genetics question?

Question

the ability to roll the tongue is dominant. what explanation could ther be for two parents who cannot roll their tongue (recessive) having a child who can roll his/her tongue?



any answers are appreciated

Answer 1

An affair. What you say is impossible genetically, and genetics VERY RARELY lie.

Brokenhearts- 2 parents with brown eyes can have blue eyed children because brown is dominant and the parents can carry the recessive blue trait. It is impossible though for 2 blue eyed parents to have a brown eyed child because blue is recessive and they CANNOT carry the brown gene as in the case of the tougne rolling.

Answer 2

If the parents are heterozygous for the tongue rolling gene that is, they both carry a copy of the dominant gene T and the recessive t. Using Mendelian genetics, each child would have a 25% chance of being homozygous dominant (TT), 50% chance of heterozygous dominant (Tt), and a 25% chance of being recessive (tt). So at least 3/4 of their children would be expressing the Tongue rolling gene and only 1/4 would be recessive.
But, in your example, the two parents are both recessive, that is (tt). So no child of theirs could have the tongue rolling gene unless it was a spontaneous mutation or if the gene was sex linked. So let's pretend the gene is, linked to the x chromosome. So a recessive mother (XtXt) could only contribute an Xt recessive gene to her daughters, but the male (XTY0) could contribute an XT gene. Imagine that another X linked gene would be needed to activate the tongue roll. Therefore any male child, regardless of the gene they inherited, would not be able to tongue roll. But if a XTY0 male had a daughter, then they would be heterozygous for the gene (XTXt) and therefore be able to express the tongue roll.

Answer 3

There is but one answer to this...a genetic mutation! If an allele to the tongue-rolling gene is dominant (I assume heterozygous, so only one allele is enough for the trait to be expressed), then the child bearing such an allele would express the phenotypic counterpart of the allelic pair.

If both parents are homozygous recessive for the tongue-rolling gene, the product, actually their offspring/s, of their mating would result in children who cannot roll their tongues; if in case they can, at some point during the ovulation, prior to the fertilization of the egg, a certain genetic mutation (perhaps a point mutation, frameshift mutation, or even reciprocal translocation depending on the DNA sequence coding for the tongue-rolling gene) enabled the allele (could be one or two of them) to revert to the dominant counterpart, resulting in the gene expression.

Of course, there is a rather low chance of allelic reversion, and this type of mutation could have occured prior to the fertilization of the woman's egg; it could also be attributed to teratogens (agents that cause genetic mutation, resulting in physical deformities), or environmentally induced.

Hope this helps!

Answer 4

each of the parents would carry the recessive trait which they would have inherited by their own parents. thus, if a child receives the recessive trait from both of his or her parents then the child will be able to roll their tongue. this is because there is no dominant trait to "over power" any recessive traits, only two recessive traits so the trait is expressed.

Answer 5

If there are two parents than can't roll their tongues, they are both "rr" if tongue rolling is "RR" or "Rr". If a child must inherit a "R" for them to roll their tongue, both parents cannot have an "R" anywhere. Therefore, if both parents are "rr", their child has a 100% chance of not being able to roll their tongue and being "rr"

Answer 6

Can not remember if tongue rolling is a dominant characteristic but if so one parent is not the parent

Answer 7

if the child can roll their tongue ,then the 2 parents who cant roll their tongue must have a DNA trait to roll their tongue to pass it on to their offspring

Answer 8

1. A back mutation. This is unlikely, but possible.
2. Child was swapped at the hospital. This is unlikely, but more likely than a back mutation.
3. The supposed father isn't the biological father. In America, this sort of thing happens 10% of the time. Much more likely than child swapping or mutation.

Answer 9

Then either the wife committed adultery or the child is not theirs. If the two parents are recessive tt, then they cannot have a child who is either Tt or TT because the dominant trait is not in the parents' genes.

Answer 10

I do not know if this is an answer but it is the same if 2 parents have brown eyes, they may have a child w/ blue eyes, it must be a dominant gene in one or the other of the parents