The Ultimate Sims Genetics Tutorial! Chapter 1
Ambitious title, huh? Well, this is an ambitious tutorial. Basically, I'm going to be compiling all the information I've absorbed by obsessively reading and observing. (A lot of the basics, when it comes to the in-game number crunchy stuff, comes from various threads at MATY and MTS2.) I hope to explain how sims genetics works, what options you have for controlling genetics in your game, and how to modify the custom content you make or download so it behaves the way you want it to.
Table of Contents
1. Introduction to Genetics
2. How Genetics Works in The Sims 2
3. Default Replacements vs. Custom Content
4. Modifying Custom Hair
5. Modifying Custom Eyes
6. Modifying Custom Skintones
7. Making a REALLY Custom Game
N.B.: I am tagging these for reference, and feel free to link people here. This is mainly being written so I can link people here and not rewrite the same information out repeatedly. :)
First of all, I'm aware most of the people who will read this have some sort of basic education in the concept of genetics and inheritance. However, some teachers teach it half-assed, or you might have been out of school awhile, so if you're trying to remember how this sort of thing works, start here!
What sort of authority do I have in this? I have a B.S. in Biology with a focus on Ecology and Evolution, and I'm licensed to teach Biology on the secondary level. So I HAVE taught this lesson before! :D Let's go.
Genes and Alleles
All living things have information encoded in their DNA. We call the piece of DNA that refers to a specific trait a gene. In organisms that reproduce sexually, they receive DNA from both parents. So, in most cases, the offspring receives two copies of a gene for a trait: one from each parent. Each copy is called an allele.
Dominance
Some copies of genes suppress other copies. This is called dominance.
A basic textbook example of dominance is the trait in humans for tongue-rolling. Some people can roll their tongue (curling up each side til they touch) and some people can't. However, have you ever noticed when this comes up that most people can do it? That's because the allele for tongue-rolling is dominant and the allele for NOT tongue-rolling is recessive.
As long as you have at least one copy of the allele for tongue-rolling, you can do it. It doesn't matter what your other allele is.
For those of you who are a little more visual, I made a diagram. Plus, this lets me introduce the way I'll be notating alleles and crosses for the rest of the tutorial. If I use a capital letter to represent an allele, then it is dominant. A lowercase letter indicates that it's recessive. Finally, the traits are colored for a reason--the background color of the box indicates the allele that will be expressed.
So this diagram shows the various combinations of genes for the tongue-rolling trait. As you can see, any person with ONE allele FOR tongue-rolling will be able to do it.
A person with two dominant alleles will always pass a dominant allele on to their offspring. A person with two recessive alleles will always pass a recessive allele on. A person with one of each has a 50/50 shot for each type, because half of their sex cells carry one allele and the other half, the other. So people with one recessive allele are still important to carrying on that recessive trait...since they carry a recessive allele, they're called carriers.
If we know what alleles the parents have, we can predict what traits their children will express. We can make a diagram called a cross or a Punnett Square to help us visualize.
For instance, one parent with two dominant tongue-roller alleles (TT) plus a parent with two recessive non-tongue-roller alleles (tt) gives us this cross:
Every kid is going to have one of each allele. This gives us all tongue-rollers carrying an allele for non-tongue rolling.
So let's say one of these kids (Tt) ends up with another person with two recessive non-tongue-roller alleles (tt):
Half of the kids (now remember, we're talking statistically) will end up with a dominant allele from one parent, and a recessive from the other. The other half will get a recessive gene from each parent.
In most cases, genes for human traits are a bit more complicated than one set of dominant/recessive alleles. Sometimes two alleles together cause a different effect rather than one simply being dominant. Sometimes you have multiple alleles determining how a trait is expressed. Sometimes, a trait ends up being on a sex chromosome, so rules of inheritance are different for males and females. This is why a good textbook example doesn't mention traits like hair or eye color in humans--the rules of inheritance for these traits are more complicated that even the scope of a college Intro Genetics course.
As we will see, even sims' genetics aren't quite this simple. However, without knowing the basics, you can't make heads or tails of it.
Chapter 2: How Genetics Works in The Sims 2
Table of Contents
1. Introduction to Genetics
2. How Genetics Works in The Sims 2
3. Default Replacements vs. Custom Content
4. Modifying Custom Hair
5. Modifying Custom Eyes
6. Modifying Custom Skintones
7. Making a REALLY Custom Game
N.B.: I am tagging these for reference, and feel free to link people here. This is mainly being written so I can link people here and not rewrite the same information out repeatedly. :)
First of all, I'm aware most of the people who will read this have some sort of basic education in the concept of genetics and inheritance. However, some teachers teach it half-assed, or you might have been out of school awhile, so if you're trying to remember how this sort of thing works, start here!
What sort of authority do I have in this? I have a B.S. in Biology with a focus on Ecology and Evolution, and I'm licensed to teach Biology on the secondary level. So I HAVE taught this lesson before! :D Let's go.
Genes and Alleles
All living things have information encoded in their DNA. We call the piece of DNA that refers to a specific trait a gene. In organisms that reproduce sexually, they receive DNA from both parents. So, in most cases, the offspring receives two copies of a gene for a trait: one from each parent. Each copy is called an allele.
Dominance
Some copies of genes suppress other copies. This is called dominance.
A basic textbook example of dominance is the trait in humans for tongue-rolling. Some people can roll their tongue (curling up each side til they touch) and some people can't. However, have you ever noticed when this comes up that most people can do it? That's because the allele for tongue-rolling is dominant and the allele for NOT tongue-rolling is recessive.
As long as you have at least one copy of the allele for tongue-rolling, you can do it. It doesn't matter what your other allele is.
For those of you who are a little more visual, I made a diagram. Plus, this lets me introduce the way I'll be notating alleles and crosses for the rest of the tutorial. If I use a capital letter to represent an allele, then it is dominant. A lowercase letter indicates that it's recessive. Finally, the traits are colored for a reason--the background color of the box indicates the allele that will be expressed.
So this diagram shows the various combinations of genes for the tongue-rolling trait. As you can see, any person with ONE allele FOR tongue-rolling will be able to do it.
A person with two dominant alleles will always pass a dominant allele on to their offspring. A person with two recessive alleles will always pass a recessive allele on. A person with one of each has a 50/50 shot for each type, because half of their sex cells carry one allele and the other half, the other. So people with one recessive allele are still important to carrying on that recessive trait...since they carry a recessive allele, they're called carriers.
If we know what alleles the parents have, we can predict what traits their children will express. We can make a diagram called a cross or a Punnett Square to help us visualize.
For instance, one parent with two dominant tongue-roller alleles (TT) plus a parent with two recessive non-tongue-roller alleles (tt) gives us this cross:
Every kid is going to have one of each allele. This gives us all tongue-rollers carrying an allele for non-tongue rolling.
So let's say one of these kids (Tt) ends up with another person with two recessive non-tongue-roller alleles (tt):
Half of the kids (now remember, we're talking statistically) will end up with a dominant allele from one parent, and a recessive from the other. The other half will get a recessive gene from each parent.
In most cases, genes for human traits are a bit more complicated than one set of dominant/recessive alleles. Sometimes two alleles together cause a different effect rather than one simply being dominant. Sometimes you have multiple alleles determining how a trait is expressed. Sometimes, a trait ends up being on a sex chromosome, so rules of inheritance are different for males and females. This is why a good textbook example doesn't mention traits like hair or eye color in humans--the rules of inheritance for these traits are more complicated that even the scope of a college Intro Genetics course.
As we will see, even sims' genetics aren't quite this simple. However, without knowing the basics, you can't make heads or tails of it.
Chapter 2: How Genetics Works in The Sims 2