Question

Why is there no genetic dominance for traits in the mitochondrial genome?

a.) Mitochondrial mutations are always recessive.
b.) There is no diploidy in the mitochondrial genome.
c.) The dominant alleles were selected out of the population.
d.) There isn't enough mitochondrial DNA in each cell for any gene to dominate.

Answer 1

There is no genetic dominance in mitochondrial DNA because it is not diploid and is inherited only from the mother. With only one type of each gene present, there are no pairs for dominance to occur.

Step-by-step explanation:

The reason there is no genetic dominance for traits in the mitochondrial genome is because there is no diploidy in the mitochondrial genome. Unlike nuclear DNA, where each person inherits two sets of chromosomes, one from each parent, mitochondrial DNA (mtDNA) is inherited solely from the mother. This means that individuals only have one type of each mitochondrial gene, so there isn't a dominant or recessive allele at play in the same way it is in nuclear DNA. Furthermore, since mitochondria reproduce asexually and independently of the cell containing them, the process of genetic recombination that occurs during sexual reproduction—which can lead to dominant and recessive traits—does not take place within the mitochondrial genome.

Mitochondrial DNA mutates at a rapid rate, and this, along with its strictly maternal inheritance, makes mtDNA useful for evolutionary and genealogical studies. However, these mutations typically do not adhere to the traditional dominance model because the DNA in a mitochondrion isn't paired with DNA from another mitochondrion to interact in a dominant or recessive manner.