From observing the origin of the 2-bp deletion of the ND2 gene of the mtDNA from the paternal germ line, it is thought that this mutation occurred in embryogenesis and thus paternal leakage of the mtDNA was mainly exhibited during early stages of fertilization and embryo development (Schwartz & Vissing 2002).
Taking the theory of paternal mtDNA leakage during embryogenesis into account, the process of embryogenesis needs to be studied. Embryogenesis is the formation and development of embryos where after the egg is fertilized by the sperm, the sperm mitochondria enter the egg cell. Here in the egg is where the sperm mitochondria are outnumbered by the maternal mitochondria and are killed through a mechanism that identify the ubiquitin sperm are tagged with. Thus paternal mitochondria do not transmit to further cell stages of embryo development and mtDNA is solely believed to be maternal in inheritance. Taking the case study into account, the question that is raised is how paternal inheritance of mtDNA could have occurred if embryogenesis prevents it. Therefore, the further research in recombination of mtDNA can be conducted to see if mtDNA can be similar to nuclear DNA, where mtDNA can be incorporated or fused from many sources (Bromham et al 2002).
Investigating further into paternal inheritance of mtDNA observed in other mammalian species besides humans, studies were conducted on interspecific backcrosses of two mouse species, Mus spretus and Mus musculus. Three elements were addressed which included if the leaked paternal mtDNA in the fertilized eggs were going to display a stable distribution in all tissues once developed into adults, if the leaked paternal mtDNA was going to be transmitted to succeeding generations, and...
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... the presence of paternal mtDNA through allele-specific PCR assays (AS-PCR). The results exhibited 27 out of the 4092 offspring contained paternal mtDNA, therefore, displaying a paternal leakage frequency of 0.66%. The experimental methods were broken down into separate mating experiments (ME) where for ME1 DNA from 2046 offspring was isolated and screened for paternal inheritance through the AS-PCR1 technique. Six offspring from two separate matings contained paternal mtDNA leakage. From the six offspring, one contained heteroplasmy and another had an mtDNA turnover from maternal to paternal mtDNA. In order to confirm these results, a second screening of the offspring was preformed with AS-PCR2. For ME2, two mating pairs that were independent from one another presented mtDNA paternally. Two offspring pairs were observed to contain heteroplasmy (Wolff et al 2013).
Paabo’s team discovered an mtDNA sequence from a finger bone they found from around 40,000 years ago, as carbon dating is one of the most commonly used methods of determining a fossil’s age. (Hammer, 70). Also, Neanderthal mtDNA is differs severely from modern human mtDNA. For example, Microcephalin is a gene for brain size during the development of the organism.
Rienzo, Anna Di. Wilson, Allan. 1991. Branching pattern in the evolutionary tree for human mitochondrial DNA. Evolution 88: 1597-1601.
Recently mitochondrial transplants, mitochondrial donations, also referred to mitochondrial replacement has become a predominant topic in the medical community, chiefly in Canada, the United Kingdom, and the United States. Mitochondrial transplants would mean that couples who want to have a child, but the mother has defective mitochondrial deoxyribonucleic acid (mitochondrial DNA or mtDNA) could receive mitochondria from a donation. Therefore, the child would not be born with a mitochondrial disease. People who are diagnosed with mitochondrial disease have a life expectancy of nine months to fifty years, depending on when the person developed the disease. Both sides of this argument have valid opinions. Matt Ridley and Françoise Baylis wrote
Monotremes are mammals that are oviparous, or egg-laying. There are only 3 extant species of monotremes: the playtpus and two species of echidna. Their reproductive systems are highly specialized to facilitate both the production of eggs and milk. The male tract is quite simple. The female tract has qualities similar to those of birds, though female echidnas also possess pouches. The monotreme egg is also very specialized and somewhat similar to a reptile egg. Platypuses and echidnas have very different behaviors when it comes to mating, but their genetics are quite similar. Monotremes possess a few large chromosomes and several unpaired microchromosomes. The descendants of the first radiation of mammals, monotremes have characteristics of both placentals and marsupials, while still retaining characteristics of reptiles and birds in a combination all their own.
The exercise involved a series of ‘mating’ events resulting in 6 generations. Each mating event produced offspring with ‘possible’ newly inherited traits. The idea of ‘chance’ was included through simple coin tosses. Also, ideas of selection and mutations were introduced into the ‘gene pool’, which presented a deeper and more clear understanding of Mendelian inheritance and the Hardy-Weinberg equilibrium. Upon reaching the third generation, A B1 mutant allele was introduced to the blue locus-influencing fin shape and a G1 mutant allele was introduced to the green locus-influencing Mouth
From the ancient bones of the Neanderthals, scientists have been able to extract small amounts of DNA. The DNA comparisons to modern humans show no relationship, implying evolutionary separation (Kunzig, 159). Some anthropologists say the small sections of DNA found are not conclusive evidence, because modern humans show just as much variation in DNA. These people point out that individuals such as the “Portugal Kid” are hybrids of Neanderthals and modern humans, showing there was gene trading. One argument against this is that there is no skull from the ‘Portugal Kid” so it is hard to compare it to Neanderthals. Also, it is known that closely related species can breed and their offspring can be fertile, but they are still separate species (Kunzig, 161).
contains mitochondrial DNA (mtDNA), completely intact. Mitochondrial DNA is tougher than the DNA found in cell nuclei; it is also found in the cytoplasm of a fertilized egg and is passed only through maternal lineage. This makes it much easier for the team to study and makes testing more accurate. Paabo’s team, from Leipzig, Germany, used a method of amino acid content as a way of measuring extractible DNA from the bones. The amino acid method was a means for testing the DNA content in the fossils.... ...
The cell cycle is the synchronous process by which existing cells give rise to new cells. This process can be broadly divided into two stages: interphase and mitosis. During interphase, cells increase in size, replicate their chromosomes to form sister chromatids, and increase their rates of protein synthesis. During mitosis, sister chromatids are separated and transported to opposite cell poles, followed by cell division (cytokinesis). Recent investigations have revealed much information about the morphological changes that occur in mitotic cells. These morphological changes occur in a precise order and include, in chronological order, condensation of chromosomes, changes in microtubule assembly patterns, nuclear envelope breakdown, chromosome alignment at the center of the cell, chromosome separation to opposite cell poles, and nuclear envelope reassembly prior to cytokinesis. Similar morphological changes have been observed during meiosis, indicating that the processes driving DNA distribution in somatic cells and gametes is similar (Baserga, 1968).
Genes associated in Leigh’s Syndrome are involved in energy production in mitochondria (Leigh Syndrome.). The syndrome is known by the progressive loss of mental and movement abilities (Leigh Syndrome.). Leigh’s syndrome involves genetic mutations in mitochondrial DNA that interfere with energy sources that run cells in areas of the brain that play a role in motor movements (Leigh's Disease (Leigh's Syndrome)). Since Leigh’s Syndrome is a neurological disorder, it is characterized by the deterioration of the central nervous system (spinal cord, brain, etc.) (Leigh's Disease (Leigh's Syndrome)). The first signs of Leigh’s syndrome occur in infants: vomiting, diarrhea, and difficulty swallowing (Leigh Syndrome.). The symptoms, which rapidly progress, are caused by areas of damaged tissue (lesions) that develop in the brain (Leigh Syndrome.) In about 20-25% of people with Leigh’s syndrome it is inherited through mitochondrial pattern known as maternal inheritance (Leigh Syndrome.). Leigh’s Syndrome is inherited from the mother as a mutation found in mitochondrial DNA (mtDNA) (Leigh Syndrome | Disease). The mtDNA of the father is carried by sperm cells, but during fertilization it is lost. Therefore all of the mtDNA comes from the mother (Leigh Syndrome | Disease). A mother with Leigh’s disease will pass the traits to all of her children. However, only daughters will pass the mutation to the next generation (Leigh Syndrome | Disease). As children get older and the disease progresses, symptoms can include lack of muscle tone, generalized weakness, and episodes of lactic acidosis (Leigh's Disease (Leigh's Syndrome)). High levels of lactic acid in the brain and blood cause lactic acidosis (Leigh's Disease (Leigh's Syndrome)). Treatments for Leigh’s Syndrome include supportive therapies such as physical therapy and speech therapy (Leigh's Disease). To manage lactic
Common Summary: This study focuses on the evolution and of an organism’s genetics over time. In this study, Rebekah Rogers and Montgomery Slatkin from the University of California, Berkley compared the genetic sequences between two specimens of woolly mammoths, from two different environments and population sizes to test the genome evolution theory that small isolated populations of animals will cause an accumulation of detrimental genetic mutations and defects. To identify the shifts in the mammoth’s genetics, Rebekah et al. used ancient DNA sequences to identify the differences in heterozygous and hemizygous shifts in the DNA. Here the scientist were able to observe the deletions, retrogenes, premature stop codons, and point mutations that differed between the two mammoths. Through comparing SNPs, the scientist saw that the Wrangel mammoths had 318 genes with premature stop codons and that some of those stop codons affected the gene codes for the olfactory system and the structure of the odorant binding receptors that give mammals the ability to smell. Also through the comparisons, the scientists found that the Wrangel mammoth had 27,228 deletions compared to the 21,346 deletions in the mainland mammoths. The deletions in the Wrangel DNA effected 1628 bases that coded for synapse functions, urinary protein production, pheromones; and, the deletions on the FOXQI locus in the Wrangel mammoths caused the development of translucent hairs and a satin coat. These deletions had an increase of heterozygosity in the Wrangel mammoths and showed that there were defects in the mammal’s DNA repairing mechanisms. And by using genetic ontology, the results showed that the Wrangel mammoths had 1.3x as many retrogenes as the mainland mammoths. The increase of retrogenes included genes that affected transcription, translation, cell division, DNA repair, and the chaperones of protein
Mitochondria are organelles in cells that provide energy, and they have their own DNA. Sometimes, mitochondrial DNA has mutations in it, causing rare, deadly, and incurable diseases. Women who have defective mitochondria can pass these diseases onto their children, but mitochondrial replacement therapy allows these women to have healthy babies that are free from mitochondrial disease.
The idea of the project was to experiment breeding Drosophila Melanogaster (fruit fly) to figure out if certain genes of that species were sex linked or not (autosomal). A mono-hybrid cross and di-hybrid cross was performed. For the mono-hybrid cross, white eyed female and red eyed male were placed in one vial for them to reproduce. For the di-hybrid cross, red eyed and normal winged flies and sepia eyed and vestigial winged flies were placed in their vial to reproduce. In the mono-hybrid cross the results expected were within a 1:1:1:1 ratio. Expected results similar to the expected desired null hypothesis proposed with what the F1 parental generation breeds. The potential results would have had to have been within the ratios of 9:3:3:1. The results were clear and allowed the null hypothesis to be correct. The white eyed gene in the fruit flies is sex linked. Sepia eyes and vestigial wings are not sex linked and are examples of independent assortment.
Nachman, M W., W M. Brown, M Stoneking, and C F. Aquadro. "Nonneutral Mitochondrial DNA Variation in Humans and Chimpanzees." NCBI PubMed (1996). 30 Mar. 2008 .
The scientific and medical progress of DNA as been emense, from involving the identification of our genes that trigger major diseases or the creation and manufacture of drugs to treat these diseases. DNA has many significant uses to society, health and culture of today. One important area of DNA research is that used for genetic and medical research. Our abi...
To start this off, conception is the action of conceiving a child, and pregnancy is the period from conception to birth. They both share the same meaning: the process of getting pregnant. Conception happens when a sperm penetrates on one of the female’s eggs. Then, at around day 14 of a 28 day cycle, the egg leaves the ovary, and it is surrounded by a protective layer of cells. The fallopian tube is lined with cilia, which helps move the egg towards the womb. This is called ovulation. In the next 12-24 hours, the egg waits to be fertilized by a single sperm. The sperm then swims through the womb to meet the egg in the fallopian tube. And the sperm secretes enzymes to help penetrate the outer layer of the egg. Once the