Question

how does a protein differentiates a dominant and recessive gene. in case of incomplete dominance dominant is more expressed and recessive gene is less expressed , how does a protein know this much quantity of gene should be trancripted?

Answer 1

its a guess bit i think in this qn
the concept that in incomoplete dominance both the gene are dominant in equal amount and expresses itself in equal amount so it dosent matter for protein to see how much and of what it should transcript in how much amount it will transcript both genes in equal amount

Answer 2

The question of gene regulation (how much of a gene product should be made) has little to do with whether or not the gene is dominant or recessive.

How much is produced is determined mostly by cellular need, resulting in up and down regulation of particular transcription factors. Whether the allele is dominant or recessive has more to do with the nature of the protein product - whether, in the case of recessive alleles, it produces a non-functional protein, for example...

Answer 3

@heena in case of incomplete dominance both genes are not expressed equally

Answer 4

@blues your saying that amount of protein produced is determined by cellular needs ... but in some cases it wont.
consider the example of pigement expression in snapdragon . pigement expression is not dependent on cellular needs.
there both dominant and recessive genes are expressed in different proportion.
i want to know what is the reason for the expression of those genes in that proportion.

if its transcription factors then how does it selectively transcribes dominant than recessive in the above case of snapdragon

Answer 5

I think I might hazard a guess at a gene dosage effect here: only one allele is not enough for the full red colour of the homozygous plant flowers. The heterozygote has only one allele, the other being mutated and hence recessive. This might be the result of a promoter mutation and hence a lack of transcription factor binding but I'd guess at a truncation in the message as a result of an insertion,possibly of a transposable element.

Answer 6

@ebaxter though transposons have effect on gene expression in plants , i dont think that it is responsible for incomplete dominance in plants...

Answer 7

@chandhuru wel i tudyie that in cae of incomplete dominance both alelles occur eg- roan

Answer 8

To try and clarify what I meant in my previous answer I'll add this: the heterozygote produces half as much protein (and hence half as much of the red colour, known as anthocycanin) as the homozygote so the flowers are pink rather than red. Heena is quite right to draw your attention to Roan coat colour - this is another example of a heterozygote with a colour that is intermediate, although the coat is made up of regions of each colour. Have a look at Wikipedia under Roan (color) then lok at the genetics section of this page - it's pretty interesting.

Answer 9

@heena @ebaxter consider the case of snapdragon the gene for red colour is dominant over the gene for white colour.
In normal condition like in Pea plant only dominant gene codes for the protein .

my doubt is about the reason for the existence of incomplete dominance and difference in molecular mechanism of gene expression in dominant and incomplete dominance condition.