Q. 775.0( 2 Votes )
A person first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only A-B type of seeds were produced in the F1generation. When F1 generation pea plants having A-B type of seeds were cross-bred by self-pollination, then in addition to the original round-yellow and wrinkled-green seeds, two new varieties A-D and C-B type of seeds were also obtained.
(a) What are A-B type of seeds?
(b) State whether A and B are dominant traits or recessive traits.
(c) What are A-D type of seeds?
(d) What are C-B type of seeds?
(e) Out of A-B and A-D types of seeds, which one will be produced in
(i) minimum numbers, and
(ii) maximum numbers, in the F2 generation ?
Round yellow- RRYY, wrinkled green-rryy. On crossing these two pea plants we get RrYy combination which has dominant gene R for Round shape and Dominant gene Y for yellow color. Hence A-B types of seed produced as a result of the first cross are Round yellow.
(b) A and B are dominant traits since they are Round (R) and yellow (Y)
When RrYy obtained in the first generation is self-pollinated, the new varieties obtained are RY, Ry, rY, ry; where RY- Round yellow, Ry-Round green, rY-Wrinkled yellow, and ry- wrinkled green. Since A-B type of seed is Round and yellow, therefore A-D type of seed is Round and Green.
When RrYy obtained in the first generation is self-pollinated, the new varieties obtained are RY, Ry, rY, ry; where RY- Round yellow, Ry-Round green, rY-Wrinkled yellow, and ry- wrinkled green. Since A-B type of seed is Round and yellow, therefore C-B type of seed is wrinkled and yellow.
(e)(i) A-D (Round and green ‘Ry’ will be produced in minimum number)
(ii) A-B (Round and yellow ‘RY’ will be produced in maximum number in F2 generation)
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