Numerical Problems/ISC/Class 12
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Numerical Problems - Mendelian Crosses
Here are some numerical problems based on the principles of inheritance and variation, along with their solutions.
In pea plants, the allele for tallness (T) is dominant over the allele for dwarfness (t). A heterozygous tall plant is crossed with a dwarf plant. What will be the phenotypic and genotypic ratio of the offspring?
Solution:
| T | t | |
|---|---|---|
| t | Tt | tt |
In pea plants, round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A plant that is heterozygous for both traits is self-pollinated. What is the probability of obtaining an offspring that is homozygous recessive for both traits?
Solution:
rr from a Rr x Rr cross is 1/4.yy from a Yy x Yy cross is 1/4.rryy = (Probability of rr) x (Probability of yy) = (1/4) x (1/4) = 1/16.Therefore, the probability of obtaining an offspring that is homozygous recessive for both traits is 1/16.
In snapdragons, flower color is an example of incomplete dominance. The allele for red flowers (R) is incompletely dominant to the allele for white flowers (r). The heterozygous genotype (Rr) results in pink flowers. If two pink-flowered snapdragons are crossed, what are the expected phenotypic and genotypic ratios in the offspring?
Solution:
| R | r | |
|---|---|---|
| R | RR | Rr |
| r | Rr | rr |
A man with blood group A marries a woman with blood group B. They have a child with blood group O. What are the genotypes of the parents and the child? What is the probability of them having a child with blood group AB?
Solution:
ii), they must inherit an i allele from each parent.i allele.| IA | i | |
|---|---|---|
| IB | IAIB | IBi |
| i | IAi | ii |
Hemophilia is an X-linked recessive disorder. A man with normal blood clotting marries a woman who is a carrier for hemophilia. What is the probability of their children having hemophilia?
Solution:
| XH | Y | |
|---|---|---|
| XH | XHXH | XHY |
| Xh | XHXh | XhY |
Offspring Genotypes and Phenotypes:
Probability:
/Numerical-Problems/ISC/Class-12/Unit_2_Chapter_1_Principles_of_Inheritance_and_Variation_Numerical_Questions.mdx