Codominance - <span>A form of dominance in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive.
</span>Mutation<span> occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene.</span>
Air pollution; smoking in the house
<span>The question is asking "which includes the physical characteristics of an organism
Gene" and the answer is the phenotype. An organism's phenotype is basically its outward appearance and its phisical characteristics. In contrast, the other options, gene, allele and genotype, refer to the genetic make up of an organism - its genotype</span>
