2. In a lizard species, brown body color (b) is recessive to green (B), short ta
ID: 262027 • Letter: 2
Question
2. In a lizard species, brown body color (b) is recessive to green (B), short tail (s) is recessive to long tail (S). You cross a Bb Ss individual with an individual of genotype bb Ss. You know that all genes are autosomal and assort independently. Using the Probability Method answer the following, and show all work.
a. Break the complex cross into simple crosses and show the expected genotypic and phenotypic ratios for each cross.
b. How many different offspring genotypes are expected among the offspring of the cross? Show the calculation.
c. What is the expected proportion of Bb SS offspring? Show the calculation.
d. What is the expected proportion of Green, Short-tail offspring? Show the calculation.
Explanation / Answer
a. Break the complex cross into simple crosses and show the expected genotypic and phenotypic ratios for each cross.
Bb Ss x bb Ss
BS
Bs
bS
bs
bS
BbSS
BbSs
bbSS
bbSs
bs
BbSs
Bbss
bbSs
bbss
3 Green color and long tail= 3/8
1 Green color and short tail=1/8
3 Brown color and long tail=3/8
1 Brown color and short tail=1/8
b. How many different offspring genotypes are expected among the offspring of the cross? Show the calculation.
4 different offsprings are possible based on phenotype,
8 different offsprings based on genotype
c. What is the expected proportion of Bb SS offspring? Show the calculation.
?
d. What is the expected proportion of Green, Short-tail offspring? Show the calculation.
Green color and short tail=1/8
BS
Bs
bS
bs
bS
BbSS
BbSs
bbSS
bbSs
bs
BbSs
Bbss
bbSs
bbss
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