Talk:Punnett square

How-to

Wikipedia is not a how to. That means that this article needs to be cleaned up so that is isn't a how-to. AndyZ 02:29, 7 January 2006 (UTC)

The section "Interpreting a punnet square" is really lol "how to make a punnet square" but it is valuable information and I don't think it should be deleted. Dr d12 20:01, 2 December 2006 (UTC)dr_d12

Agree with dr_d12 (72.141.120.45 22:34, 22 January 2007 (UTC))

Link recommendation

Perhaps there should be some pointer or classifcation to genetic theories, applications, or genetic mutation? Vandykee 23:55, 6 March 2007 (UTC) Punnett square solver online — Preceding unsigned comment added by 188.32.79.146 (talk) 14:58, 6 May 2016 (UTC)

"disfigured" alleles

I removed the following from "Situtations where punnet squares don't apply"

• a parent has a disfigured copy of the allele in question.

Does anyone know what this means? Tocharianne 03:25, 17 April 2007 (UTC)

It was vandalism added in the Revision of 22:04, 11 April 2007 by 24.199.66.233. - Dr d12 16:52, 17 April 2007 (UTC)

Semi-protection?

Nearly 100% of the recent edits on this article are IP vandalism and the reverting of IP vandalism. Would anyone object to semi-protection? I know we can keep reverting by hand, but it seems like a waste of effort on an article that remains rather static and is not being actively improved. EdJohnston (talk) 04:39, 8 April 2008 (UTC)

Wikipedia:WikiProject Genetics

There was a brief war of the bots; the project tag was added and removed. I just restored the tag, since we can all agree that this is a topic in Genetics. I also removed some old random stuff at the top of the page. EdJohnston (talk) 03:44, 15 May 2008 (UTC)

compare with Karnaugh map (or Veitch Diagram)?

Electrical engineers describe the Boolean algebra functions that crop up in digital logic designs using a diagram called a Karnaugh map which strikes me as being both structurally and functionally very similar to a Punnett square. Is it worth mentioning this correspondence anywhere? (Perhaps just a See Also link?) —Steve Summit (talk) 03:37, 30 June 2009 (UTC)

Abstract comparisons could be made, but I don't think K-maps are similar enough to Punnett squares to warrant mentioning in this article. While both tools are designed to show the possible combinations of multiple binary variables (0 and 1 states in K-maps, dominant and recessive alleles in Punnett squares), they don't have any other common features that I can think of off the top of my head. Their purposes seem very different, Punnett squares lack virtually all of of the operations critical to K-maps, and K-maps (notably) don't have to be be square. It's a neat point you bring up, but it just seems too peripheral to include. If you've got more rationale in favor of mentioning K-maps in this article, I'd be interested to hear it. Cheers, Emw2012 (talk) 04:32, 30 June 2009 (UTC)

How about a See also link then?

Umm.. is there any mathematics etc. links those 9:3:3:1 ratios? —Preceding unsigned comment added by 80.223.147.182 (talk) 07:31, 9 September 2009 (UTC)

A Veitch diagram, however, looks quite a bit like a Punnett square. If you represent a dominant allele as a zero, and a recessive allele as a one, you can find that by writing the products in each square, you can get the same output as a Punnett square. Another point reinforcing the notion that the Veitch diagram is like a Punnett square is that both the Punnett square and the Veitch diagram are required to be a 2x2 or larger square. 71.45.104.235 (talk) 23:03, 13 December 2013 (UTC)

I think it's K-Maps and Veitch diagrams aren't that related to Punnett square. First of all, Punnett squares are only useful for unlinked genes (e.g. ones on different chromosomes or are very distant on the same chromosome). Punnett Squares are just the first step to understanding genetics, which gets very complicated very quickly.

You could argue that these electronic boolean diagrams are similar if you treat Dominant Alleles as one and Recessive Alleles as zero, and treat the combination of two Alleles as a Boolean OR. I.e. AA genotype => A phenotype; Aa genotype => A phenotype; aa genotype => a phenotype. But that's about as far as you can take the analogy.

As visualization tools, they are similar and useful (as looking at a bunch of boolean algebra expressions is harder to understand.). I would add a "see also" link but not to drag electronics/boolean algebra into the fray.

Clemwang (talk) 21:58, 6 January 2021 (UTC)

Redundant rows in Punnett squares

A Punnett square helps determine the probability of different genotypic outcomes. If a parent is homozygous for a particular allele, it requires only one line. A good example is the Punnett at the top right of this article: there is no need of a second column, which only doubles the number of cells to count.

Maybe the problem comes from the convention of calling it a square. "Grid" might be better, but is more rarely used as a name.

I'd like to see the redundant column removed. As it stands, the diagram seems to be encouraging the unthinking perpetuation of this curious habit of redundancy. Dasyornis (talk) 07:59, 30 June 2010 (UTC)

Just because the cells happen to be equal for the Aa/aa test cross does not make them unnecessary. The math the chart represents is still identical to the Aa/Aa or any other case. There are still four outcomes, it just happens in this case that the outcomes are not all unique. I wouldn't collapse it down to one column as it may be confusing to the reader. Those familiar enough with probability to understand why the table could be drawn in one column in cases like these won't need to use a Punnet square to assist themselves in deriving the probabilities resulting in an independent cross between Aa and aa. --ThisIsPink (talk) 19:53, 11 January 2011 (UTC)

Banana Punnett Square Diagram

I am a new student to this, but the banana Punnett Square diagram seems incorrectly labeled. The quote says "A Punnett square showing a typical monohybrid cross", yet only one parent is heterozygous while the other parent is homozygous. By definition, a monohybrid cross involves two heterozygous parents. I apologize if I am understanding something incorrectly. Ramses89 (talk) 00:01, 1 September 2010 (UTC)

You're right. It is not a monohybrid cross, but a test cross. Dasyornis (talk) 03:32, 11 November 2010 (UTC)

I agree. Fixed. --ThisIsPink (talk) 19:53, 11 January 2011 (UTC)

Accuracy?

Has there been any research into the factual accuracy of the Punnett square? It seems to me that this is a good tool for making estimates, but it seems like it was based solely on observation. At this point in time, genetics has reached a level where we can probably decide if there is really a '75% chance' or if there are more factors at stakes. Anyone know more about it?168.158.220.3 (talk) 20:00, 21 November 2010 (UTC)

One thing that is missing from this article, is that Punnett Square is a simplistic view of genetics, albeit, a necessary first step. Prior to Mendel's work on the genetics of pea plants, people were very confused. They thought that genetic traits mixed, so that the reappearance of a recessive gene in later generations was very surprising. (Some traits are mixed, e.g. skin color.) Punnett Square is great at showing how unlinked dominant/recessive genes work. My biology professor speculated that if Mendel had presented his data with a Punnett Square (not yet invented), his work could have gained acceptance in his life time. Where Punnett Square breaks down, is when two genes are **linked** (i.e. are located on the same chromosome). Mendel, didn't know about chromosomes and didn't understand linked genes. When the genes are on separate chromosomes, then the two genes are unlinked and randomly distributed (assume other factors aren't taking place.). In fact, the genes that Mendel "happened" to study are on different chromosomes. (There is speculation he cherry picked which genes to study.) Another place where the Punnett Square "doesn't work" is with recessive lethal genes. Instead of getting a 1:2:1 ratio (homozygote dominant : heterozygote : homozygote recessive) , you get 1:2:0 (homozygote dominant : heterozygote : homozygote recessive dead)

George Box's quote is apt here: "All models are wrong, some are useful." IMHO, the article needs to be recast as the Punnett square being a great illustration of a simple, first model of genetics, but that in biology, things can get complicated as new discoveries are made.

See: https://www.ncbi.nlm.nih.gov/books/NBK21766/ An Introduction to Genetic Analysis, 7th edition where this is all explained. (There are some later editions, as biology is a rapidly changing field.)

Clemwang (talk) 17:44, 6 January 2021 (UTC)

A Punnet square still gives an accurate model of the probability of an individual inheriting any given alleles from their parents. How the traits are influenced by these alleles is a different story, and often aren't nearly as simple dominant/recessive. I suppose there is a possibility of a crossing over event within the gene, making a "hybrid allele", but in most cases the chances of that are negligible. CallmeNiel (talk) 00:17, 2 March 2011 (UTC)

In addition to Niel's comments, there can be breakdown in the outcomes of the Punnets squares in other circumstances as well. For instance if you were to cross Aa with Aa, normally you would expect 1/4AA, 1/2 Aa, 1/4aa. However, if having two recessive alleles leads to death of the child generation or improper development, you would not see these, so it would appear to be 1 part AA to two parts Aa. There are also assumptions of independence in the inheritance probabilities of the alleles - see Genetic_linkage. Newmanrs (talk) 02:21, 1 March 2012 (UTC)

Edit request from 97.76.235.46, 7 September 2011

When completing a simple Mendelian Punnett square, it is standard convention to not use "X" or "Y" - these letters should be reserved for representing sex chromosomes only - it can be confusing, especially when one goes further into using the Punnett square for sex-linked traits. Please consider changing the "Y"s to either an "A" or a "B", using the upper case for the dominant trait and the lower case for the recessive trait in the green and yellow diagram and the explanation. I have seen this problem in many diagrams where a well-intentioned individual picks "Y" to mean yellow. For teenagers it can be difficult to explain why it means yellow in one instance and in another it refers to a male. I am trying to speak out about this because it is a source of confusion. Additionally, the diagram that uses "B" is essentially correct except the maternal information goes on the left side, and the paternal across the top. The two-trait Punnett square is simarly flawed to the single trait as the "Y" should not be used there, either. Thank you for this consideration. 97.76.235.46 (talk) 21:08, 7 September 2011 (UTC)

Thanks for that! As far as I know paternal does go along the top where there is a preference. I'm not so sure about the "Y"s, but I'll see what I can do about editing the images. I've edited the table to use "a" in the meantime, but others may disagree. sonia♫ 06:21, 14 September 2011 (UTC)

For the lead image, I think the Y is okay there since there are some pretty strong redundant cues in the colour. For the other images, those Ys could be confusing. The tables should match the images so we'd want to change both. This image should be SVG, and once it is made into an SVG these changes will be straightforward. I don't know if paternal always goes across the top, conventionally, but that certainly seems common in the textbooks I've seen. Dcoetzee 09:25, 14 September 2011 (UTC)

Edit request on 31 March 2012

65.30.196.111 (talk) 14:48, 31 March 2012 (UTC) In this example, the allele for yellow seed color is dominant and the allele for green seed color is recessive. When the two alleles of a pair are different, one is dA gene can exist in more than one form? Organisms inherit two alleles for each trait. Dominant and the other are recessive. The principles that govern heredity were discovered by a monk named Greg or Mendel in the 1860's. One of these principles now called Mendel’s law of segregation, states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization. Organisms have two alleles for each trait. When the alleles of a pair are heterozygous, one is dominant and the other is recessive. The dominant allele is expressed and the recessive allele is masked. Mendel crossed true-breeding plants that differed for a given character A monohybrid cross involves one (mono) character and different (hybrid) traits. Pollen from true-breeding pea plants with purple flowers (one trait) was placed on stigmas of true-breeding plants with white flowers (another trait). The F1 seeds were all purple; the white flower trait failed to appear at all. Because the purple flower trait completely masks the white flower trait when true-breeding plants are crossed, the purple flower trait is called dominant, and the white flower trait is called recessive. The F1 plants were allowed to self-pollinate. This step was the monohybrid cross. (or the F1 cross). The progeny, called F2, were examined: roughly 1/4 were white, and 3/4 were purple. Mendel proposed that the units responsible for inheritance were discrete particles - particulate theory

Not done: please be more specific about what needs to be changed. I see a lot of text here, but no proposal for a change to the article. Can you be more specific? Thanks!   — Jess· Δ♥ 15:24, 31 March 2012 (UTC)

Edit request on 24 February 2013

I want to add in this page the translation of this page in the Portuguese Wikipedia: pt:Quadro de Punnett Caioponce (talk) 17:29, 24 February 2013 (UTC)

Done. Thank you, Fvasconcellos (t·c) 18:15, 24 February 2013 (UTC)

More Punnett Square pictures

I've made a set of Punnett squares.

A Punnett Square showing a BB x BB cross for eye colour.

A Punnett Square showing a BB x Bb cross for eye colour.

A Punnett Square showing a BB x bb cross for eye colour.

A Punnett Square showing a Bb x Bb cross for eye colour.

A Punnett Square showing a Bb x bb cross for eye colour.

A Punnett Square showing a bb x bb cross for eye colour.

Feel free to include them wherever appropriate. dllu(t,c) 18:43, 5 March 2013 (UTC)

What is dominant over what?

From the sidebar: "(yellow is the dominant color over green for pea pods, in contrast to pea seeds where yellow is dominant over green)" ... What? 217.64.163.97 (talk) 06:57, 8 May 2020 (UTC)