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DO NOW. Get out your monohybrid crosses HW A woman with a widow’s peak (heterozygous) has children with a man who does not have a widow’s peak. What is the probability they will have a child without a widow’s peak?. Dihybrid Crosses. Crosses that involve two traits - PowerPoint PPT Presentation
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DO NOW
1. Get out your monohybrid crosses HW2. A woman with a widow’s peak
(heterozygous) has children with a man who does not have a widow’s peak. What is the probability they will have a child without a widow’s peak?
Dihybrid Crosses
• Crosses that involve two traits• Similar to monohybrid crosses, but HARDER!
A pea plant that is heterozygous for round, yellow seeds is self fertilized . What are the genotypic and phenotypic ratios of the plant’s offspring?
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring?
• Step 1: Write the symbolsR = Roundr = smoothY = Yellowy = green
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring?
• Step 2: Determine the parental genotypes and write the parental Cross.
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring?
• Step 3: Determine the gametes. (kind of like the FOIL method from math class)– Combine the R’s and Y’s for each parent to
determine the alleles for each egg or sperm.
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and
phenotypic ratios of the plant’s offspring?• Step 4: Set up a large 4x4 Punnet square,
place one gamete set from parent 1 on the top and one gamete set from parent 2 on the side.
RY Ry rY ry
RYRy
rY
ry
Gametes – Parent #1
Gam
etes
– P
aren
t #2
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and
phenotypic ratios of the plant’s offspring?• Step 5: Fill in the Punnett Square.
RY Ry rY ry
RYRy
rY
ry
Gametes – Parent #1
Gam
etes
– P
aren
t #2
RRYYRrYyRrYY RrYy
Rryy
rrYy
rryy
RRYy
RRyy
RrYy
Rryy rrYy
rrYY
RRYy
RrYY
RrYy
A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and
phenotypic ratios of the plant’s offspring?• Step 6: Determine the number of offspring for
each phenotype (phenotypic ratio).
RY Ry rY ry
RYRy
rY
ry
Gametes – Parent #1
Gam
etes
– P
aren
t #2
RRYYRrYyRrYY RrYy
Rryy
rrYy
rryy
RRYy
RRyy
RrYy
Rryy rrYy
rrYY
RRYy
RrYY
RrYy
___ round & yellow: ___round & green:___ wrinkled & yellow: ___ wrinkled and green 9 3 3 1
Dihybrid Cross
Practice!
• Cross a plant that is heterozygous round and heterozygous yellow with a plant that is wrinkled and green.
Cross a plant that is heterozygous round and heterozygous yellow with a plant that is wrinkled and green.
SYMBOLSR = Roundr = smoothY = Yellowy = green
Parental Cross:
Phenotypic Ratio:4 round & yellow4 round & green4 wrinkled & yellow4 wrinkled & green
1:1:1:1
