Answer:
<em>Chargaff: </em>The work of Erwin Chargaff has major contributions towards understanding of DNA structure as a double helix. Although, he didn't propose the DNA as a double helix, but he was the first scientist two establish two rules that lead to the discovery of DNA as a double helix. Briefly, he proposed that (1) in any DNA, the amount of Guanine are always equal to the amount of Cytosine and likewise, the amount of Adenine are always equal to the amount of Thymine; and (2) the amount of guanine, cytosine, adenine and thymine bases are different in each species. This observation supported the idea later that DNA is the heriditary material rather than proteins.
<em>Franklin</em><em>:</em> Rosalind E. Franklin is known for her work on understanding the molecular structure of DNA via X-Ray diffraction. For that, she exposed crystallized DNA moleculeto X-rays and some of the rays were deflected back thus forming a diffraction pattern. She was the first scientist that produces real images of DNA explaining its molecular structure. As an example, I have attached the Photo 51 she took while working at King's College London. Her work led to the actual discovery of DNA as a double helix (Watson and Crick Model) which we know today.
<em>Watson and Crick</em>: James Watson and Francis Crick proposed the 3D structure and model of the DNA helix which we know as of today. Precisely, their work explained that DNA is a double-stranded, antiparallel, right-handed helix. Further, the nitrogenous basis proposed earlier (A, T, G, C) are attached to sugar-phosphate backbone via hydrogen bonds. It is one of the major discoveries in molecular biology.
Answer:
Explanation:
C is a volcano.
A volcano is as a result of igneous activities.
Volcanoes are landforms formed by the extrusion of magma on the earth crust.
Magma that reached the crust is called a lava and it is made up of molten rock minerals.
When the lava cools, it forms the rocks we see on the crust.
The mechanism by which minerals forms in a melt is known as differentiation. Differentiation is the process by which minerals separates from an originally uniform mixture. As temperature varies within the earth, new minerals forms by combining elements and others are broken down.
In a Volcano, the melt is the mineral soup. The melt is at a very high temperature. As it rises through the vent to the surface, temperature decreases very rapidly. When temperature reduces rapidly, it is difficult for large minerals to form. Minerals crystallise out of the melt according to the Bowen's reaction series and the composition of the melt.
We must note that, as the melt rises through the crust, it assimilates some crustal materials. Some of these materials can change the original composition of the melt as it rises. If such a melt orginates from the mantle, it mixes with crustal rocks and forms a rock bearing some mafic and felsic minerals.
It is typical to find fine grained rocks that lacks crystals in such a place. This is because the cooling of the melt was rapid and crystals could not form properly.
Answer:
This can be caused by mating differences, sterility or environmental barriers that eventually lead to the adaptive splitting into two species. ... However, reproductive isolation is not sufficient but internal barriers to gene flow are required for speciation to evolve.
Explanation:
I hope this helps I'm not so good at explaining.
Lung diseases........................
Answer: 2 alleles
The number of the allele that a gene contains could be various. The allele will determine the phenotype of the organism, so more allele means more possible combination. There is only 1 gene that control the corn height and that gene only has two alleles. So, the total allele that controls the corn height should be: 1 gene * 2 alleles/gene= 2 alleles
