The answers would be:
First blank: 3:1
Second blank: 9:3:3:1
Let's try and see how a Punnet Square would look like for each scenario:
<em>MONOHYBRID</em>
<em>Rr x Rr R - Dominant r- recessive</em>
<u> R r </u>
<u>R RR Rr</u> Genotype: Phenotype
<u>r Rr rr </u> RR (1) Dominant Trait
Rr (2) Dominant Trait
rr (1) Recessive Trait
As you can see, you have 3 results out of 4 that will come out as domimant phenotypes, and 1 out of 4 as Recessive Phenotype. We can therefore conclude that the ratio of dominant to recessive is 3:1.
DIHYBRID
RrYy x RrYy
<u> </u><u> RY Ry rY ry</u>
<u>RY </u><u>RRYY RRYy RrYY RrYy</u>
<u>Ry </u><u>RRYy RRyy RrYy Rryy</u>
<u>rY </u><u>RrYY RrYy rrYY rrYy</u>
<u>ry </u><u>RrYy Rryy rrYy rryy</u>
Breaking it down to genotype and phenotype:
Genotype Phenotype
RRYY (1) Dominant:Dominant
RRYy (2) Dominant:Dominant
RrYY (2) Dominant:Dominant
RrYy (4) Dominant: Dominant
RRyy (1) Dominant:Recessive
Rryy (2) Dominant:Recessive
rrYY (1) Recessive: Dominant
rrYy (2) Recessive: Dominant
rryy (1) Recessive:Recessive
Let's look at the four possible phenotype expressions based on our breakdown and count how many combinations we see:
<em>Dominant:Dominant 9 </em>
<em>Dominant:Recessive 3</em>
<em>Recessive:Dominant 3 </em>
<em>Recessive:Recessive 1</em>
So the ratio would be:
9 : 3 : 3 : 1
