2. The following two problems are from the website: http:/biology.cle.uc.edu/cou

Question

2. The following two problems are from the website: http:/biology.cle.uc.edu/courses/bio105/geneprob.h You can find good tutorials on the website for the genetics problems. S points) ere is a gene that controls formation (or lack thereof) of muscles in the tongue that allow e people who lack those muscles cannot roll their In humans, th people with those muscles to roll their tongues, whil tongues. The ability to roll one's tongue is dominant over non-rolling. The ability to taste certain substances is also genetically controlled. For example, there is a substance called phenylthiocarbamate (PTC for short), which some people can taste (the dominant trait), while others cannot (the recessive trait). The biological supply companies actually sell a special kind of tissue paper impregnated with PTC so students studying genetics can try tasting it to see if they are tasters or non-tasters. To people who are tasters, the paper tastes very bitter, but to non-tasters, it just tastes like paper. Let's let R represent tongue-rolling, r represent a non-roller, T represent ability to taste PTC, and t represent non- tasting. Suppose a woman who is both a homozygous tongue-roller and a non-PTC-taster marries a man who is a heterozygous tongue-roller and is a PTC taster. Draw the Punnett square that predicts what their children will be.

Explanation / Answer

So our informations from the question are:

R = tongue roller (dominant trait)

r = non-tongue roller (recessive trait)

T = PTC taster (dominant trait)

t = non-PTC taster (recessive trait).

Now the woman has homozygous gene of tongue roller (RR) and non-PTC taster (tt).

and her husband has heterozygous gene of tongue-roller (Rr) and PTC taster (Tt).

So basically this is a two hybrid cross system and according to Mendel's law of independent assortment these genes can assort freely during gamete production.

So the woman' genotype is --> RRtt

and her husband's genotype is --> RrTt

So Their children will all have heterozygous genotype with 100% tongue-roller phenotype and 50% will be PTC taster and 50% will be non-PTC taster.

Woman/Man Rt Rt Rt Rt RT RRTt RRTt RRTt RRTt Rt RRtt RRtt RRtt RRtt rT RrTt RrTt RrTt RrTt rt Rrtt Rrtt Rrtt Rrtt

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