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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.
