1. Mitochondrial DNA is the small circular chromosome present inside the cell organelle called mitochondria used for energy production. This type of DNA passes from the mother to the offspring. Mitochondrial DNA (mtDNA) has several advantages over nuclear DNA (nDNA):
for species identification purposes
including a higher copy number
a lack of sequence ambiguities from heterozygous genotypes
a faster rate of mutation
Thus, the advantages of keeping some DNA needed by mitochondria in the cell’s nucleus and some in the mitochondria itself are given above.
2. The process of gene expression starts with the transcription of the genetic information in the DNA into genetic codes in the form of messenger RNA.
The messenger RNA then undergoes some processing such as modification of tails and removal of non-coding sequence before the genetic codes are translated to their respective amino acids in a process known as translation.
The amino acids are linked together by peptide bonds and the resulting primary protein structure is folded in specific ways depending on their functions.
3a. Disadvantages Mitosis
Some single cell organisms and some plants do not reproduce sexually through meiosis. Rather, they use mitosis only to make exact copies of their cells. The major disadvantage of this approach is that all of the organisms in a population or all of the plants in an area will have the exact same DNA. If a new disease comes along every single organism or plant will be wiped out because if one organism or plant is unable to fight the disease that means none can fight the disease.
Mitosis also does not produce any variation. So, a plant that reproduces through mitosis won't have the chance to produce offspring that might be better than the parent.
3b. Benefits of Meiosis
Meiosis continually reshuffles the genes resulting in a great variety of offspring. Without meiosis we would all look exactly alike. Meiosis allows each offspring to be different, and so potentially better, than the parent. If a disease comes along, there is a good chance that some of the population won't get sick or die because everyone's DNA isn't exactly alike.
An organism cannot reproduce all by itself, but must find another organism to reproduce. This takes more time and energy than simply being able to created a clone through mitosis.
