13. Mendelian Genetics
Punnett Square Probability
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In this video, we're going to begin our lesson on Punnett Square probability or probabilities that relate to Punnett squares. Now throughout this lesson, we're going to relate the probability of coin flips to the probabilities of Punnett squares. And the reason that we can relate the probability of coin flips to the probabilities of Punnett squares is because they are representing independent events. And so 2 events are independent of one another if the outcome of one event does not affect the outcome of the other event. For example, the outcome of 1 coin flip does not impact or affect the outcome of second coin flip. Just like the outcome of 1 fertilization event does not impact or affect the outcome of another fertilization event. And so that's why again the probability of coin flips can be related to the probabilities opponent squares. Now moving forward throughout this lesson we're going to introduce and explain 2 different rules when it comes to the probabilities of punnett squares. And the first rule is going to be the rule of multiplication, whereas the second rule that we're going to introduce is the rule of addition. Now the rule of multiplication or the rule of addition can be used to determine probabilities and to predict genetic crosses. And again, we'll explain and introduce these rules as we move forward in our course in their own separate videos. But for now, notice down below what we're showing you are independent events of these coin flips, of these 2 coin flips. And so notice over here we're showing you coin flip number 1, and coin flip number 1 has a 50% probability of landing on heads and another 50% probability of landing on tails. And so again 50% is the same as 1 half. And then over here what we're showing you is coin flip number 2, and coin flip number 2 is an independent event from coin flip number 1 because the outcome of coin flip number 1 does not impact or affect the outcome of coin flip number 2. And so when we flip coin number 2, there's still a 50% probability that it will land on heads and a 50% probability that it will land on tails. And so you can imagine that these coins here represent alleles, and so when you do that you can use the coins to generate a punnet square as we can see here. And so you can see, that this square here is representing the possibility of both coins landing on heads. This one is representing the possibility of 1 landing on heads, 1 landing on tails. This one's the probability of landing 1 on tails, 1 on heads. And this one's the probability of both of them landing on tails. And so again, we are going to be relating the probability of coin flips to the probabilities of punnett squares as we move along through this lesson. And so this here concludes our introduction to punnett square probabilities. And again, in our next lesson video we're going to introduce and explain the rule of multiplication. So I'll see you all in that video.
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