Two pea plants - one with round yellow seeds (RRYY) and another with wrinkled green (rryy) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are self-pollinated, which new combination of characters is expected in F2 progeny? How many seeds with these new combinations of characters will be produced when a total 160 seeds are produced in F2 generation? Explain with reason.
Answers
Answer: When the total seeds are 160 then the seeds with these new combinations will be produced in the F2 generation are as follows-
30 seeds will be round & green (RRyy), (RyYy), (Rryy)
30 seeds will be wrinkled & yellow (rrYY), (rrYy), (rrYy)
Explanation:
If we take 2 types of true-breeding pea plants that were different in regard to their 2 characters.
- 1st plant had round & yellow seeds- RRYY
- 2nd plant had wrinkled & green seeds - rryy
- F1 generation- cross the
true-breeding plants to each other RRYY X rryy
↓ ↓
- Gametes RY ry
↓
- Collection of many seeds and RrYy
Phenotype is recorded.
- F1 seeds are planted and grown and then RrYy X RrYy
further are allowed to self-fertilized or
Self-crossed or self-pollinate
producing the seeds of the F2 generation
- Punnett square of F2 generation is attached below
- F1 generation- All seeds were round & yellow seeds
- F2 generation - The phenotypic ratio of the F2 generation will be 9.8: 3.2: 3.4: 1.0, if we count the experimental error then approximated ratio will be 9:3:3:1 (In total 16 combinations are possible by randomly combining male and female gametes).
9- Round & Yellow seeds
3- Round & Green seeds
3- Wrinkled & yellow seeds
1- Wrinkled & green seeds
- F2 generation- If a total of 160 seeds were produced, if we look at the combinations there will be 2 parental combinations and 2 New combinations.
- 2 Parental Combinations will be-
9/16 x 160 = 90-round & yellow seeds (RRYY)
1/16 x 160 = 10- wrinkled & green seeds (rryy)
- 2 New combinations will be -
3/16 x 160 = 30- round & green seeds
3/16 x 160 = 30- wrinkled & yellow seeds
- The reason for the 2 new combinations is because of independent assortment as round-green and wrinkled-yellow shows that the genes for the shape & color of the seeds are assorted independently
- This can also explain that independent assortment is based on the dihybrid cross in which if we are studying the inheritance of more than 1 character simultaneously, then the factors or genes for each character assort out independently to the other gene or factor.
When F1 plants are self-pollinated, then the new combination of characters is expected in F2 progeny are 30 seeds of round and green and 30 seeds of wrinkled and yellow.
When a total 160 seeds are produced in F2 generation (9:3:3:1), then
two Parental combinations :-
90 round and yellow and 10 wrinkled and green seeds
two New combinations :-
30 round and green and 30 wrinkled and yellow seeds.
Hope it helps u