Biology
In Mendel's experiments, tall pea plants (T) are dominant over dwarf pea plants (t).
(i) What is the phenotype and genotype of the F1 generation if a homozygous tall plant is crossed with a homozygous dwarf plant?
(ii) Draw a Punnett square board to show the gametes and offspring when both the parents are heterozygous for tallness.
(iii) What is the Phenotypic ratio and genotypic ratio of the above cross in (ii)?
(iv) State Mendel's Law of Dominance.
(v) What is a Dihybrid Cross?
Genetics
ICSE 2019
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Answer
(i) Phenotype → Tall plants
Genotype → Heterozygous tall plants
(ii) Below is the Punnett square board showing the gametes and offspring when both the parents are heterozygous for tallness:
| T | t | |
| T | TT | Tt |
| t | Tt | tt |
(iii) Phenotypic ratio = 3:1
Genotypic ratio = 1:2:1
(iv) Mendel's Law of Dominance — Out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed. The one that expresses is the dominant character and the one that is unexpressed is the recessive. The recessive character can express only when the pair consists of both recessives (homozygous recessive).
(v) The cross in which two features of an organism / plant are taken together at a time.
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