Q77 of 167 Page 195

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 ?

(a)Round Yellow.

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)


(c) Round-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 A-D type of seed is Round and Green.


(d) Wrinkled-yellow


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)


More from this chapter

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75

A man with blood group A marries a woman with blood group 0 and their daughter has blood group 0. Is this information enough to tell you which of the traits - blood group A or 0 -is dominant? Why or why not?

 76

A Mendelian experiment consisted of breeding tall TT pea plants bearing violet flowers with short t pea plants bearing white w flowers. The progeny all bore violet W flowers, but almost half of them were short. This suggested that the genetic make-up (or genotype) of the tall parent can be depicted as:

(a) TTWW


(b) TTww


(c) TtWW


(d) TtWw


Give reason for your choice

 78

The person A has only B chromosomes in all its gametes. On the other hand, another person C has chromosome D in half of gametes and chromosome E in the other half of gametes. When chromosomes B and D combine during fertilization, a female zygote results. On the other hand, combination of B and E chromosomes produces a male zygote.

(a) What are chromosomes?


(i) B


(ii) D, and


(iii) E ?


(b) Out of B, D and E, which two chromosomes are of the same type?


(c) Which chromosome is smaller in size?


(d) What is the general name of chromosomes such as B and E?


(e) Out of the two persons A and C, which one is


(i) male, and


(ii) female ?

 79

Mendel first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the F1 generation. When F1 generation pea plants having round-yellow seeds were cross-bred by self-pollination, then peas having round � yellow seeds, round green seeds, wrinkled-yellow seeds and wrinkled-green seeds were produced. Mendel collected a total of 2160 seeds.

(a)What will be the number of?


(i) Round green seeds


(ii) Wrinkled green seeds


(iii) Round yellow seeds, and


(iv) Wrinkled-yellow seeds


(b) Which 'ratio' as established by Mendel have you made use of in answering the part (a) above?