Question

whats the validity of the punnett squares in determining paternity for a child?

Answer 1

@Windycity24 They are not valid at all. You cannot reliably use genes and alleles to test paternity. You have to use other things like short tandem repeats, stuff like that. Interestingly, it is not possible to identify the male gamete donor in humans with 100% accuracy. Though the accuracy is something like 99.999999%. You can ID the mother with 100% accuracy though.

Answer 2

Hello @windycity24 !

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Answer 3

hmm... Let me say it as, They are designed to predict the probability of some outcome. In relation to punnette squares, it's a good way of understanding how biologist (geneticists) can predict the likelihood of inheriting particular traits. This also gives parents the predicted frequency of all of the potential genotypes among the offspring each time reproduction occurs. Why? Because a parent might want to know the likelihood of a child bearing a certain genetically inherited disease such as cystic fibrosis.
I hope It Helps !
@Windycity24 What do you think ?

Answer 4

How will u find the paternity using a punnet square !
each and every male have the X chromosome

Answer 5

By using punnet square u can just follow an allele like X and Y but cannot differentiate the between individual X chromosomes

Answer 6

As @mrdoldum said u would need techniques like DNA profiling to do that

Answer 7

@Windycity24 @Abhisar @Koikkara

Let me elaborate on exactly why a punnett square is not valid and perfectly worthless for a paternity test. Punnett squares involve the pattern of inheritance of traits. I am sure you will agree there are many ways to get a trait, for eg, blue eyes (which is not a single gene/allele thing anyway). In any protein there are many places that mutations can occur that do not affect the expression of a trait. These locations, and similar locations that may not be in a coding region of the genome, are what should be used. This is because these types of mutations occur randomly and due to the neutral effect they have on fitness are passed down to the offspring. The randomness means that you can look at enough sites to be able to identify the person that donated the DNA with a high degree of reliability, 1/trillions or better.

Think of this kind of like phone numbers. If we only look at the last 4 digits of a phone number there are many people with those same 4 digits. If we look at all the numbers we find that each person has a unique number.

Answer 8

Another way of looking at: say there is a paragraph of text that you are interested in. If that is read to you, and the person pronounces all the words correctly, you will not now if the words were misspelled on the paper it was read from unless you actually look at the text itself.

In this analogy reading out loud is the visibility of a trait and looking at the text is equivalent to sequencing the gene that is responsible for the trait and seeing any minor mistakes in it.