IMAT 2019 Q29, confused by the wording

hello :slight_smile:

I cannot seem to understand, number 2. I thought the answer was both 1 & 2

An animal has a coat that has some patches of white hair and some patches of black hair. Cells
that make up a hair follicle form a single hair, which is either white or black.
Assume that there are no mutations following formation of the zygote.
A student wrote the following statements:
1 The cells in all the hair follicles contain the same genes.
2 The alleles in a hair follicle forming a white hair are different from the alleles in the
hair follicle forming a black hair.
3 Each white hair follicle cell contains two recessive alleles.
Which statement(s) is/are correct?

Correct answer =1

Alleles are one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location which in this case is for hair colour. So we know that the alleles for black hair and white hair are the same because the animal presents both white and black in the phenotype. Does this make sense?


Raya is correct, I would just add this question probably relates to operons, so the alleles in the genotype are the same in the whole organism, but environment has an effect on the phenotype (hair colour)


Yes exactly! Areas on the animal that get colder may have black patches and warmer areas white patches in order to adapt to the environment


Hi, thank you for your answers.I really appreciate it. I assumed this was referring to incomplete dominance. I am not sure how the cold is involved. Please can you correct me


Hi! So the phenotype is the result of BOTH genes and the environment while the genotype is affected by only genes. Does that make sense? They talk about the appearance of the animal so it’s the phenotype :slight_smile: My comment about white and black is irrelevant in this question but usually when the gene is the same, the environment can affect the phenotype


Yes thats true!

Just for extra info, this was an example of an operon system in Siamese cats, where the enzyme coded for by their genes normally works at lower temperatures and causes the hair to be black coloured. However, at body temperatures, the enzyme is denatured and cannot work to make the hair black, so they naturally become white. Alleles in each hair follicle cell are still the same though!


Thank you! This is a way better explanation:)


Thank you so much, makes a lot more sense. My last question, sorry for bothering, can a question based on dominance be asked similarly?

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No worries! Yes, there can sure be a question on complete dominance, incomplete dominance or codominance:)