Mutagens can be classified into two broad categories :

Physical Mutagens : Radiations are the most important physical mutagens. These are of two types.

• Ionizing Radiations :  These include X-rays, gamma-rays, alpha-rays and beta-rays. These cause breaks in chromosomes and cells show abnormal cell division.
• Non-Ionizing Radiations : These include UV rays. They have longer wavelengths but lower energy, and thus are insufficient to induce ionization. Thymine dimer formation is the major effect.

Chemical Mutagens : Large numbers of chemical mutagens exists. These are more harmful. Usually divided into two groups

• Mutagenic to both replicating and non replicating DNA - Nitrous Acid
• Mutagenic to Replicating DNA - Acridine Dyes, Base Analogues

Hello Antara,

Break down of excess of amino acids i.e protein into urea is done by the liver.  So the maximum amount of urea will be found in the vein leaving the liver. Hepatic Vein leaves the liver carrying the largest amount of urea. The hepatic vein carries blood away from the liver to the vena cava which transports it back to the heart

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Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.

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Meiosis II reduces the amount from 2C to C in gametes and when these gametes get fused the amount of DNA become again 2C. Thus meiosis II helps keep DNA amount fix generation to generation.

Meiosis is the production of four genetically diverse haploid daughter cells from one diploid parent cell. ... Homologous pairs of cells are present in meiosis I and separate into chromosomes before meiosis II . In meiosis II , these chromosomes are further separated into sister chromatids

Hi Nasem,

Vasa recta is a capillary network which supply blood to the medula. it is highly reduced in Cortical nephrons.

In cortical nephrons it is reduced because,it is concerned with the concentration of the urine.

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Collagen is the most abundant protein in the animal world which accounts for 30% of total protein content in the human body. Collagen is a key constituent of all the connective tissues. It is found in joints, bones, skin, hair, etc. This protein helps the skin to move, stretch and rebound into shape. It is present throughout the body and keeps the cells together. Without collagen the body would fall apart into pieces.

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RuBisCO is very important in biology and ecology because it catalyzes the primary chemical reaction by which inorganic carbon permanently enters the biosphere. RuBisCO is also the most abundant protein in leaves and the most abundant protein on Earth.