A male has black hair and a woman has white hair. What is the expected hair color of the offspring if both alleles are dominant?

[stunner5000pt]

Homework Statement

A male has black hair and a woman has white hair. What is the expected hair color of the offspring if both alleles are dominant?

Relevant Equations

Punnett squares

If we draw a punnet square, it would look like this

Male on horizontal Female on vertical	Cb	Cb
Cw	CbCw	CbCw
Cw	CbCw	CbCw

Does this mean that the offspring will have a blend of both black & white hair i.e. grey? Or is there something that is being missed here?

 

[Borek]

There is no information on what is the phenotype when there are two dominant alleles present.

Yes, I would expect some kind of gray looking hair, but whether it means every hair is gray, or half hair are black and half are white depends on the details of how the hair grows and where and how the genes fit in that mechanism (I have no idea). Could be you were given enough information separately, but if the question as worded is asked out of the blue (to keep with colors) there is no way to be sure.

 

[chemisttree]

It’s a trick question! White haired women are too old to have children!

Are the man and woman homozygous or heterozygous?

 

[pinball1970]

Homework Statement: A male has black hair and a woman has white hair. What is the expected hair color of the offspring if both alleles are dominant?
Relevant Equations: Punnett squares

If we draw a punnet square, it would look like this

Male on horizontal Female on vertical	Cb	Cb
Cw	CbCw	CbCw
Cw	CbCw	CbCw

Does this mean that the offspring will have a blend of both black & white hair i.e. grey? Or is there something that is being missed here?

Do you mean blonde? "White" has no pigment, aging reduces pigmentation over time as per the posts above.
Alternatively, albinism also has individuals with no to very little pigmentation. White hair.
I recall individuals are recessive so an albino will not produce offspring with white hair unless the partner is also albino or with the gene, heterozygous but phenotypically pigmented.

 

[Steve4Physics]

I'm asking this as a non-biologist. Does it make sense to say that both alleles (i.e. the black allele and the white allele) are dominant? Surely only one type of allele can be dominant - so the question is meaningless.

I'd be interested to know.

 

[pinball1970]

I'm asking this as a non-biologist. Does it make sense to say that both alleles (i.e. the black allele and the white allele) are dominant? Surely only one type of allele can be dominant - so the question is meaningless.

I'd be interested to know.

No you can have co dominance. Blood group AB for example

EDIT: A few nice examples here https://www.britannica.com/science/codominance

 

[Steve4Physics]

No you can have co dominance. Blood group AB for example

A few nice examples here https://www.britannica.com/science/codominance

Thanks. That's interesting. Your link says "Examples of codominance in animals include speckled chickens, which have alleles for both black and white feathers" which relates to the original question.

I suppose the original question should have said 'codominant' rather than 'dominant'.

 

[pinball1970]

Thanks. That's interesting. Your link says "Examples of codominance in animals include speckled chickens, which have alleles for both black and white feathers" which relates to the original question.

I suppose the original question should have said 'codominant' rather than 'dominant'.

I am still not sure what the OP means by "white," Blond, age/loss of pigment or Albino.

 

[Aurelius120]

Assuming it's a simple homework question,

Homework Statement: A male has black hair and a woman has white hair. What is the expected hair color of the offspring if both alleles are dominant?
Relevant Equations: Punnett squares

Does this mean that the offspring will have a blend of both black & white hair i.e. grey? Or is there something that is being missed here?

I think it will be black and white hair(no blending). Since the question says "both alleles are dominant", it implies they are codominant. In cases of codominance phenotypes don't blend unlike in incomplete dominance. I think this is a hypothetical question based on something like cattle coat colour.

 

[Algr]

I am still not sure what the OP means by "white," Blond, age/loss of pigment or Albino.

Given the context that this is about inherited genetics, it makes sense to assume that the woman is either blond, or a drow:

 

[jim mcnamara]

How about Poliosis?
example:
Poliosis conscripta - a white forelock usually seen in women
https://pubmed.ncbi.nlm.nih.gov/23850259/

I really think the issue is someone trying hard to post a question in English when it is not a first language.

 

[geekynerd]

this is a case of multiple allelism. if both the the allele is dominant codominance can be observed. (example: blood grouping).so both the allele can be expressed equally

 

[Laroxe]

The answer, like most things in genetics, is rather more complicated and issues like dominance may not be very helpful though the genes for dark hair are far more common across the globe. I am not convinced that continuing to teach the Mendelian single gene approach to genetics is useful, its misleading and causes all sorts of problems. We have to consider that people often carry genetic information that is not expressed in the phenotype, a reflection of our own genetic history. There are at least 21 different genes that can influence hair colour, and it's common for the colour to change over the lifespan. Hair colour is dependent on the production and mix of two different pigments and there are a number of genes that are involved in the production and these genes can be switched on or off in response to other factors. There are other factors that influence the quality of the colour and the distribution of the pigment that can also influence how the colour is perceived.

I thought the article from the family site provided a good description, and it has a useful chart. The Medline article is a bit more technical, surprisingly, the action of the various genes is still not well understood.

https://www.familyeducation.com/fam...y-genealogy/what-color-hair-will-my-baby-have
https://medlineplus.gov/genetics/understanding/traits/haircolor/

 

[BillTre]

The picture looks like an artistic creation (not real data).

Dominance is related to two alleles (alternate versions of the same gene) not comparisons with other genes at other genomic locations.

Epistasis between two different genes affects interactions between them.
An example might be in a biochemical pathway producing pigmentation. A gene inactivating an enzyme upstream of other enzymes/reactions is an example. The action of the inactive first enzyme in the pathway will block all production because the chemical needed to for subsequent reactions will not be present.