mitochondrial DNA

Examples of mitochondrial DNA in the following topics:

• Endosymbiotic Theory and the Evolution of Eukaryotes

  • Nuclear and mitochondrial DNA are thought to be of different (separate) evolutionary origin, with the mitochondrial DNA being derived from the circular genomes of bacteria that were engulfed by ancient prokaryotic cells.
  • Mitochondrial DNA can be regarded as the smallest chromosome.
  • Interestingly enough, mitochondrial DNA is inherited only from the mother.
  • The mitochondrial DNA degrades in sperm when the sperm degrades in the fertilized egg or, in other instances, when the mitochondria located in the flagellum of the sperm fails to enter the egg.
  • Some bacteria have the DNA enclosed by two membranes; however, there is no evidence of a nucleolus or nuclear pores.

• Characteristics of Eukaryotic DNA

  • Eukaryotic DNA is packed into bundles of chromosomes, each consisting of a linear DNA molecule coiled around basic (alkaline) proteins called histones, which wind the DNA into a more compact form.
  • A major DNA difference between eukaryotes and prokaryotes is the presence of mitochondrial DNA (mtDNA) in eukaryotes.
  • Because eukaryotes have mitochondria and prokaryotes do not, eukaryotic cells contain mitochondrial DNA in addition to DNA contained in the nucleus and ribosomes.
  • The mtDNA is composed of significantly fewer base pairs than nuclear DNA and encodes only a few dozen genes, depending on the organism.
  • Eukaryotic DNA is stored in a nucleus, whereas prokaryotic DNA is in the cytoplasm in the form of a nucleoid.

• Microbes and the Origin of Life on Earth

  • They have their own DNA, which is separate from the DNA found in the nucleus of the cell.
  • And both organelles use their DNA to produce many proteins and enzymes required for their function.
  • Mitochondrial DNA (mtDNA) has a unique pattern of inheritance.
  • Because of its unique characteristics, mtDNA has provided important clues about evolutionary history.
  • For example, differences in mtDNA are examined to estimate how closely related one species is to another.

• Components of Blood

  • Mature RBCs lack a nucleus and organelles and have no nuclear DNA.
  • They lack hemoglobin but contain organelles, a nucleus, and nuclear DNA.
  • Platelets contain mitochondrial DNA, but not nuclear DNA.

• Platelets

  • Because they lack a nucleus, they do not contain nuclear DNA.
  • However, they do contain mitochondria and mitochondrial DNA, as well as endoplasmic reticulum fragments and granules from the megakaryocyte parent cells.

• Measuring Biodiversity

  • Technology has matured to the point where we can begin cataloging the planet's species in accessible ways; DNA barcoding is one such method.
  • DNA barcoding is one molecular genetic method, which takes advantage of the rapid evolution in a mitochondrial gene present in eukaryotes, to identify species using the sequence of portions of the gene.
  • DNA barcoding is a taxonomic method that uses a short genetic marker in an organism's DNA to identify it as belonging to a particular species.
  • The most commonly-used barcode region for animals, at least, is a segment of approximately 600 base pairs of the mitochondrial gene cytochrome oxidase I (COI).
  • These now can be identified with DNA barcoding.

• Predicting Disease Risk at the Individual Level

  • The introduction of DNA sequencing and whole genome sequencing projects, particularly the Human Genome project, has expanded the applicability of DNA sequence information.
  • Genomics is now being used in a wide variety of fields, such as metagenomics, pharmacogenomics, and mitochondrial genomics.

• Mitochondria

  • Mitochondria are double-membraned organelles that contain their own ribosomes and DNA.
  • The mitochondrial inner membrane is extensive and involves substantial infoldings called cristae that resemble the textured, outer surface of alpha-proteobacteria.
  • Mitochondria have their own (usually) circular DNA chromosome that is stabilized by attachments to the inner membrane and carries genes similar to genes expressed by alpha-proteobacteria.
  • The space between the two membranes is called the intermembrane space, and the space inside the inner membrane is called the mitochondrial matrix.

• The Evolution of Mitochondria

  • The mitochondrial inner membrane involves substantial infoldings called cristae that resemble the textured, outer surface of alpha-proteobacteria .
  • Mitochondria have their own circular DNA chromosome that is stabilized by attachments to the inner membrane and carries genes similar to genes expressed by alpha-proteobacteria.
  • One possible explanation for mitochondria retaining control over some genes is that it may be difficult to transport hydrophobic proteins across the mitochondrial membrane as well as ensure that they are shipped to the correct location, which suggests that these proteins must be produced within the mitochondria.
  • A third possible explanation is that mitochondria need to produce their own genetic material so as to ensure metabolic control in eukaryotic cells, which indicates that mtDNA directly influences the respiratory chain and the reduction/oxidation processes of the mitochondria.
  • In this transmission electron micrograph of mitochondria in a mammalian lung cell, the cristae, infoldings of the mitochondrial inner membrane, can be seen in cross-section.

• Nucleic Acid Sequencing and rRNA Analysis

  • The genes coding for it are referred to as 16S rDNA, and are used in reconstructing phylogenies.
  • In addition, mitochondrial and chloroplastic rRNA are also amplified.
  • Principal limits are the lack of real universal primers; DNA amplification biases and reference database selection impact the annotation of reads.