Mendel took purebreeding tall plants & crossed them topurebreeding short plants
ID: 4912 • Letter: M
Question
Mendel took purebreeding tall plants & crossed them topurebreeding short plants to obtain an F1 generation composedcompletely of tall plants. He then crossed the F1 plants toeach other & observed a 3:1 ratio of tall: short plants in theF2 generation. If the tall F2plants are back crossed to the purebreeding short parent,what is the probability that a short plant will be observed?Please help me!!!! I can't figure out why the correctanswer is 1/3. Thank you.
Please help me!!!! I can't figure out why the correctanswer is 1/3. Thank you.
Explanation / Answer
pure breeding tall plants & crossed them to purebreedingshort plants
TT X tt
TT t t-gametes
Tt-----------tall plants-----------F1 GENERATION
T
T
t
Tt
Tt
t
Tt
Tt
Tt x Tt
T
t
T
TT
Tt
t
Tt
tt
TT,Tt -TALLPLANTES
tt-SHORT
3:1RATIO
If the tall F2 plants are backcrossed to the purebreeding short parent, what is theprobability that a short plant will be observed
TT, tall F2plants X tt
All offspring are all
Tt tall F2plants X tt
T
t
t
Tt
Tt
t
Tt
tt
Answer : 25% for short plant- (1/4)
T
T
t
Tt
Tt
t
Tt
Tt