Question

Study Questions

• Imagine that you are breeding a specific type of plant or animal and there is a characteristic (a phenotypic trait) that you want your breed to have, but it is a recessive trait in that species and none of the current generation you have to work with display the desired phenotype. Is it possible to devise a breeding plan that will result in that characteristic becoming universal among each subsequent generation?
• Try to imagine a hypothetical breeding population and its gene pool (collectively, all the various alleles present in the whole population) – it doesn’t matter what species you think of; it could be elephants or grasshoppers. Imagine both a huge breeding population (millions of individuals) and a very small one (perhaps just dozens of individuals). Why would the smaller population be more strongly or easily affected by evolutionary processes than the larger one?

Answer 1

To incorporate a desired phenotype that is a recessive trait that is not seen in any of the current generation,backcross breeding plan can be used.Backcross is a cross between the hybrid (F1) with one of its parents.In this hybrid and the subsequent generations are repeatedly backcrossed to one of its parents.To transfer a recessive gene to the generation ,follow the steps:

• A recurrent parent selected as female is crossed with a parent with that characteristic recessive trait.
• F1 obtained is backcrossed to the recurrent parent
• plants that resemble recurrent parents are selected and backcrossed until fourth generation
• In the fifth generation F1 is selfed to produce F2 and plants with recessive trait are identified

Smaller the population size,they are largely affected by random changes or genetic drift.It is the change in allele frequency generation after generation.Therefore in a small population this change will affect more strongly the in a large population as there is only less number of individuals in small population.