Answer:
Option A is correct
Step-by-step explanation:
Options for the questions are -
A) only the dominant allele is expressed when the both allele are inherited
B) only recessive allele is expressed when both allele are inherited
C) the recessive allele is expressed only if it moves to a different chromosome
D) the dominant allele can be expressed only if two homologous chromosomes have it
A dominant allele is the one which expresses its trait when present in pair either with another dominant allele or a recessive allele. While a recessive allele is able to express itself only when it occurs in pair with another recessive allele. Thus, option A is correct.
For instance if “R” represent the red dominant color of a flower and “r” represents recessive white color of flower, then RR and Rr represents the genotype of red flower while while color is expressed when the genotype of flower is homozygous recessive i.e rr
Hence, Option A is correct