Dihybrid Crosses & Punnett Squares

by Jason Amores Sumpter
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in this video, we're going to talk directly about die hybrid crosses in their pun, it squares. And so a die hybrid cross is really just cross fertilization between to die hybrid organisms and recall from our previous lesson video that die. Hybrid organisms are organisms that are hetero zegas for two specific genes. And so there is a very characteristic FINA typical ratio for die hybrid crosses that you should all be familiar with and that characteristic FINA typical ratio is 9 to 3 to three toe one. And so we'll be able to get some clarity on that once we get to our image down below. And so if we take a look at this image, notice that we're showing you over here a die hybrid cross crossing to die hybrid organisms. And so notice that parent number one is a dye hybrid organism because it's hetero zegas for two genes. It's hetero zegas for the shape jean here, and it's hetero zegas for the color jean here and also noticed that Parent number two is also die hybrid in the same way because it's hetero six. For these two genes and die, hybrid organisms have mawr possibilities when it comes to their game meats and so notice that they have mortgage a meets than what we've seen before in our other punnett squares. And these mawr possibilities, thes increased possibilities of game meats creates a larger, more complex punnett square. But it works in the same way as our previous punnett squares, where each box represents a possible fertilization event of the game. It's that you see aligned and so ultimately, when we take a look at the results of this die hybrid cross punnett Square, what you'll see is a very characteristic FINA tip IQ ratio, where there are nine ah, possibilities that have the dominant trait for both genes. So nine round and nine yellow, uh, Fina types. So nine dominant dominant FINA types. Then we have three dominant recess. If I've phenotype so three round green FINA types dominant recessive, then we have another three that are recess Ivo dominant So three wrinkled yellow FINA types and then we have one that is recessive recessive, one wrinkled green phenotype. And so this 9 to 3 to 3 to 1. FINA typical ratio is very characteristic of a die hybrid cross, and it's evidence to show that there is independent assortment that occurs. And so this here concludes our introduction to die hybrid crosses and their pundits squares and how they create this characteristic FINA typical ratio of 9 to 3 to 3 to 1 and will be ableto apply the concept that we've learned here as we move forward in our course. So I'll see you all in our next video.