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DIHYBRID CROSSES
(2
Mendel also asked the question?
traits)
Does the gene that determines if a seed
is round or wrinkled have anything to
do with the gene for seed shape?
Must a seed that is yellow
also be round?
http://mac122.icu.ac.jp/BIOBK/BioBookgenintro.html
Figure 11-10 Independent Assortment in Peas
MAKING A CROSS with
TWO gene traits
___________________=
____________________
DIHYBRID
CROSS
Section 11-3
A Punnett square for a
DIHYBRID CROSS
looks like this:
LET’S MAKE A DIHYBRID CROSS
HOMOZYGOUS
YELLOW ROUND
RRYY
HOMOZYGOUS
GREEN WRINKLED
ASSORTMENT
LAW OF INDEPENDENT
__________________________
the factors are distributed to gametes
independently of other factors
rryy
1. Figure
___________
out
what _________________
parent alleles
are
2. Choose
________correct__________
Punnett square __________
size
3. Put
______
in possible_______________________
parent gametes
4. Fill
______
in boxes with _____________________
offspring combinations
5. Determine ____________of_____________&
probabilities phenotypes
____________
genotypes
Image modified from:
http://anthro.palomar.edu/mendel/mendel_1.htm
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PRACTICE MAKING GAMETES
PRACTICE MAKING GAMETES
WHAT ARE THE POSSIBLE GAMETES
THIS PARENT CAN MAKE?
HOMOZYGOUS
ROUND YELLOW
WHAT ARE THE POSSIBLE GAMETES
THIS PARENT CAN MAKE?
Each gamete should
get one of each kind
of gene
Each gamete should
get one of each kind
of gene
HOMOZYGOUS
WRINKLED GREEN
RRYY
RY
RY
rryy
RY
RY
___________ ____________ _____________ _____________
ry
ry
PRACTICE MAKING GAMETES
ry
WHAT ARE THE POSSIBLE GAMETES
THIS PARENT CAN MAKE?
HETEROZYGOUS
ROUND YELLOW
Each gamete should
get one of each kind
of gene
RrYy
RY
Ry
rY
ry
ry
___________ ____________ _____________ _____________
ry
ry
ry
ry
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
___________ ____________ _____________ _____________
RrYy genotype
100% of offspring = _______
ROUND YELLOW
_______________________
phenotype
MAKE ANOTHER CROSS
HETEROZYGOUS
ROUND YELLOW
X
POSSIBLE PARENT GAMETES?
HETEROZYGOUS
ROUND YELLOW
RY
RrYy
Ry
rY
ry
RrYy
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RY
Ry
RRYy
rY
ry
RrYY
RrYy
9 Round &
____
Yellow
3 Round &
____
green
RY
RRYY
Ry
RRYy
RRyy
RrYy
Rryy
rY
RrYY
RrYy
rrYY
rrYy
3 Wrinkled
____
& yellow
ry
RrYy
Rryy
rrYy
rryy
1 wrinkled
____
& green
heterozygous dihybrid
Sign of a ______________________
cross is a
9:3:3:1
_____________ ratio in offspring.
____
9 ____________
dominant TRAIT 1 ; ____________
dominant TRAIT 2
3 ____________
dominant TRAIT 1; _____________
recessive
____
TRAIT 2
____
recessive TRAIT 1; _____________
dominant TRAIT 2
3 ____________
____
TRAIT 2
1 ____________
recessive TRAIT 1; _____________
recessive
9:3:3:1
__________ratio
is a clue that it’s a
____________________________cross
HETEROZYGOUS TWO gene
What are the possible gametes?
RRTT
pure round & pure tall = __________
PRACTICE MAKING GAMETES
for DIHYBRID CROSSES
____
R T ____
R T _____
R T ______
RT
What gametes can it produce?
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html
TtRR
= __________
Heterozygous Tall
& pure round
R _____
tR
____
T R T____
t R ______
What gametes can it produce?
What are the possible gametes?
Hybrid tall
& pure wrinkled
Ttrr
= __________
What are the possible gametes?
T r _____
tr
____
______
T r ____
tr
What gametes can it produce?
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What are the possible gametes?
TtRr
= __________
Heterozygous tall
& hybrid round
Tr
tr
____
T R ____ _____
t R ______
What gametes can it produce?
4