00:01
Okay, we'll start with question four about the ability to taste ptc.
00:07
So we have capital t and little t, and the capital t is going to be the dominant one, and the ability to taste it is due to a dominant allele.
00:16
So let's start by writing these out.
00:18
So we've got t to taste it, we have little t for inability to taste it.
00:25
Now let's look for questions.
00:26
A, what is between the type of a non -taster? so this is someone who can't taste it, and because the ability to taste it is dominant, you only need one copy to be able to taste it.
00:39
So if you can't taste it, you have to be a heteroea homozygot.
00:44
So you have to be homozygous recessive, because if you have even one copy of the tasting allele, you'll be able to taste it.
00:53
So if we look at b, what are we doing the types of a taster? so they could have two copies.
00:58
They could be homozygous dominant, but they could also be a heterozygot, because in this case, the recessive one isn't noticed, because you only need one copy, be able to taste it.
01:13
And if we look at c, could a person with two tasters as parents have a non -taster, offspring? does this work? yeah, of course.
01:25
This is common in any case where you have dominance like this.
01:29
Imagine you have two people who are heterozygotes.
01:33
So both of them can taste ptc because they have at least one copy each.
01:38
And if they have a child, what are the options for the child's genotype? well, they could get both of the dominant, they could get one of each, or they could get both a b recessive.
01:49
And if they get both of a recessive, they won't be able to taste.
01:53
So it's entirely possible for a person with two tasters as parents to be a non -taster.
01:58
It just means those parents have to be heterozygotes.
02:02
Because imagine if just one of them were dominant homozygot, then the offspring choices would only be this, and you wouldn't be able to get a non -taster.
02:14
So that's question four.
02:17
So let's put you up here.
02:19
And let's go on to question five.
02:21
So we're looking at tomatoes now.
02:23
We have fuzzy skin and smooth skinned tomatoes.
02:27
So i'm going to put f is fuzzy.
02:30
F, it's smooth.
02:33
What is our question? so we have crossed a fuzzy skin tomato and a smooth skin tomato.
02:41
Right, so we need to determine the genotypes of the parents.
02:45
Well, let's look at the smooth skin tomato first, because this one is recessive...