Mad Cow Disease

Mad cow disease is a neurodegenerative disease of cattle. it is caused by prions. priors are the misfolded proteins . their normal form is present in the cells. abnormal misfolded form becomes infectious and is called prion. a prion converts same kind of normal protein into abnormally folded protein.these abnormally folded proteins aggregate to form plaques which are toxic to nerve cells and cause death of nerve cells.
the cases of this disease  were reported in UK and Canada in 1990s.at present this disease is near eradication .
cause of spread of this disease was feeding the cattle on meat and bone meal. if this meat and bone bone has come from infected cattle it can cause mad cow disease in the fed cattle.the chances are high if the cattle feeds on brain or spinal cord of infected cattle   .
the appearance of symptoms may take several months or some years.the symptoms include abnormal walking of cattle due to less of muscle control.abnormal behavior of cattle, cattle goes into coma and ultimately dies. this disease is also called bovine spongiform encephalopathy.
man can also get infected by eating meat of infected cattle. man gets variant Creutzfeldt Jakob Disease by the prions that cause mad cow disease in  cows. mad cow disease does not spread by consuming milk of infected cows.

By:Ashwani,bio-teacher ,Phagwara.

Epigenetics

Epigenetics simply means something above or on top of the genetics. it involves the study of all the mechanisms that  changes the expression of genes by turning them switch on or switch off. the structure of gene is not altered but just turning the genes switch on or off changes the expression of genes.one such mechanism is methylation of DNA bases which prevents the expression of that DNA. the modification in his histone proteins of chromosome that tightly squeeze DNA in chromosome will prevent the expression of that DNA.the modifications in histones that relax the DNAwill allow the expression of DNA.it is due to epigenetics that skin cells are different from brain cells and liver cells. all of these cells have same kind of genes but in different types of cells different genes are switched on and switched off which makes these cells unique and different from others. our environmental also effects the turning on and off of genes for example when we spend more time in sunlight the amount of melanin increase in skin. what we eat also affects the turning on and off of genes. for example eating sugar rich diet cause more formation of  insulin.our mental stage also effects the turning on and off of genes .stress causes formation of cortisone hormone..for formation of cortisone specific genes are switched on. switch on and switch off of genes is a normal thing in body of all living organisms,but when this mechanism occur abnormally it results in diseases like cancer and Alzheimer.

By: Ashwani, bio-teacher ,Phagwara.

Prions

prions cause several neurodegenerative diseases in humans and other mammals.prions are proteinaceous infectious agents.they don't have any nucleic acid.this is a unique thing about prions. all the known pathogens like bacteria,viruses and others all have nucleic acid.prions retain their ability to infect even after treatment with ultraviolet radiations or other treatments that destroy nucleic acid.scientists have discovered that prions are the misfolded proteins with abnormal structure .when this abnormal protein binds to same type of normal protein it induce the latter to change its conformation . the newly distorted protein then induces the misfolding in other similar proteins. in this way it become a chain reaction. prions cause mad cow disease also known as bovine spongiform encephalopathy. scientists believe that infected cows may transmit infection to humans .it humans this infection causes CJD that is Creutzfeldt-Jakob disease.the process by which change in structure of protein occur is not clear and research is going on to understand the mechanism .in CJD disease scientists have discovered spongy structure of Brain in dead victims.this sponginess is caused due to holes in brain due to cell death . scientists believe that abnormal shaped protein becomes toxic to cell and causes cell death.prions can be transmitted by eating infected part of victim,by inoculation into brain or skin.some prion cases of CJD and GSS have shown inheritance pattern perhaps this is due to mutation in gene which changes amino acid pattern in a protein and  convert it into a prion.

By:Ashwani, bio- teacher, Phagwara.

Parathyroid

Thyroid

How do mosquitoes locate their victims?

1.Eyes:Mosquitoes use their eyes to locate their victims. research has shown that people wearing dark colour clothes like red, black, navy black etc are more likely to be easily located by the mosquitoes .
2. Blood type : people with blood group O  are to twice attractive to mosquitoes than those with Type A. most of people produce blood group specific secretions mosquito can detetect.
3. carbon dioxide : carbon dioxide is attractive to mosquitoes .they can sense carbon dioxide from a distance over 150 feet away.so more carbon dioxide one exhales,more attractive he/she is  to the mosquitoes .as we exhale carbon dioxide through nose therefore while sleeping or resting  there is more carbon dioxide around our head region.no surprise often  we hear  buzzing sound mosquito offer in our ears.
4. Body heat and sweat: Mosquitoes  can  also  detect  heat  of our body  and  sweat  also.  our sweat  contains  lactic acid, uric acid, ammonia  and some other compounds. the mosquitoes can sniff these compounds . So  sweaty peoples  are likely    to be more attractive  for the mosquito.  after strenous exercise  we  sweat more,  our body  emits more  heat . in such  state  we are more likely  to be attacked  by the mosquito.
5.Type of bacteria on skin .In one study,  humans were divided into those two groups. One group  that was  highly attractive to mosquitoes and other one with  those who were not.The attractive ones had more of certain microbes on their skin than the unattractive ones.
6.pregnancy:One study revealed that pregnant women are twice as attractive to Anopheles mosquitoes  as non-pregnant women.perhaps it was because women in late pregnancy exhaled 21 percent more volume of breath,hence more carbon dioxide  than non-pregnant women. Moreover, abdomens of pregnant women are about 1.25 fahrenheit  warmer than non pregnent women.
 7.beer.researchers found that significantly more mosquitoes come close to our body after drinking a 12-ounce beer.it was due to increased ethanol content in sweat and skin temperature after drinking beer)

Arthropoda

Arthropods are  cosmopolitan .They are found almost in every habitat. They are found in desert ,inside soil, in freshwater, in marine water, in snowy areas and also as parasites. Most of these are solitary or gregarious. some form colonies with social organisation.Body is divided into 3 regions head ,thorax and abdomen. In some species head is fused with thorax  to form cephalothorax .Segmentation is external. lnternal septa are absent. Symmetry is bilateral. Coelenterates are triploblastic animals with organ level of body organisation . Spaces in between organs merge and form blood filled cavity called haemocoel.Head is formed by fusion of 6 segments .it has various types of mouth parts. Eyes are compound . Exoskeleton is mostly made up of chitin. it undergoes moulting or ecdysis at intervals . Insects have wings made up of chitin. they have jointed legs and other appendages. Digestive canal is complete . Blood circulatory system is open type. Blood vessels cannot be differentiated into arteries and veins. Blood is colourless and is called hemolymph . Excretory system consists of green glands, malpighian tubules. gills, tracheae,book gills, book lungs, respiratory siphon are respiratory organs found in various arthropods. Nervous system consists of various  ganglia ,nerves and nerve plexus. Most arthropods are unisexual, few are hermaphrodites. fertilization can be external or internal. Parthenogenetic development of eggs into young ones is found in many arthropods like Honey Bee cockroach grasshopper etc. Asexual reproduction is absent. Development may be direct or indirect involving one or more larval stages. series of changes that convert larvae into adults are together called as metamorphosis.