00:01My man Mandel loved to play with his P's. So cool science!
00:12What are dominant and recessive traits?
00:15Now that's a pretty wicked cool question, and today I'm going to show you a wicked cool genetics experiment
00:19you can do with me, right here, right now!
00:23And all you gotta do, quick, give me a thumbs up!
00:28Yeah, give me a thumbs up, it's not going to look as weird as you think giving your phone a
00:31thumbs up!
00:33When you give the thumbs up, is your thumb straight like mine, or does it bend all the way back?
00:38Let's say that your mom and your dad both have a straight thumb, like mine.
00:44Well, then you will also have a straight thumb, like mine.
00:50Let's say that your mom has a straight thumb, but your dad doesn't.
00:54Well, then you will have a straight thumb!
00:59Yeah, if you don't believe me, go check with your parents!
01:01Believe it or not, you will most likely have a straight thumb!
01:05I mean, there's a possibility you could have like a curved one, and you know, it is a possibility like
01:09a small chance,
01:09but you will most likely have a straight thumb!
01:15Now, with this one, I'm going to blow your mind!
01:18Let's say that both your mom and your dad both have curved thumbs!
01:23No matter what, there is always going to be a curved thumb!
01:30That's right, there's not even a slight chance that you will have a straight thumb!
01:35So, why is it that parents who both have curved thumbs could never have kids with straight thumbs?
01:42And, what does this have to do with dominant and recessive traits anyway?
01:46Well, don't look at me! Take a closer look at this!
01:52Before Mendel came along, people used to believe that organisms would combine their traits
01:57and offspring would be a mix of both parents, such as red mixing with yellow giving you orange.
02:02Gregor Mendel, living in a monastery as a monk back in 1856, noticed something interesting about plant generations.
02:09He did experiments from 1856 to 1863 with all sorts of plants in the monastery's massive garden.
02:16For example, in pea plants, he noticed that peas would appear green and yellow.
02:21He cross-pollinated two pea plants and noticed that the new generation of plants exhibited only traits from one parent
02:27plant,
02:28yellow peas, not a combination!
02:31He then cross-pollinated that generation and noticed in the third generation,
02:35the new pea plants exhibited traits of both the first and the second generation plants.
02:40He figured out that some genes must be dominant while other genes were recessive or hidden.
02:46To understand what's going on here, these experiments can be shown using what's known as a punit square.
02:51When genes combine, such as two dominant genes, the dominant trait will always appear.
02:56If a dominant gene combines with a recessive gene, then the dominant gene overrides the recessive and the dominant gene
03:02appears.
03:03However, if you get two recessive traits combining, a new trait will appear.
03:07A recessive trait, such as in Hitchhiker's Thumb.
03:10So now you know more about dominant and recessive traits.
03:14You know, being able to give me a thumbs up is why science is...
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