Please help me understand this!!!?

Question

BIOLOGY 1108 EVOLUTION AND POPULATION GENETICS

Variations on the ability to taste PTC have no obvious survival value, and yet there is ethnic variation in allele frequencies between different groups. For instance, 63% of Arabs are tasters for PTC, whereas 63% of native Americans can't taste it. At least one condition of the Hardy-Weinberg Theory was not met respect to the gene in the world populations.

1. How do you think this ethhnic variation came about?

2. How could this variation in allele frequency be associated with survival potential of the ability to detect a bitter taste?

3. Assuming there was no selective advantage for this traitt, what other factor might account for the ethnic differences?

This is my homework. Its not for a grade for right or wrong but for effort and I am having a little trouble with this. Does anyone know about this stuff if so please help me. Even though the grade is for effort I still want to understand it so I'll do good on the test. Thank you

Yeah I know

Answer 1

1. It could be related to the quality of the water supply. Bitterness can be associated with the quality of water. Native Americans enjoyed a more plentiful and flowing water supply than did the Arabs.

2. The bitterness sensation may have been associated with the survival needs to distinguish poisons in the water.

3. If you consider the factors that affect the development of taste have more than survivability on the surface. For example, it may be social acceptance by learning to like the foods prepared by the group. Since the group is necessary for survival, fitting in became important as a genetic imperative.

Now you separate the Arabs and Native Americans by the cuisine they had available, along with the cultural differences in how food is prepared and seasoned. Middle Eastern food is very different in the way spices are applied than what Native Americans used. Native Americans had a plentiful supply of vegetables, grains and meats available to them. Arabs on the other hand at many more meats and cheeses. Learning to like the food available led to their taste development.

Answer 2

Just a guess but by the sound of it the location of where the people were living at the time may have been an issue (saying that the ptc compound was located in an area then the people there would have learned to taste ptc) while in other areas this compound may not have been around as much and therefore not had any experience to be able to learn this trait (everything you taste or experience is learned) - for people to taste something that is bitter and possible uncomfortable is learned and therefore programmed in the genetic map.

Answer 3

Taste Receptor: Phenylthiocarbamide


Differences in the ability of humans to taste the sulfur-containing compound phenylthiocarbamide were first reported in the 1930s. PTC tasters find even low concentrations of the compound extremely bitter, while nontasters report little or no taste to the same concentration of PTC. The ability to taste PTC is inherited as a dominant trait. More precise analysis of the phenotype indicated that the "taster" gene is incompletely dominant to the "nontaster" gene, so that people with two copies of the taster gene have a lower threshold of sensitivity to PTC than people with only one copy. PTC is not a natural product, but similar sulfur-containing compounds are found in plants of the mustard family. Some of these compounds interfere with iodine metabolism, so the ability to taste them may confer some protection against thyroid disorders.

Although the trait has been a favorite standby for genetics classes for over 70 years, its chromosomal location and gene sequence were reported only in 2003 by Kim and others. The gene is one of many taste receptor proteins encoded by a large family of genes on the long arm of human chromosome 7 at positions q35-36. The taster condition is most strongly associated with the "PAV" haplotype, that is, the highest sensitivity to PTC is found in individuals with the amino acids Proline, Alanine and Valine at positions 49, 262 and 296 respectively in the protein. Most nontasters have the amino acids A, V and I at these three positions. The sequence reported by Kim is below. The protein appears to be a G-protein-coupled transmembrane protein. Seven helical regions wind back and forth through the membrane. These transmembrane regions are marked in the sequence below, as are the positions of the amino acids of the PAV haplotype.

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How did it come about - how about that mustard grows in the middle east?

Survival - maybe there is a poisonous plant that tastess similar that grows in the region, and not in NA, where native american's live.

The presense of those types of bitter plants might sharpen your ability to taste it, even if there's no selective advantage.

Answer 4

http://www.daltonstate.edu/faculty/chumphrey/Biology%201108/Chapter%20Outlines/CHAPTER%2018.html <

Answer 5

how can i help you if i dont under stand it!!