Spinner x Normal

[asarg]

Hi,
So I have been told that a spinner (with the spider gene and the pinstripe gene) When crossed to a normal should yield:
25% Normal, 25% spider, 25% pinstripe, 25% spinner.
This is confusing me though, clearly there is something I don't understand because to me it seems as if you would get 50% spider and 50% pinstripe.
How is it that you can get normals and spinners out of this pair??
For example, how does the spinner pass both the spider and pinstripe gene to its offspring? And wont all offspring receive something from the spinner, and so normals wouldn't be possible because they would be masked by the dominant spider/pinstripe gene from the other parent.
Can someone explain this to me?
Thanks!

[LotsaBalls]

Each egg has a 50% chance of getting spider and pinstripe. If it gets neither then it will be a normal. A spinner is not a homozygous form it is a double heterozygous snake.

[asarg]

Okay, this makes sense, but I'm still not grasping it. How would I make a punnett square for a spinner x normal?
How should I represent the genotype of the spinner and how would i represent the genotype of the normal?

Thanks

[The Serpent Merchant]

Genetic Wizard 3.0 calculations by


Check out the part on Dihybrid crosses

http://en.wikipedia.org/wiki/Punnett_square

[sweballp]

I had a hard time grasping this aswell.

But I got it explained to me like this. (Waaaaaay simplified ofc)

Look at the genes at they were marbles in bags, each bag containing 2 marbles. A spinner for example have 1 spider marble and 1 normal marble in the "spiderbag" aswell as 1 pinstripe and 1 normal marble in the "pinstripebag".

When the offspring are formed they will randomly inherit 1 marble from each of the bags. That way the offspring may end up with both a spider and a pinstripe marble if you are lucky. But they may also end up with the normal marbles from each bag.

If we instead are talking about a superpastel (i.e. a homozygous animal), then both marbles in the "pastelbag" will be pastel. So it wont matter which marble gets picked out of the pastel bag, the offspring will inherit 1 pastel gene, and 1 only. So in this case all offspring will be pastel, no normals and no superpastels.

Hope this helped.

/E

[mattb]

Ya I find this confusing too sometimes but always something new to learn.

[Kinra]

According to WOB super pastel x super pastel will only produce supers

Genetic Wizard 3.0 calculations by

When bred together supers will only produce supers, but if you breed a super pastel to a normal you will ONLY get pastels.

[mattb]

When bred together supers will only produce supers, but if you breed a super pastel to a normal you will ONLY get pastels.

Yes I changed when I remembered the normal. Sorry.

[asarg]

Thanks for that analogy sweballp, It helped me make sense of it all, I was over simplifying the genetics and assuming the spinner only had spider and pinstripe genes (only one bag of marbles, containing spider and pinstripe), but the way i understand it now is that the spider and pinstripe genes are at different loci, (in different bags), and something is inherited from each loci (or bag of marbles). This made a lot of sense to me.

[h00blah]

I had a hard time grasping this aswell.

But I got it explained to me like this. (Waaaaaay simplified ofc)

Thanks for passing this knowledge on! This is a great way to look at it since most people will get lost when you're trying to explain the genetics using the bigger words

I gave you +rep for passing on such a simple way of explaining simple genetics