Modifying a Sim's genes

Thursday 30 August 2007

Now that we have seen how genetic inheritance works in the game, you may want to change the genes of some of your existing Sims for the benefit of their future babies.

This article was supposed to be the last in the series, but when I get a chance to take some screenshots in SimPE, I will add a little bonus fourth.

Genetic inheritance in The Sims
Making custom content inheritable
Modifying a Sim’s genes
Updating a Sim’s genes after plastic surgery

What we’re trying to do here

If you’re changing your Sim’s DNA, it won’t change his appearance (except possibly for the skin color, as discussed below), so you would only do this if you plan for this Sim to have children in the future.

And remember, the genes are supposed to come from the Sim’s parents, in each case one from the father and one from the mother. If you already have some idea of what the parents looked like, then you should keep that in mind when you assign new genes. Pick one gene that you say comes from the father, and the other that comes from the mother, and try to keep it realistic in terms both of what the parents looked like and what the Sim looks like. A Sim can get a blond gene from a black-haired mother, but he can’t get a black-haired gene from a blond-haired mother, for example. And if he has black hair, he had better have a black hair gene in there somewhere. Unless realism is not your goal, in which case, have fun with the wacky genes.

Changing hair genes

As I mentioned in the first article, I am not really sure how the game works with “custom” hair colors—or even with correctly binned hair colors, for that matter—when it comes to inheritance. I don’t bother with those when I am changing the genes: since I change hairstyles so readily anyway as the babies grow up, I only care about what color hair they have. Therefore I only assign one of the four default colors.

Also, changing the genes for the hair will not affect the Sim’s appearance, just as changing his hair using a mirror will not affect his genes. For this reason, I don’t think it makes much difference whether a hair color is assigned as dominant or recessive: the game takes one of the two with 50% probability when deciding the hair color of the child. However, to be consistent with reality and with the game’s own system, if I am assigning one dominant gene (brown or black) and one recessive gene (blond or red), I always put the dominant gene into the dominant slot.

To change the hair color genes, first load the Sim’s DNA, as explained at the end of this post if you’ve forgotten how. The two values you may want to change are Dominant Hair and Recessive Hair.

In the example above, Yware has a custom hair gene from his father (and the Jeanette hair for males that I have is not color-binned), and the default black color from Matilda. Before Yware has children, I will want to change his dominant hair color gene to black.

So I will load his DNA, selct the value currently under Dominant Hair, and change it to the default value 00000001 – 0000-0000 – 0000-000000000000. Then click Commit, and then File—>Save.

Matilda’s father had brown hair, but her Sim was created in CAS so she only had black hair genes. I might decide that it would be more fun for Yware to have inherited a hidden brown gene from Matilda, and then I would change his recessive value to 00000002 – 0000-0000 – 0000-000000000000.

Just remember, kids, if you want to keep it realistic, and you have a blond or red-haired Sim, try not to sneak a black or brown gene into her DNA! (Unless she has been dyeing her hair for years and never told anyone…) Of course it won’t break anything, but her blond husband might be surprised if she has a black-haired baby, and I don’t think it will be a nice surprise.

for Black:
00000001 – 0000-0000 – 0000-000000000000
for Brown:
00000002 – 0000-0000 – 0000-000000000000
for Blond:
00000003 – 0000-0000 – 0000-000000000000
for Red:
00000004 – 0000-0000 – 0000-000000000000

Changing eye genes

Changing eye color genes is much like changing hair color genes. After a little testing with my amiable guinea pigs Eirik and Sigi, I am convinced that changing the eye color DNA does not change the eye color of the Sim. That can only be changed by modifying the Sim’s package file directly. Perhaps the game originally intended to allow you to change a Sim’s eye color using a mirror (colored contacts?) so the DNA had to be kept separate so the babies would still get the right color.

As explained in the first article in the series, eye color genetics is a little more complicated than simple dominant/recessive genes. If you have categorized your eyes according to the second article, it is up to you to remember how they were “rated” if you are concerned with realistic inheritance, e.g. two blue-eyed parents having a brown-eyed child. (Though eye color genetics are quite complicated in real-real life, so maybe that’s OK…)

The easiest way to assign eye color genes is to pick a Sim who already has the eye color you want and copy his value out of his DNA. Of course, if you have already changed his DNA, you will have to look up his expressed eye color in his package file. See the article about changing skin and eye colors for more info.

If you don’t have a Sim with that eye color but know what package file it is in (by filename), you can look in that same article for details on where to get the value that you should put into the “Eye” fields.

Here are the default eye colors, thanks to Choco!

for Brown:
32dee745-b6ce-419f-9e86-ae93802d2682
for Green:
51c4a750-c9f4-4cfe-801c-898efc360cb7
for Light Blue:
e43f33602-3a08-4755-8b83-a0d37a6c424b
for Dark Blue:
2d6839c5-0b7c-48a1-9c55-4bd9cc873b0f
for Gray:
0758508c-7111-40f9-b33b-706464626ac9
for Alien:
12d4f3e1-fdbe-4fe7-ace3-46dd9ff52b51

And remember to Commit before you Save!

Changing skin genes

Changing the skin genes is more problematic, because as we learned in “Change skin or eyes in SimPE”, the skin color of the Sim is actually determined by the dominant “Skintone” field in his DNA.

You are free to change his recessive skin color gene, however, and that is done in the same way as eyes and hair.

If you want to use one of the default skin colors, their values are:

for Very light:
00000001 – 0000-0000 – 0000-000000000000
for Light:
00000002 – 0000-0000 – 0000-000000000000
for Tan:
00000003 – 0000-0000 – 0000-000000000000
for Dark:
00000004 – 0000-0000 – 0000-000000000000

Otherwise you can get the skin color value either from an existing Sim with that color, or the package file directly using this method.

Appendix One – Loading the DNA

Load your neighborhood in SimPE (using Tools —> Neighborhood Browser). You might want to make a backup while you have the Neighborhood Browser open. Don’t say I didn’t warn you.
Once it has loaded, in the top left pane, select “Sim Description”.
In the top right pane, click on the “Type” bar at the top to sort by name. Then scroll down to find the Sim you want to modify, sorted by first name, and select him.
In the bottom pane, click on the “More” button and select “Open Sim DNA”. This will open a new tab with the Sim’s DNA selected. This tab is where you will change hair, eye, and skin genes.

Appendix Two – Shirtless Elf

I think we can all agree on this one. Also, you can see this crazy bug I have since I installed Pets & Seasons, where the wedding rings get skewed sidewise and slice through the finger. (But Sweetdew, Belsar, and this chapter are already worth it.)