A flower speeds undergoes normal segregation and independent assortment. A genet
ID: 85512 • Letter: A
Question
A flower speeds undergoes normal segregation and independent assortment. A geneticist decides to cross one plant homozygous dominant for height, seed color, and petal size, with one that is heterozygous for height and homozygous recessive for seed color and petal size (consider this the P_1 generation). If two genotypically-different plants of the resulting F_1generation are crossed (F_1A times F_18), what is the probability that an F_2 plant is homozygous dominant for height, seed color, and petal size?Explanation / Answer
Answer is 0.042
Let genotype of plant homozygous dominant for height, seed color and petal size be HHCCSS. All gametes from this plants have HCS genotype.
Let genotype of plant heterozygous for height, homozygous recessive for seed color and petal size be Hhccss. This one produces two tgypes of gametes in equal proportion. Those are Hcs and hcs.
The cross between the above parents, therefore, result in equal proportion of F1 plants with HHCcSs and HhCcSs, in equal proportion.
HHCcSs plant gives following types of gametes.
HCS
HCs
HcS
Hcs
HhCcSs plant gives following gametes
HCS
HCs
HcS
Hcs
hCS
hCs
hcS
hcs
One parent gives 4 types of gametes and the other gives 8 types.
We want to know probability of getting plant homozygous dominant for height, seed color and petal size in this cross.
There will be 8 x 4 = 24 genotypic combinations possible in off springs.
For a plant with homozygous dominant for all three loci, both gametes should be having dominant alleles.
If we look at the list of the gametes, each parent produces only one gametes with HCS allele combination.
So, out of 24 off springs of this cross, only one will be HHCCSS.
The probability is 1/24 = 0.042
We can also cross check this with checkered board.
HCS
HCs
HcS
Hcs
HCS
HHCCSS
HHCCSs
HHCcSS
HHCcSs
HCs
HHCCSs
HHCCSs
HHCcSs
HHCcss
HcS
HHCcSS
HHCcSs
HHccSS
HHccSs
Hcs
HHCcSs
HHCcss
HHccSs
HHccss
hCS
HhCCSS
HhCcSs
HhCcSS
HhCcSs
hCs
HhCCSs
HhCCss
HhCcSs
HhCcss
hcS
HhCcSS
HhCcSs
HhccSS
HhccSs
hcs
HhCcSs
HhCcss
HhccSs
Hhccss
As expected one out of 24 off springs have HHCCSS genotype.
HCS
HCs
HcS
Hcs
HCS
HHCCSS
HHCCSs
HHCcSS
HHCcSs
HCs
HHCCSs
HHCCSs
HHCcSs
HHCcss
HcS
HHCcSS
HHCcSs
HHccSS
HHccSs
Hcs
HHCcSs
HHCcss
HHccSs
HHccss
hCS
HhCCSS
HhCcSs
HhCcSS
HhCcSs
hCs
HhCCSs
HhCCss
HhCcSs
HhCcss
hcS
HhCcSS
HhCcSs
HhccSS
HhccSs
hcs
HhCcSs
HhCcss
HhccSs
Hhccss
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