The genetics article by Monte Morin of the Los Angeles Times seeks to expound some studies conducted on how DNA tests have proven reliable in the discovery of fetal disorders on fetus. The article has basically argued that accurate screening of expectant mothers can be used in identification of possible cases of genetic disorders that have been caused by excess chromosomes. DNA testing is one of the fastest, safest and most precise methods of screening pregnant mothers for chronic abnormalities such as Down syndrome. This method of testing has been adopted in different regions as standard for prenatal care. The importance of verifying the DNA method majorly emanated from the argument of some experts who complained that it is not scientifically proven.
The DNA testing has proven more effective than the non-invasive methods of screening such as ultrasound examinations. It involves what the author called parallel sequencing technology. The article posited that Down syndrome, like several other trisomies, is created when one fetus has trio copies a given chromosome as opposed to the normal two. It employs a test called Illumina test, which involves counting the number of DNA fragments associated with a specific disorder. In a situation where the fragments exceed the average number for a normal blood sample, one is warned of possible disorder on the infant, thus required to undertake a more conclusive diagnostic test.
Using an ultrasound scanner, a physician can use a hypodermic needle in drawing some fluid from the uterus, which is used for the DNA testing. This method has been approved by various authorities in study of genetics as effective and reliable for mothers who wish to be sure about their unborn children’s health.
Monte, M. (2014, February 26). Study calls DNA test reliable in discovering fetal disorders. Los Angeles Times. Retrieved from http://articles.latimes.com/2014/feb/26/science/la-sci-fetal-dna-test-20140227
Estrogen Metabolite Ratios – A Naturopathic Perspective
Over the years, scientists have conducted extensive research on the causative agents of cancer. One such research set out to find the causative agents of breast cancer. From research, estrogen compounds have been associated with breast cancer. The two key determinants have been found to be 2- hydroxyesterone and 16α-hydroxyestrone. It was found that 2- hydroxyesterone was a beneficial compound in the body as its high percentage in the breast lowers the prevalence of breast cancer while 16α-hydroxyestrone was found to be non- beneficial. High amounts of 16α-hydroxyestrone were found to be the main factor in influencing breast cancer.
This theory of percentages of 2- hydroxyesterone and 16α-hydroxyestrone has been supported over years. According to the theory, all women have these two compounds and what differ are their percentages in the body. If one has high percentage of 2- hydroxyesterone than 16α-hydroxyestrone then she is at a lower risk of suffering from breast cancer. On the other hand, if one has high percentage of 16α-hydroxyestrone compounds in the breast than 2- hydroxyesterone, then she is in a very high risk of suffering from breast cancer.
In recent years, other researchers have countered the theory. They have found out that the theory was not based on statistical facts rather, very few scientists paid attention on the significance of statistical analysis. A lot of effort has since then been put on the research to determine whether estrogen metabolites are determinants of breast cancer or not. In one of the researches, it was found that the percentage of the two metabolites only applied to women who had not reached their menopause. That is those who feared the risk of breast cancer were those with high percentages of 16α-hydroxyestrone than 2- hydroxyesterone but this was the case only to a limited number of women- those below their menopause age.
In another research, determination of percentages of the two estrogen metabolites, and their effect to breast cancer, it was found that in the selected group of women, no significant difference was ascertained. Women with high ratios of 2- hydroxyesterone and those with 16α-hydroxyestrone had no difference all the same. This research again disapproves the initial theory of estrogen metabolites being key determinants of breast cancer. In a few researches however, there were found a relationship between the estrogen metabolites and breast cancer.
In most cases in the research findings, 2- hydroxyesterone and 16α-hydroxyestrone do not have any influence as to whether one will suffer from breast cancer neither do their percentages in the one’s body control cancer for those already suffering from breast cancer. This again contradicts the theory, which has been embraced and appreciated by many medics over years (Schor 1).
A lot of research and significant data has been done to disapprove the theory of2- hydroxyesterone and 16α-hydroxyestrone in controlling or reducing breast cancer. For instance one researcher, gave breast cancer patients a diet rich in flaxseed which increases 16α-hydroxyestrone which according to the estrogen metabolite theory is harmful but results indicated that the consumption of flaxseed did not influence the risk of cancer. It is therefore evident from recent research that the theory of estrogen metabolite is not true (Schor 1).
Scientist, researchers and medics should therefore embrace and appreciate the facts from recent research findings. There is no type of estrogen compound in the body should be referred to as beneficial or not beneficial and so medics should not recommend dietary restrictions on patients based on whether the foods or supplements are rich in the metabolites.
Opinion from reference
Consumption of flaxseed as a supplement, which increases levels of 16α-hydroxyestrone, has been found not to have any influence in controlling risks of breast cancer in women who have reached their menopause. Medics should not recommend dietary restrictions on patients based on whether the foods or supplements are rich in the estrogen metabolites.
Schor, Jacob. “Estrogen Metabolite Ratios.” Naturopathic Doctor News & Reviews. 2014. Web. http://www.ndnr.com/womens-health/estrogen-metabolite-ratios/
How Platypus Sex Chromosomes and Bird Sex Chromosomes Linkage may have Same Origin
The determination of sex for several species has been genetic with females and males bearing different genes/alleles specifying their sexual morphology. Sex determination in animals in most cases goes hand in hand with differences in chromosomes through haplodiploidy or chromosomal combination of ZW, ZO, XY, and XO. This difference is often accelerated by a sex locus (main gene) accompanied by several other genes in a domino effect (Smith & Voss, 2007). There has been a generally accepted argument that the ZW and XY sex chromosomes underwent evolution in two separate branches at the same time (Namekawa & Lee, 2009).
However, there is substantial proof suggesting that there is the possibility of initial transition between the XY and ZW sex chromosomes like in the case of Xiphophorus maculatus bearing both XY and ZW systems within the same population despite the difference in location of genes between the ZW and XY sex chromosomes (Veyrunes et al, 2007). Due to the DMRT 1 gene found in the platypus X chromosomes that is usually possessed by birds, there is substantial reason to support the possibility of a common link between ZW and XY sex chromosomes (Smith & Voss, 2007) as cited in (Jennifer, 2006).
Smith and Voss argue that the proportion of chicken Z and human X orthologs noted in ALG2 is far way beyond what would be expected to be by chance, disputing the hypothesis currently in acceptance arguing that there are separate autosomal origins. Results obtained from research suggested that mammals and bird’s sex chromosomal regions originated from a common ancestral chromosome (Deakin, Hore, Koina, & Graves, 2008; Smith & Voss, 2007).The mammalian males have a combination of X and Ychromosomes to form the XY chromosomes while the females have two similar XX sex chromosomes. Comparing to birds, which have the ZZ-ZW sex determination system, their females are classified with heterogametic ZW sex chromosomes (Smith & Voss, 2007; Namekawa & Lee, 2009).
There is also notable similarity between the chicken W chromosomes and the mammalian Y chromosomes in their conspicuously smaller size as compared to their Z and X counterparts respectively, and also that they both contain fewer loci (Deakin et al., 2008; Smith & Voss, 2007). Deakin et al. (2008) further argues that as much as the mammalian X and Y chromosomes share homology between coding genes on the Y and X, and also within pseudoautosomal regions, the Y chromosomes are significantly variable and smaller in size as compared to the X. It is thus argued that this proves the theory that supports the evolution of heteromorphic sex chromosomes from a homologous autosome pair in a mammalian ancestor after the acquisition of a sex determinant locus by one member of the pair, which resulted in suppression, differentiation and recombination between members of the pair (Deakin et al., 2008).
The evolution of the Z and W bird chromosomes are also proposed to have evolved in a similar way from an ancient autosomal pair. This is supported by the high similarity between the ZW and XY chromosome properties. For instance, both the mammalian X chromosome and bird Z chromosome are highly conserved between species with the W chromosome being degraded in different groups of birds to varying extents (Deakin et al., 2008). Both the mammalian and bird X and Z chromosomes respectively are large in size, conserved between species, and contain many genes. They also appear to be sex-biased in their gene content (Deakin et al., 2008).
Veyrunes et al., (2008) test the hypothesis that argues the possibility of the bird ZW and mammalian XY system sharing homology with the platypus sex chromosomes. The research uncovers that homologous regions to the chicken Z chromosomes were evident, distributed sparsely throughout, principally on the X3 and X5 (Veyrunes et al., 2008).
The research conducted in this coursework was based on secondary sources of data that featured how platypus sex chromosomes and bird sex chromosomes linkage could have shared the same origin. The research uses three major sources to evaluate the possibility of the existing platypus and bird sex chromosomes sharing the same origin. These sources are selected on the basis of originality, extent of research conducted, methods of data analysis, methodology used in the research and authority of the authors, population size used in data analysis, and relevance to the study. This coursework reviews these sources, analyzing the arguments of the authors in relevance to the topic of discussion outlining their results and findings and providing a brief discussions to support the results.
Results and findings
Veyrunes et al. (2008) localizes and identifies BACs on the sex chromosomes on platypus. Male platypus mitotic metaphase chromosomes resulted from the hybridization of 32 BAC clones. Out of the 32, 18 mapped on a single X chromosome: two were mapped on X5p, two on X3q, five on X5q, and nine on X1q, while the remaining 14 had signals with both the Y and X chromosomes (Veyrunes et al., 2008). The extent of homology between human chromosome X and platypus chromosome 6 was confirmed by the results obtained by Veyrunes et al., previously established for seven XCR genes. Results obtained depicted the entire representation of the conserved region of the therian chromosome X, by platypus chromosome 6, which has been reorganized in line with chicken chromosome 4p, human X chromosomes, and opossum X (Veyrunes et al., 2008).
Results obtained from another study, which tested for the origin of mammal and bird sex chromosomes through mapping amniote sex chromosome loci locations in a salamander were as follows. Orthologs of 20 amniote sex chromosomes were meiotically mapped to ambystoma linkage groups. Most of the Z orthologs were found to map on a single ambystoma linkage group (ALG2). The results had a frequency of Gadj = 6.2, P = 0.013 which is far way beyond than would be expected by chance. Also, the XCR orthologs frequency on ALG2 was above what would be expected by coincidence, Gadj = 6.3, P = 0.009 (Smith & Voss, 2007). When ALG2 genes were searched against the full genome assemblies for chicken and human, they were found to be randomly distributed among chicken chromosomes with Gadj = 32.9, P = 9.7e-9 and human chromosomes with Gadj = 42.6, P = 6.9e-11, which hindered reciprocal amniote sex-chromosome loci (Smith & Voss, 2008).
Distribution of orthologies of sex chromosomes on ALG2 has been demonstrated to be beyond the likelihood of having occurred by chance through statistical analysis. The idea of the Z-W and X-Y chromosomal regions being linked to a prior ancestral chromosome of the amniote and amphibian lineages is inconsistence with the pattern of orthologies on ALG2 (Smith & Voss, 2008). Analysis done in the study showed that quite a good number of gene orders that were conserved between the autosomes and sex chromosomes of humans and chickens were conserved on the same chromosome of a salamander and interspersed. This implied that some of the ancestral chromosome gene content that gave rise to the Z and X sex chromosomes are still retained by the ALG2 (Smith & Voss, 2008).
Various reasons have been outlined in this review in support of the link between platypus and bird sex chromosomes arguing that there is a higher probability that they share the same origin. Among the reasons outlined include their similarities, which is beyond what would be expected to occur by chance. Taking for instance, there are significant similarities between the chicken W chromosomes and the mammalian Y chromosomes in their conspicuously smaller size as compared to their Z and X counterparts respectively, and both contain fewer loci.
The evolution of the Z and W bird chromosomes are also proposed to have evolved in a similar way from an ancient autosomal pair, which is supported by the high similarity between the ZW and XY chromosome properties. For instance, both the mammalian X chromosome and bird Z chromosome are highly conserved between species. In addition, both the mammalian and bird X and Z chromosomes respectively are large in size, conserved between species, and contain many genes. They also appear to be sex-biased in their gene content.
There was high similarity found between the variable dosage and partial relationship of the Z chromosome genes on chicken and that of multiple platypus X chromosomes. There was also shared similarity in dosage compensation features between the mammal X chromosomes and bird Z chromosomes with the platypus. Basing on the above provided evidence, one could possibly and confidently defend that there is substantial evidence to demonstrate that platypus sex chromosomes and bird sex chromosomes may have shared the same origin.
Deakin, J. E., Hore, T. A., Koina, E., & Graves, J. A. M. (2008). The status of dosage compensation in the multiple X chromosomes of the platypus. PLoS genetics, 4(7), e1000140.
Namekawa, S. H., & Lee, J. T. (2009). XY and ZW: is meiotic sex chromosome inactivation the rule in evolution? PLoS genetics, 5(5), e1000493.
Smith, J. J., & Voss, S. R. (2007). Bird and mammal sex-chromosome orthologs map to the same autosomal region in a salamander (Ambystoma).Genetics, 177(1), 607-613.
Veyrunes, F., Waters, P. D., Miethke, P., Rens, W., McMillan, D., Alsop, A. E., & Graves, J. A. M. (2008). Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes. Genome research, 18(6), 965-973.
Spectral characterisation of haemoglobin and its derivatives
One the functional proteins in vertebrates are the iron-containing haemoglobin which is one of the components of red blood cells (erythrocytes). Haemoglobin primarily carries oxygen to all body parts as its subunits have binding sites for oxygen molecules. While the globin groups provides binding sites for oxygen, the non-protein group known as the haem group which made up of porphyrin has not oxygen binding sites and has iron binding sites. After binding, haemoglobin becomes oxygenated and is known as oxyhaemoglobin (Costanzo, 2007). Deoxygenation occurs when the oxygen molecules are assimilated into the various organs and tissues including the alveoli leading to the formation of deoxyhaemoglobin. Other gases such as carbon dioxide, nitric oxide and carbon monoxide also have ligands which can bind to the haemoglobin ligands. When bound to these gases and iron, haemoglobin cannot transport oxygen due to the formation of methaemoglobin with iron, carbonmonoxyhaemoglobin with carbon monoxide and carbaminohemoglobin with carbon dioxide. These compounds must first be reduced by reductase enzymes to free up binding sites for oxygen but the process is difficult since such compounds are relatively stable. Failure can lead to diseases such as methaemoglobinemia (Jensen, 2009). Such diseases are manifested in the form of dizzy spells and general fatigue as the body oxygen required for energy production.
Deoxyhemoglobin and oxyhemoglobin absorb light of different wavelength and this is the basis of spectral characterization of haemoglobin and its derivatives. Generally, deoxyhaemoglobin absorb light of lower wavelength estimated to be 660 nm. On other, oxygenated blood tends to absorb light wavelength of 940 nm better.
The principal aim of this experiment is characterize and determine the absorption spectra of haemoglobin and its derivatives via spectroscopy by first isolating the blood.
Requirements and methodology
- To hypotonic shock, the cells contained in 5 ml of blood containing anticoagulant was lysed by mixing with 40ml distilled water, allowed to rest for 30 minutes followed by a 15 minute centrifugation at 1500g. After removing the supernatant, 9% w/v sodium chloride was added to make the solution isotonic.
- The resulting haemoglobin was divided into two portions and labeled A and B. An aliquot of A was diluted using isotonic saline to 0.8 units at 540 nm and using a spectrometer, its spectral characteristics were measured over 500 to 650 range. This was repeated when a few sodium dithionite were added to the cuvette containing the portion of sample A.
- To a portion of sample A, one drop of potassium ferricyanide was added to make methaemoglobin whose spectral characteristics were measured at 500 to 650 range.
- This procedure was repeated for aliquots of sample B and all the results recorded.
- To determine the content of the haemoglobin sample, 1 ml of pyridine and 1ml of 0.1M NaOH were added to the sample and thoroughly mixed in the fume cupboard
- Sodium dithionite crystals were added and absorption of the liquid formed measured at 557. Using an absorption coefficient of 34.4 mM-1 cm-1 was used to calculate haemoglobin concentration.
Results and discussions
The results were as follows:
Diagram 1: The spectral characteristics of haemoglobin sample B after adding sodium dithionite crystals
Diagram 2: The spectral characteristics of haemoglobin sample B without sodium dithionite crystals
Diagram 3: The spectral characteristics of haemoglobin sample B with potassium ferricyanide
Table 1: Showing the absorbance of Sample A under different wavelengths
Pigments including haemoglobins absorb light energy at various wavelengths. The spectrum of haemoglobin and other pigments is an expressional function measured using spectrometer. From the experiment, the change in the wavelength in the two samples was determined by oxygenation and deoxygenation and in the case of addition of potassium ferricyanide or sodium dithionite crystals as seen in the case of Sample B. These chemicals interfere with absorption capability of haemoglobin as they form fairly stable compounds when mixed with haemoblobin.
The measurement of the spectra of haemoglobin is important in diagnosis and treatment of blood poisoning especially when gases such as carbon monoxide and compounds such as iron and cyanide are involved (Jensen, 2009). Diseases such as methaemoglobinemia, carbon monoxide and cyanide can be treated can bet treated by giving the patients supplement oxygen (Salah, Samy & Fadel, 2009). When mixed with methylene blue, oxygen can accelerate the oxidation of these complex compounds that hinder the binding of oxygen to the haemoglobin ligands.
Haemoglobin is a vital protein in the body that ensures that energy required by all the body functions as it transports oxygen throughout the body. The differential spectral characteristics of oxygenated and deoxygenated blood are vital in treatment of diseases such as carbon monoxide poisoning. The presence of such compounds affects the spectral characteristics and this is the basis for diagnosing and treating these diseases.
Salah, M., Samy, N. & Fadel, M. (2009). “Methylene blue mediated photodynamic therapy for resistant plaque psoriasis”. J. Drugs Dermatol. 8(1): 42–9.
Jensen, F. B. (2009). “The dual roles of red blood cells in tissue oxygen delivery: oxygen carriers and regulators of local blood flow”. Journal of Experimental Biology (The Company of Biologists) 212 (Pt 21): 3387–3393.
Costanzo, L. S. (2007). Physiology. Hagerstwon, MD: Lippincott Williams & Wilkins.