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Why do co-dominant alleles NOT produce simple Mendelian ratios? (A) Both alleles are expressed in the phenotype - HSC - SSCE Biology - Question 10 - 2014 - Paper 1
Question 10
Why do co-dominant alleles NOT produce simple Mendelian ratios? (A) Both alleles are expressed in the phenotype. (B) Neither allele is expressed in the phenotype. ... show full transcript
Worked Solution & Example Answer:Why do co-dominant alleles NOT produce simple Mendelian ratios? (A) Both alleles are expressed in the phenotype - HSC - SSCE Biology - Question 10 - 2014 - Paper 1
Step 1
A) Both alleles are expressed in the phenotype.
Answer
This option correctly identifies that in co-dominance, both alleles are expressed equally in the phenotype of the heterozygote. For instance, in the case of blood type in humans, alleles A and B are co-dominant, and individuals with both alleles display type AB blood.
Step 2
Step 3
C) The recessive allele is only expressed in the homozygous genotype.
Answer
This statement is generally true for simple Mendelian inheritance but does not apply to co-dominance. In co-dominance, both alleles are expressed even in heterozygous conditions, thus making this option irrelevant.
Step 4
D) The expression of the dominant allele is affected by the recessive allele.
Answer
This is not accurate in the context of co-dominance. In co-dominance, the expression of each allele is independent, meaning they do not influence each other’s expression. This characteristic is what differentiates co-dominance from typical dominant-recessive relationships.