Answer :
The scientist when bred pure red beetles with pure black beetles and the offspring's were all black this tells us that the black color is dominant over the red color in beetles.
Dominant alleles have an impact even if there is only one copy present in the individual.
Recessive alleles, also known as homozygous alleles, only manifest their effects in individuals who have two copies of the allele.
Since the red beetles are crossed with the black beetles and all offspring's are of black color this according to the law of dominance which states that In a heterozygote, one trait will mask the existence of another trait for the same characteristic, according to Mendel's law of dominance.
The dominant allele will be expressed solely, rather than both alleles contributing to a phenotype and hence the black color is dominant over red one.
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