To begin with, dominant is an allele that is usually expressed in an individual who is heterogeneous. Recessive allele on the other hand is that trait that is only expressed in a homozygous situation. In Dominant allele, single copy of a gene is sufficient to express its character, and it is usually denoted by the capital letter. With recessive allele, it requires two copies of the gene to express its character, and it is usually denoted by small letters. If a mom for instance is Aa, and a dad is aa, we see that here the A is dominant. What this portends for their offspring is that it will have 50 percent chances of taking up all the characteristics of A. In the case of a dominant allele, what is needed for that characteristic to manifest is one allele, however, for the recessive, both parents have to contribute the recessive allele for the trait to be manifested in the offspring (Clark, et al., 2003).
An autosomal trait is that trait that is passed on to an offspring via genes, it, however, does not determine the sex of that individual. The opposite of that would be sex-lined traits which are likewise inherited through genes though these ones do determine the sex of an individual. Some examples of autosomal traits are inability or ability to roll the tongue, widow’s peak or continuous hairlines among other. Autosome dominant traits occur due to a dominant allele that is present in one of the autosomes. For this allele to be manifested in the phenotype, it has to be inherited from either of the parents. Because of this therefore, any child stands a 50 percent chance of inheriting the allele and showing the trait that is inherent in one of the parents (Clark, et al., 2003). Example of sex-linked trait is color blindness. Males have Xy chromosomes and females XX chromosomes. In that regard, therefore, in order for a female to be colorblind, then both X chromosomes need to be recessive for this allele. If any of the other allele does not have this recessive trait, then there would be no colorblindness. On the other hand a male who is recessive for this trait on his X chromosomes would contract colorblindness.
DNA was discovered in 1869 but became a recognized genetic material a century later. Swiss medic student called Johann Friedrich Miescher found it by coincidence when he was working on some white blood cells that he had taken from the pus out of a drained surgical wound. He realized that the nuclear had an abundance of phosphorous and was equally acidic. He thus named it nucleic acid, a name it has retained to dat. It was not until the early 1950s that scientists recognized it as a genetic material. Fredric Griffith had in 1920 discovered that bacteria had the capacity to acquire something with each other that would see harmless bacteria turned into deadly bacteria. This was further pursued by a group of scientists led by Oswald Avery who was convinced that it was DNA that caused that change. In 1953, Alfred Hershey and Martha Chase found out that the virus that they had been working on injected only the DNA into a bacteria cell so as to infect it. Further discovery of the DNS structure was kicked off by Erwin Chargaff who found out if the DNA was broken down into numerous components, then the amount of guanine that was fluctuated from one of the organisms to the other was always equal to the cytosine that was present (Dahm, 2005). Further, the amount of adenine was the same amount of thymine. Scientist James Watson, Francis Crick and Rosalind Franklin would then realize why ratio was crucial to the structure of DNA. Watson and Crick used Franklin data on the shape of the DNA molecule which showed the DNA as taking the structure of a double helix. This inspired them to synchronize Franklin’s data with Chargaff’s rules enabling them to finally crack the code on the structure of DNA.
Formation of proteins or protein synthesis takes place in two processes which are transcription and translation. These are the two main processes that link a gene to protein. That said, the bridge between DNA and protein synthesis is the RNA. DNA and RNA are chemically similar. The only difference is that RNA contains ribose as its sugar, and secondly, it substitutes the nitrogenous base uracil for thymine. At the transcription stage a DNA strand gives a template for synthesis of a contemporary strain of RNA. It is at this process that any type of RNA is synthesized from a DNA template. Gene transcription produces a messenger RNA molecule usually written as mRNA. During translation process, the information that is contained in the form of nucleotides in the mRNA and is the one that determines the amino acid sequence of a polypeptide. The process of translation occurs at ribosomes (Troopp, 2008).
DNA -> RNA -> protein
Clark, D. P. et al., (2003) Molecular Biology London: Elsevier
Troopp, B. E. (2008) Molecular Biology: Genes to Protein New York, NY: Jones & Bartlett Learning
Dahm, R (2005) Fredrick Miescher and the Discovery of DNA Marx Plank Institute of developmental Biology. 278(2): 275-288