Question

The most obvious outcome of the reproduction process is the generation of individuals of similar design, but in sexual reproduction they may not be exactly alike. The resemblances as well as differences are marked. The rules of heredity determine the process by which traits and characteristics are reliably inherited. Many experiments have been done to study the rules of inheritance.

1. Why an offspring of human being is not a true copy of his parents in sexual reproduction? 
2. While performing experiments on inheritance in plants, what is the difference between F₁ and F₂ generation?
3. (A) Why do we say that variations are useful for the survival of a species over time?
   OR
   (B) Study Mendel's cross between two plants with a pair of contrasting characters.
   

   RRYY	× rryy
   Round Yellow	Wrinkled Green

   He observed 4 types of combinations in F₂ generation. Which of these were new combinations? Why do new features which are not present in the parents, appear in F₂ generation?

Answer 1

1. In sexual reproduction, a human's offspring is not a true replica of his parents because the genetic material from the mother's and father's gametes is mixed together in humans. So, in addition to some new recombination, the offspring has traits from both parents.
2. The selected people are crossed to create the F₁ generation, which is the first generation. The F₂ generation is the second one created through the mating of any two members of the F₁ generation.
3. (A) Over time, variations can help a species survive because they give natural selection the starting point from which to work. Any population will always have some variation, and this variation may be advantageous, neutral, or harmful to an individual's chance of surviving.
   OR
   (B) Yellow and wrinkled seeds and round and green seeds were two novel combinations. These emerge in the F₂ generation as a result of novel combinations of recessive traits whose alleles were present in the F₁ generation but unable to express themselves. In F₂, they appeared by combining in a different way.