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What Are Polar Bears Made Of? by Lauren Filius

Genetic aspects- There is lots known about other things related to polar bears, but little is known about their genetics. This is because of technical difficulty and high expenses. But now scientists are able to perform genetic analyses on any organism. This genetic information will help to understand the behavior, ecology, life history and evolution of the polar bear population.--------------------------------------------------------There are 8 main groups of bears including polar bears and all of them have in common a nearly identical karyotype and 74 chromosomes. This mitochondrial DNA is passed from mother to baby much like any other organism. Polar bear lineage has revealed that they might be linked to a large group of brown bear lineage. But further research proved that 3 polar bear lineages grouped with the brown bears and 1 polar bear lineage grouped with the spectacled bear.It is a known fact that polar bears and brown bears have produced fertile hybrids. So the question still remains that if polar bears have evolved from brown bears or if a female produced a hybrid, and increased the polar bears population by inbreeding.--------------------------------------------------------Scientists use different sources on a polar bear for genetic research. For example, hair, both nDNA and mtDNA can be extracted, and then are shipped to be analyzed. DNA can also be extracted using QIA columns from the skin tissue in the ear. Then you can use a process called polymerase chain reaction to copy the DNA. This DNA can also be studied from cell nuclei, and if it matches the mitochondrial DNA. Then a bears lineage can be determined.--------------------------------------------------------You can determine the age of polar bears from the cementum growth layers in a premolar tooth, Diet can be determined from this also. Polar bears have an incredibly large diet because in the months of May through june, they hibernate. Polar bears will use their internal metabolism during these months, they will not eat or drink anything. But they will absorb urea (a waste product found in the bladder)as a building block for amino acids.This nitrogen reprocessing allows the bear to be a self contained metabolic factory,which is particularly important for the denning female bear,as she will generate enough protein to even make a new cub. The cycle of urea plus glycerol to make amino acids is also performed by the male bear, and in fact the male makes enough protein in the form of blood proteins, such as albumin, to store just as much energy as the female.The blood protein Albumin carries fatty acids around the body for metabolism. Fat will go down by 40%,while skeletal muscle and other proteins will remain the same.There are two genes that are thought to trigger hibernation and allow enzymes to burn fat.One of these is pyruvate dehydrogenase kinase (PDK). This enzyme has a major effect on pyruvate metabolism and allows a modification of the fatty acid production through acetyl co-A, and the tricarboxylic acid cycle to be changed.-------------------------------------------------------Polar bears are also subject to PCBs because of their position on the food chain, and their diet. PCBs are pollution from the environment and it effects polar bear's cell production and ability to produce offspring. It will cause cellular dysfunction in the white blood cells that will decrease resistance to diseases. PCBs diminish body weight because they don't allow muscle cells to duplicate. If PCBs become more present in the environment, then polar bears might become an endangered species.-------------------------------------------------------- There are differences between male and female polar bears, for exampl;Weight will vary, but there is considerable difference between males and females. Males weigh anywhere from 800 to 1,500 pounds while females average 300 to 550 pounds. A female is usually 5-8 ft, while males are 6-8 ft long. Males reach sexual maturity when they are 3-5 years old. And females when they are 4-5 years old. Newborn cubs, if they are male will be 12 inches long, female cubs will be 11 in. You can tell a females' tracks from a males because her's will be much smaller. female polar bears will not hunt as often as males, they will scavenge off they males' remains, and only hunt if food is scarce. Males will make more risky attacks, while females will look for easier prey.--------------------------------------------------------A common misconception of polar bears is that some people believe that polar bears' fur is white because of recessive genes. But polar bears are not white because they are albinos. Since polar bears are mostly dominant, their fur color being white, is a dominant trait. So polar bears are not white because they are albinos. And also because they have black skin which contains a high amount of melanin, so that light can be absorbed. Variations have occured in polar bears over generations due to global warming. These polar bears have grown increasingly thinner because their hibernation period is shortened. So this will cause future generation to become thinner and maybe even endangered.-------------------------------------------------------Variations have also occured in a polar bear's genotype due to variations over time. Such as being left-handed, for catching seals easier. These mutations are a result of neutral mutations, which are changes in the genotype that are not harmful to the organism's health. Thats why harmful mutations don't stay in the phenotype because the carrier has decreased fitness therefore having less descendants. it all goes back to Darwin's theory of survival of the fittest. Mutations have helped polar bears adapt to their harsh environment. In Norway scientists have had many encounters with transgender female polar bears. This trend is continuing to spread throughout the arctic. These masculinized females have their internal organs, while having the outside genitalia of a male. About 10-20 percent of bears in some populations show this absurdity. But it is not deadly, seeing as females succesfully give birth and raise cubs. This mutation is thought to come from the deadly pollution called PCBs. Polar bears are continually threatened by diseases, like the parasite worm Trichinella, that they contract by eating infected seals. And PCBs are also dangerous to polar bears and cause the immune system to break down. Bears can also catch distemper from infected meat. But no hereditary diseases threaten polar bears.-------------------------------------------------------Scientists are constantly trying to prevent inbreeding of polar bears by moving them to different locations in the circumpolar north. They're trying to keep the males at a 2:1 ratio. But polar bear mothers will tend to adopt cubs from other litters.Polar bears haven't been experimented with in th genre of selective breeding, because of their size, possible rareity, and because people are scared of them.I think thats the way it should stay, polar bears are to beautiful to be messed around with.

Refrences

Links

Genetic structure of the worlds polar bear population
Do all polar bears have recessive genes or is white their dominant color?
Genetics of the bears of the world
Keeping polar bears alive

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