Question

The expression of both alleles for a trait in a heterozygous individual illustrates?

1) co-dominance
2) polygenic inheritance
3) pleiotropy
4) incomplete dominance

Answer 1

Co-dominance is when both alleles for a trait are expressed equally in a heterozygous individual, as seen in the MN and ABO blood groups in humans.

Step-by-step explanation:

The expression of both alleles for a trait in a heterozygous individual illustrates co-dominance. In co-dominance, both alleles for the same characteristic are simultaneously expressed in the heterozygote.

An example of co-dominance is the MN blood groups in humans, where the M and N alleles are both expressed in heterozygotes (LMLN). Unlike incomplete dominance, where a heterozygote has an intermediate phenotype, in co-dominance, each allele's effect is equally observable in the phenotype.

ABO blood groups are another example of co-dominance. Individuals with blood type AB have both A and B antigens on the surface of their red blood cells, expressing both the A and B alleles equally. This is in contrast to incomplete dominance, like the snapdragon flowers, where offspring have a mixed phenotype rather than expressing both parental phenotypes.