In a small population of people (a village, lets say) only a small percentage of
ID: 98711 • Letter: I
Question
In a small population of people (a village, lets say) only a small percentage of people can NOT taste PTC and the rest could. All of the people in that population who could taste PTC decided to marry other individuals who could ALSO taste it. Feeling dejected, the non-tasters decided to homozygous dominant, and each of them married a woman taster who was heterozygous. Draw a square to show the outcomes of the crosses. l. What will be the genotype and phenotypes of the next generation in the 'taster village'? provide percentages for each. 2. After those children grow up, and begin to have children of their own, what will happen to the percentages of tasters and non-tasters? What will be the genotype and phenotype percentages of the next generation? What evolutionary force is at work here? (Mutation, Gene Flow, Genetic Drift (bottle neck or founder effect), Selection, or some combination?) What would be the genotype and phenotype possible for the new (non-taster) village if they also decided to only marry each other?Explanation / Answer
Please find the answers below:
Answer 1:
Part 1: Let us assume that the gene for tast is given by T and that for non taste is given by t. The ability to tase PTC is given by a recessive gene which means that an individual must be homozygous in nature in order to taste PTC. On the other hand, heterozygous or homozygous recessive individuals will not be able to taste it. The information states that non-taster moved to another place where they began to reproduce. These non-tasters must be both, homozygous recessive as well as heterozygous population as well. Thus, assuming the maximum possibility with heterozygous individuals, the cross for first generation will be given by:
Thus, the genotype ratio will be: TT: Tt:tt:: 1:2:1
The phenotype ratio will be: Non-tasters: tasters :: 3:1
The percentages will be: Non tasters : 3/4*100 or 75% and tasters : 1/4*100= 25%
Part 2:
When these offsprings grow and further reproduce, the relative number of the tasters in the population will began to slowly increase. Considering the maximum chances of tasters in the population as a cross between two heterozygous populations, i.e. Tt and Tt, we can again have a square as given by:
Thus, the genotype ratio will be: TT: Tt:tt:: 1:2:1
The phenotype ratio will be: Non-tasters: tasters :: 3:1
The percentages will be: Non tasters : 3/4*100 or 75% and tasters : 1/4*100= 25%
This clearly suggests that the population of the tasters will begin to slowly increase by each generation in these individuals.
Answer 2: According to the information, the population of non-tasters was intentionally moved out of the native place and resided and reproduced at a new location to set their population of own. However, this new set of population was undoubtedly related and descended from the original population and indeed displayed the geneotypes and phenotypes in subsequent generations. This suggests that this was founder-effect which acted as an evolutionary force in this scenario.
Answer 3: If the new villagers also decided to marry only non-tasters, there can be two scenarios, i.e. two types of crosses:
Cross 1:
Genotype: All TT
Phenotype: all non-tasters
Cross 2: TT* Tt
Genotype: TT: Tt :: 1:1
Phenotype: All non-tasters
T t T TT Tt t Tt tt