00:01
We know that height is considered a polygenic factor.
00:03
It's one of those things that usually multiple genes play a role in determining how tall you're going to be.
00:08
So you might be just as tall as your mom, just as tall as your dad, or maybe somewhere in between, or like almost as tall as mom, something like that.
00:15
So we're looking at this scenario in plants where we're told these plants can be anywhere from 11 centimeters to 47 centimeters.
00:27
So it seems like 11 centimeters is the shortest, 47 is the tallest, and in that case there can be a difference of 36 possible centimeters.
00:40
Now in this question there's one piece of information that really helps us determine, you know, how many genes are at play and how much each gene influences plant height.
00:51
And that piece of information is that there are some plants that are 20 centimeters tall, and some plants that are 29 centimeters tall, meaning that those have to be some of the options for height.
01:12
So the way that i'm going to solve this is by taking this, taking the base number, the base height, and the difference, this 36 centimeters.
01:27
So like i know plants have a minimum height of 11 centimeters, but plants can also be 20 centimeters.
01:36
Well, there is a 9 centimeter difference from that, and there's a 9 centimeter difference from 20 to 29 centimeters tall.
01:47
So i'm going to take this 36 centimeters and divide it by 9, because it seems like the plants can grow in increments of 9 centimeters, and we get 4.
02:00
So the difference between the shortest height and the tallest height, there's 36 centimeters, which seem to be controlled by 4 alleles, which means we're looking at 2 different genes.
02:19
So when we look at the genotypes of the parents and offspring, we're starting with parents who are told one of them is the tallest height, they're 47 centimeters, and so that means that all 4 of their alleles are all dominant, because the more dominant alleles you have, the taller you're going to be.
02:42
But then the other parent who's only 11 centimeters, that's the shortest you can be, so they have no dominant alleles.
02:49
They are homozygous recessive.
02:52
So we can use that to figure out what we would expect in the f1 and then the f2 generation.
02:59
So the f1 is really easy.
03:01
We see that one parent can only give dominant a alleles, so no matter which one they get from that parent, they're going to get a dominant a.
03:10
The other parent can only give recessive, so all the offspring have to get a recessive from that parent...