Polygenic Inheritance?

[GDT]

Hello folks,

I'm having a tough time understanding the difference between incomplete dominance and polygenic inheritance. When I search on the internet, I keep getting answers like incomplete dominance is a blending of traits, like with a red rose and a white rose becoming a pink rose. Whereas polygenic inheritance is more blending genes to produce skin color.

Now...to me these seem like the same things. You're blending genes together. From multiple things comes one thing that shares a blend of characteristics. What am I missing here?

Thanks!
GDT

 

[Cat_with_no_eyes]

I think dominance inheritance is when the more dominant colour for example a darker colour is more dominant, so that affects the outcome to be darker like itself. Incomplete dominance is blending so that would be a mix for example red and yellow produce orange.

Ya get my flow?

 

[Idle Mind]

Incomplete dominance is equal expression of the dominant and recessive alleles of a single gene, resulting in an intermediate phenotype.

Polygenic inheritance refers to situations where multiple genes have influence on phenotype.

 

[GDT]

Thanks for the answer! I get it now.

 

[GeoffP]

Damn, didn't even see this one. I'll add: in any polygenic system, you could have separate dominant and additive genes, additivity being the case where dominance = 0 and the heterozygote (Aa) being the phenotypic intermediate of the two homozygotes (AA and aa).

Example (means for weight in g):
AA Aa aa
60g 50g 40g

(Difference b/wn AA and aa: 20g. Additive substitution effect: 10g per "A" allele.)

I should mention on the quantitative scale that incomplete dominance can refer to those individuals not exactly intermediate in phenotype: so, in the above example of means of weight:

AA Aa aa
60g 55g 40g

would also be incomplete (I usually say partial) dominance without being exactly intermediate, which one calls "additive". (As in: A + A = 10g + 10g = 20g above the mean of the aa phenotype.)

Partial dominance can be positive (as in the above where the heterozygote approaches the high-phenotype homozygote (AA) or negative, if the Aa het had a mean of 45g, approaching the low-phenotype homozygote (aa).

 

[Mr MacGillivray]

what would weigh 50g then?

 

[GeoffP]

what would weigh 50g then?

A mouse, or perhaps your neural cortex.

 

[Mr MacGillivray]

That's a big assumption to make for a scientist. That someone from the general public has a neural cortex.

 

[GeoffP]

ENOUGH OF YOUR HUMAN TRICKERY! YOU WILL SUBMIT YOUR CORTEX TO THE DALEKS FOR EXPERIMENTATION!

...UHHHHH...I MEAN...I'M SURE YOU'RE OKAY...."DUUUDE". PLEASE REPORT WILLINGLY FOR EXPERIMENTATION.