are the parent alleles?

B b

B b

HETEROZYGOUS

What gametes can it make?

Dad-Heterozygous BrownWhat are the parent alleles?

B b

B b

HETEROZYGOUS

What gametes can it make?

Try the Cross!

B b

B

b

B B B b

B b b b

_____

of the offspring ____ % ___/4will have _________

GENOTYPES _______ PHENOTYPES _______________

_______ _______________

_______ _______________

WHAT ARE THE POSSIBLE…

_____

of the offspring ____ % ___/4 will have _________

BbBB

253

75

13

brown eyes1

green eyes

bb Green eyes

Brown eyes

Brown eyes

EXIT TICKET• Complete a punnett square. The mother is

heterozygous for brown hair and the father is homozygous dominant for brown hair.

Mother = Bb

Father = BB

B b

B

B

BB Bb

BB Bb

Genotype = 2/4 BB 2/4 Bb

Phenotype = 4/4 Brown hair

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

Review:

• Take out a sheet of paper • Follow along with the next few slides to

review

Homozygous or Heterozygous• Gg

• kk

• YY

• Aa

• Heterozygous

• Homozygous Recessive

• Homozygous Dominant

• Heterozygous

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

Critical Thinking1) 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?

Punnett Square Challenge

• Work with one partner to complete the Punnett Square Challenge

• Make sure to get a stamp where indicated.