Final answer:
A merodiploid is a haploid organism that contains a second copy of a part of its genome, which differs from polyploidy, where an individual has more than two complete sets of chromosomes. Merodiploidy is particularly common in bacteria due to plasmids carrying additional gene copies.
Step-by-step explanation:
A merodiploid is an organism that contains a second copy of a part of its genome within a haploid cell. In other words, it is a haploid organism that has additional copies of some genes, therefore only part of the haploid genome is duplicated. This contrasts with a complete duplication of the entire genome, as seen in a polyploid organism, where more than two sets of chromosomes are present. A merodiploid situation can be common in bacteria, where it refers to a bacterial cell that has two copies of a particular gene or genes, usually as a result of the presence of an extrachromosomal fragment, such as a plasmid, that carries a copy of the gene in addition to the one present on the chromosome.
Merodiploidy differs from conditions such as polyploidy, which is where an organism has more than two complete sets of chromosomes, commonly seen in plants and rare in animals like some species of fish and amphibians. Diploid organisms, like most plants and animals, contain two copies of each chromosome, one from each parent, creating a full set for their species. In contrast, a merodiploid organism only has additional copies of some, but not all, genes.