Understand the Meaning of Heterozygous

Understand the Meaning of Heterozygous In diploid organisms, heterozygous refers to an individual having two different alleles for a specific trait. An allele is a version of a gene or specific DNA sequence on a chromosome. Alleles are inherited through sexual reproduction as the resulting offspring inherit half of their chromosomes from the mother and half from the father. The cells in diploid organisms contain sets of homologous chromosomes, which are paired chromosomes that have the same genes at the same positions along each chromosome pair. Although homologous chromosomes have the same genes, they may have different alleles for those genes. Alleles determine how particular traits are expressed or observed. Example: The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r). A heterozygous plant would contain the following alleles for seed shape: (Rr). Heterozygous Inheritance Complete Dominance: Diploid organisms have two alleles for each trait and those alleles are different in heterozygous individuals. Incomplete dominance inheritance, one allele is dominant and the other is recessive. The dominant trait is observed and the recessive trait is masked. Using the previous example, round seed shape (R) is dominant and wrinkled seed shape (r) is recessive. A plant with round seeds would have either of the following genotypes: (RR) or (Rr).  A plant with wrinkled seeds would have the following genotype: (rr). The heterozygous genotype (Rr) has the dominant round seed shape as its recessive allele (r) is masked in the phenotype.Incomplete dominance: One of the heterozygous alleles does not completely mask the other. Instead, a different phenotype is seen that is a combination of the phenotypes of the two alleles. An example of this is pink flower color in snapdragons. The allele that produces red flower color (R) is not completely expressed over the allele t hat produces white flower color (r). The result in the heterozygous genotype (Rr) is a phenotype that is a mixture of red and white, or pink. Codominance: Both of the heterozygous alleles are fully expressed in the phenotype. An example of codominance is AB blood type inheritance. The A and B alleles are expressed fully and equally in the phenotype and are said to be codominant. Heterozygous vs. Homozygous An individual that is homozygous for a trait has alleles that are similar. Unlike heterozygous individuals with different alleles, homozygotes only produce homozygous offspring. These offspring may be either homozygous dominant (RR) or homozygous recessive (rr) for a trait. They may not have both dominant and recessive alleles. In contrast, both heterozygous and homozygous offspring may be derived from a heterozygote (Rr). The heterozygous offspring have both dominant and recessive alleles that may express complete dominance, incomplete dominance, or codominance. Heterozygous Mutations Sometimes, mutations can occur on chromosomes that change the DNA sequence. These mutations are typically the result of either errors that happen during meiosis or by exposure to mutagens. In diploid organisms, a mutation that occurs on only one allele for a gene is called a heterozygous mutation. Identical mutations that occur on both alleles of the same gene are called homozygous mutations. Compound heterozygous mutations occur as a result of different mutations that happen on both alleles for the same gene.

Aqua Regia Definition in Chemistry

Aqua Regia Definition in Chemistry Aqua Regia Definition Aqua regia is a mixture of hydrochloric acid (HCl) and nitric acid (HNO3) at a ratio of either 3:1 or 4:1. It is a reddish-orange or yellowish-orange fuming liquid. The term is a Latin phrase, meaning kings water. The name reflects the ability of aqua regia to dissolve the noble metals gold, platinum, and palladium. Note aqua regia will not dissolve all noble metals. For example, iridium and tantalum are not dissolved.Also Known As: Aqua regia is also known as  royal water, or nitro-muriatic acid (1789 name by Antoine Lavoisier) Aqua Regia History Some records indicate a Muslim alchemist  discovered aqua regia around 800 AD by mixing a salt with vitriol (sulfuric acid). Alchemists in the Middle Ages tried to use aqua regia to find the philosphers stone. The process to make the acid was not described in chemistry literature until 1890. The most interesting story about aqua regia is about an event that occurred during World War II. When Germany invaded Denmark, the chemist George de Hevesy dissolved the Nobel Prize medals belonging to Max von Laue and James Franck into aqua regia. He did this to prevent the Nazis from taking the medals, which were made of gold. He put the solution of aqua regia and gold on the shelf in his lab at the Niels Bohr Institute, where it looked like just another jar of chemicals. de Hevesy returned to his laboratory when the war was over and reclaimed the jar. The recovered the gold and gave it to the Royal Swedish Academy of Sciences so the Nobel Foundation to re-make the Nobel prize medals to give to Laue and Franck. Aqua Regia Uses Aqua regia is useful to dissolve gold  and platinum and finds application in the extraction and purification of these metals. Chloroauric acid may be made by using aqua regia to produce electrolytes for the Wohlwill process. This process refines gold to extremely high purity (99.999%). A similar process is used to produce high-purity platinum. Aqua regia is used to etch metals and for analytic chemical analysis. The acid is used to clean metals and organics from machines and laboratory glassware. In particular, its preferable to use aqua regia rather than chromic acid to clean NMR tubes because chromic acid is toxic and because it deposits traces of chromium, which ruin NMR spectra. Aqua Regia Hazards Aqua regia should be prepared immediately before use. Once the acids are mixed, they continue to react. Although the solution remains a strong acid following decomposition, it loses effectiveness. Aqua regia is extremely corrosive and reactive. Lab accidents have occurred when the acid exploded. Disposal Depending on local regulations and the specific use of aqua regia, the acid may be neutralized using a base and poured down the drain or the solution should be stored for disposal. Generally, aqua regia shouldnt be poured down the drain when the solution contains potentially toxic dissolved metals.