PUNNETT SQUARE PRACTICE #3
IN PEAS:
R = round
r=wrinkled
T= tall
t = short
Y = yellow peas
y = green peas
P = purple flowers
p = white flowers
HOMOZYGOUS DIHYBRID CROSSES:
Cross:
HOMOZYGOUS TALL
and ROUND
genotypes:
gametes:
__ __ __ __
__ __ , __ __ , __ __ , __ __
X
PURE SHORT
and WRINKLED
x
__ __ __ __
&
__ __ , __ __ , __ __ , __ __
Probability:
TALL & ROUND
___/16
TALL & WRINKLED
___/16
SHORT & ROUND
___/16
SHORT & WRINKLED
___/16
Use colored pencils to color in boxes of offspring with the same phenotype.
PATTERN FOR HOMOZYGOUS DIHYBRID CROSSES:
If you cross plants that are PURE DOMINANT for TWO TRAITS with plants that are
PURE RECESSIVE for TWO TRAITS, ________ % of the offspring will look
DOMINANT for BOTH traits and the ___________________ traits will not show at all.
HETEROZYGOUS DIHYBRID CROSSES:
Cross:
HETEROZYGOUS
TALL ROUND
genotypes:
gametes:
__ __ __ __
__ __ , __ __ , __ __ , __ __
X
HYBRID
TALL ROUND
x
&
__ __ __ __
__ __ , __ __ , __ __ , __ __
Probability:
TALL & ROUND
___/16
TALL & WRINKLED
___/16
SHORT & ROUND
___/16
SHORT & WRINKLED
___/16
Use colored pencils to color in boxes of offspring with the same phenotype.
PATTERN FOR HETEROZYGOUS DIHYBRID CROSSES :
If you cross 2 parent plants that are BOTH HETEROZYGOUS for TWO TRAITS, the
offspring will show a ____ : ____ : ____ : ____ phenotypic pattern.
Fill in the blanks below with: DOMINANT or RECESSIVE
9/16 of the offspring will show both ___________________ traits.
3/16 will look _________________ for trait 1 and _________________ for trait 2.
3/16 will look __________________ for trait 1 and _________________ for trait 2.
1/16 will look ____________________ for both traits.
Gone with the Wind Genetics
Rhett Butler and Scarlett O’Hara are expecting a baby. Rhett’s rich uncle has
promised them $1 million if their baby has blue eyes and is a boy to carry on the family
name. Brown eyes (B) are dominant over blue eyes (b). Rhett has brown eyes.
What genotype does a baby need to be a blue eyed boy? __ __ __ __
Cross:
Rhett’s Genotype
BbXy
gametes:
__ __ , __ __ , __ __ , __ __
Scarlett’s Genotype
bbXX
&
__ __ , __ __ , __ __ , __ __
Probability:
Brown eyed boys
___/16
Brown eyed girls
___/16
Blue eyed girls
___/16
Blue eyed boys
___/16
Why does this cross not follow the 9:3:3:1 pattern for DIHYBRID (2 gene) crosses?
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