DIGESTIVE SYSTEM OF MAN

The organisation of the is the digestive system is the same as in rabbits; it consists of the alimentory canal and the associated  digestive glands ,the PANCREAS and LIVER .However , in  contrast with the rabbit ,the  digestive system of the man shows  the following pecu larities ; 1 The mouth has three pairs of salivary glands ,i.e., a pair of parotid ,apair of sub-maxillary and apair of sub lingual glands  .                            2 . The mouth cavity has 32 teeth on both the jaw aand the dental formula of the man isI2/2,C1/1 ,PM2/2 ,P3/3 and the dental formula of the child is I2/2 ,C1/1 ,PM2/2, M0/0 witha total of 20 milk teeth .However ,molars erupt only in the adult . 3 The oesophagus is 20-30 cm long  but  the small intestine  is about 7.5 m length  and about 2.5cm on width . 4 The colon measures from 1.2 -1.5 m in length and  and about 8cm in width .However the rectum is only 15cm long .5 . The liver ,divided into large right an small left lobes , weighs about 1.5kg .6 .The pancreas is whitish racemose gland.                                                                                                                                                                                         FOOD                                                                                  Any matter ,other than oxygen, that an animal takes into its body to make its part is called FOOD.It is  important to animal and plant  in the following  respects ;                                                                         1; It is used as fuel to release energy during the respiration .The energy is required for various life activities . 2;It is used as building material  to make new tissues  and thus cause growth .                                      3; It is used  as repair material for broken tissues and cells .4; It provides material  to form certain essential substance and  close [e.g . hormones ,enzymes ,etc ] in the body .                                                                                                   FOOD COMPONENT                                                                                                                The food that animal eats consists of organic and inorganic substances .These substances are called food components or food constituents or food stuffs. These include carbohydrates, lipids,proteins,vitamins ,mineral salt and water .The former four are organic constituents  and the latter two are inorganic constituents .Let us learn about these .                                                                                                      1.Carbohydrates .These  are compound of carbon , hydrogen and oxygen .The ratio  of hydrogen and oxygen in them is as in water , that is 2:1 . These compound usually make the bulk of the food and are chif sources of energy  in the body , one gram of a carbohydrate  yields 4.1 calories .The carbohydrates  include sugars ,starch , glycogen and cellulose .                                                                                                                2.These include fats and oils .Like carbohydrates ,these are also made of carbon , hydrogen  and oxygen  but the ratio of hydrogen to oxygen in them is not as in water ; in fact , the oxygen is much lesser in them  as compared to carbohydrates .Like  carbohydrates , these are also used  for producing energy  in the body and these produce more energy  than carbohydrates.                                                                                    3.Proteins ;These are large molecules  of carbon, hydrogen and oxygen  and nitrogen .The last one is essential  constituent of the proteins hence  the proteins are called nitrogenous compound .Some proteins also contain either sulphur or phos phorous or iron . Each proteins is made of smaller  simple units  called  amino acids .The haemoglobin is a large ptotein molecule .Albumin , globulin ,fibrinogen etc., are other example of protein                                                     

RABBIT;DIGESTIVE SYTEM

The digestive system of rabbit roughly correspond in their parts to those frog but each region is more developed and the division of labour reaches  a higher development of rabbit .The digestive system is concerned which is a complex process consisting of all changes which occur in food  with the alimentary canal from the time it is taken into the mouth until it has been  built up into actual body substance or used to supply body energy .These changes may be arranged  in order under four heads ;[1] digestion [2] absorption [3] distribution [4]assimilation .                     The digestive system of the rabbit consists of alimentary canal and associated glands such as liver and pancreas  that are situated outside the alimentary canal  but pour their secretion  into it .                                                    ALIMENTARY CANAL     ; Since the rabbit is hervivorous ,its alimentary canal is  very long coiled tube , begining at mouth and end at anus .Starting  from the mouth end , it consists buccal cavity , pharynx,oesophagus ,stomach ,small intestine and large intestine .                                                                                      BUCCAL CAVITY                                                             The mouth of rabbit is terminal and relative small .It is bounded by the lips which are movable .The upper lips is divided in middle to expose the incisor teeth ,a condition which is the advantage in gnawing .The buccal cavity is seperated from the respiratory channel  by the palate  which form s somewhat arched roof of the mouth cavity has the skeletol  foundation of the horizontal processes of the premaxillae ,maxillae  and palatine bones .It is  known as the hard palate ; its hinder part , which is purely  formed  by connective tissue and muscles , is called the soft palate , the free border of which  projects into the pharyngeal  cavity .The surface of the entire palate  particularly that of the soft palate is provided with numerous palatine glands whose secrrtion of mucus helps to keep the mouth  cavity moist The hard palate is also provided with palatine ridges or rugae [most well -developed in  carnivores ] which give a washboard -like  character to the palate  thus help in securing a surer grip  of the food .In the anterior part of the mouth cavity  there are two very smalll naso -palatine openings  which join the buccal cavity  with the nasal cavity .The posterior  internal nares  lie at the posterior end of the  soft palate  and open into the hinder part of the nasal chamber .The glottis is situated under the floor  of the pharynx and leads  into the trachea .Its opening is guarded by a bilobed  cartilaginous  flap the epi glottis, which prevent food from entering the  wind pipe or trachea .The eustachian  tubes open into the posterior nasal chamber .                                                                                                                                      The muscular and slightly protrusible  tongue lies along the floor of the mouth cavity  and is attached just in front of the hyoid  and is directed forward .The  tongue is subdivided into  the hard posterior part and the  soft anterior portion. The side of the posterior part bears the foliate papillie.On the  upper surface of the hard region  are teo circumvallate papillae, each with the ring like depression round it .On both of these papillae  and also on the tip and sides of  the soft anterior portion taste buds are collected .Since the tongue is capable of great variety  of movements ,it serves  many useful proposes .It is auniversal- tooth brush .In furred  animals ,it also act as a curry  comb .The mucous membrane  coverig the tongue has numerous minute  finger shaped papaillae  which contains nerve cells and hence do the work of organs of  taste .                                                                                      

MENDAL'S EXPERIMENT

Mendel's conclusion about inheritence of characters were based on his hybridization  experiments  in which  he considered  either one pair of contrasting  characters  involving  cross between plants with these characters .The  cross involving only one pair of  contrasting  characters is called monohybridization  and the related experiment is callen monohybrid experiment  or monohybrid cross .Likewise ,the cross involving two pairs of contrasting characters  is called dihybridization  and the related experiment is refered to as dihybrid experiment or cross .          Mendel's series of experiment  involved  seven pairs of contrasting characters  of the edible garden pea , pisum sativum namely ,smooth and wrinkled seed ,yellow and green peas , tall and short stems,axial or terminal flowers ,white or grey seed-coats ,yellow or green cotyledons ,etc peas are normally self -pollinating but mendel tried the experiment of transferring the pollen of one variety of pea to the stigma  of the other .        MONO HYBRID EXPERIMENT ;Mendel first cross pea-plants differing  in a single pair  of contrasting characters ,such as tallnesss or shortness of plants .Thereafter ,the seeds obtain from these plants i.e., the parental plants [p] were sown to obtain plants from the fist felial  generation ,indicated by f1 in abbreviated form .The flower of the f1 generation were allowed to second generation ,indicated by f1 in abbreviated  form. The flowers of the f1generation were allowed to self pollinate.All  the resultant seeds were collected  and sown to give the second filial or f2 generation .In this ,mendal found tall plants  and short plants in the proportional  of 3 tall to 1 short -finally all the plants of the f2 generation  and from the resultant weeds an f3 generation was obtained .Seed from the short plants of the f2 generation gave rise to nothing but  short plants  in the f2 generation .But the tall of f2 didnot all behave in the same  way .One third  of them gave rise  to nothing  but talls in thef3 , but  the other two thirds  segre gated like the plants of the f1 generation, giving rise to the short and tall plants  in the proportion of 3to 1 .                                                                                                 As a result of his experiments  mendal was able to state certain principles or laws  which now form the basis for all studies  of heredity or genetics [1] Law of Paired Units ; There are unit carriers  of heredity which occurs in pairs .One of each  pair come from the mother while  the other came from the father  . The unit carriers were caslled by mendel determiners  or factors but now they are known as genes . [2] Law Of Dominance ; when two hereditary units of pair are unlike ,the one which functions and produces  its character or effect is called dominant while the others whch remains undeveloped or unexpressed is called recessive .If a plant has one dominant and one recessive  gene , it exhibits the dominant  trait .[3] Law Of Segregation ; That is , the unit character or the gene  keep thier identity and in each generation they are free to seperate from each other and to be redistributed in the offspring .                                                                                     In the above  experiment  when two  of the tall plants obtain from cross of  a tall  and short peas were crossed , some  of the resulting pea plants [f2]  were tall and other short . This  led mendal to the concept of segregation .Thus the tall plants of f1 generation  have genes or factors for  both tallness or shortness .When these f1 plants  plants are crossed some of the offspring  recieve a gene for tallness  from each parent ,others recieve one gene for tallness  and other for shortness ,while  athird group of plants  get two genes for shortness                               

WATSON AND CRICK'S MODEL OF DNA

In 1953  ,James Watson and FrancisCrick proposed that the DNA molecule consists two poly nucleotide strands , each coiled  in a righthanded helix .The two strands of the double helix  are held together  by hydrogewn bonding between the nitrogenous bases  of adjacent nucleotides.For each complete twist of the double helix  there are 10 pairs of nucleotides , each twist measures 3.4 nm.      

The two polynucleotide  strands of a DNA molecule are not identical .They are complementary . Where adenine strands , thymine  is found in other .Where cytosine occurs in one strands , the guanine is present in the complementary strand .Altogether  there can be several thosands of nucleotides in aDNA molecule .The exact number depends upon the  origin of the DNA .The sequence in which the pairs of bases occurs  also differs in DNA from different species .In theory  the numbers of permutation s of the bases  is indefinite .    REPLICATION OF DNA ; The DNA produces its exact copy .The formation of its replica by DNA  molecule is called replication .They include despersive conservative and  semi conservative methods .Synthesis of DNA  requires  an enzyme  called  DNA  ligase. In despersive method , the old DNA mlecule should desintegrate and two new DNA  molecules  would be synthe sized again from the despersed constituents .Inconservative  method  of replication , out of two DNA  molecules formed ,one molecule would retain or conseve two old strands  and other will carry two newly synthesized  strands ,in this , no part  of the parent molecule would present  be half conseved  in each DNA molecule .Ther is sufficient  evidence  to prove  that the  replication  of the DNA takes  place by the semi conservative methd .The semi  conservative replication  takes place as follows; The hydrogen bonds between the base  pairs break at one end .Consequently,two strands unwind .Each strands  act as mould or template on which a new polynucleotide  strand is made.This gives a rise to two molecules of DNA ,identical to each other and which are replica of the original molecule ,carrying an old an new strand , Experimental evidence that DNA replication is semi conservative was  obtain by messelon and stahl [1957]  in escherichia coli . DNA as the herediatory  substance  Chromosomes the carriers of herediatory  characters , are mainly composed with nuclearproteins along with some other chemicals .The nucleoproteins  have two components,the nucleic acids and prteins and therefore .one of those should constitute  or act as herediatary  genetic material .Findings of certain experment  have  established  that the nucliec acid ,.not the proteins contains genetic information .                                       Transformation experiment ,first conducted by griffith and then repeated by others , have proved that the DNA is a genetic material. Griffith [1928] noted two distinct strains of bacterium pnemococcus , the s-strain and r-strain . The s-strain bacterium is enclosed in a capsule  ,and when when inoculate on to an agar-based  medium ,it  grows into a smooth shining colony .The r -strain bactrium lacks capsule  and its colony is rough and dull in  appearence . The s-strain bacterium is virulent ,whereas  the bacterium of r-strain is non virulent                       
 

NUCLEIC ACIDS AND PROTEIN SYNTHESIS

Chromosomes, the vehicles of heriditary characters ,are composed  of chromatin  which mainly consists of nucleoproteins  though other substances are known to be present in it .The  nucleoprotein as the name suggests , is a complex of nucleic acid ,specially  deoxy ribo nucleic acid , specially deoxy ribo nucleic acid[DNA] and histone protein  The nuceic acid besides being responsible for the physiological and m olecular activities  in the body  also  acts as genetic material .              NUCLEIC ACIDS    ; The nucleic acid are mainly found in the nucleous .They are long chain molecules , built of repeating  small molecules , called  nucleotides , joined end to end  in a chian . They are   not found in  free state but complexed  with the protein to form nucleo protein , the chromatin .The  nucleic acid obtained earlier from  yeast cells was named zymonucleic acid  and that  from the  thymus , the thymo nucleic acid . The nucleic acid are of two types ,the deoxyribose nucleic acid , abbreviated  as dna ,and ribose nucleic acid , abbreviated as rna .The former  is found  in the nucleus, mitochondria  and chloroplasts, whereas the lattewr  is found un nuccleolus and cyto plasm.                                                                                                                                                                   DEOXYRIBOSE NUCLEIC ACID                                                                                                                              The dna is biolgically  most  important and stable  molecule . It exercises extremely superior role in cellular in heritence ,growth an development  in the cell  division   and synthesis of  protiens  and other chemical consituents  of organisms .In fact  it is a reference library  that  contains  infomation  neede by the cell for performing  its activities ; it is associated with all  biological  processes .                                                                                              Miescher [1869]  was the first scientist to seperate the DNA  from the nucleus of the pus cells and named in nuclein.However ,its role in heredity  was  suggested by hertwig [1884] .The name nucleic acid was  proposed by altman [1889] due to its acidic nature and occurrence  in the nucleus. Scientists got more intersted in DNA  after fourth decade of the present  century and  many scientists such as  Boivin ,Roger ,Vendrelly,Ris ,McCarthy , investigated it and  suggests its role in heridity.In 1953 Watson and Crick proposed an acceptable  structural model of the DNA ,commonly known as double helix model, which can  explain the  specificity  and replication  of genes.                                                                                                      Chemical composition of DNA.The DNA is a polymer and its buiding units are called  nucleotide is made of three different molecules ,a pentose  sugar [5-csugar] ,a nitrogenous  base and phosphate In DNA,the sugar is deoxyribose . Four  different  nitrogennous bases occurs in the DNA .They  includre adenine ,guanine ,cytosine and thymine.The adenine and guanine are  purines ,whereas ,the cyto sine and thymine are pyrimidines .In their structure , the purines  [adenine and guanine]  have double  rings , whereas  pyrimidines hav er only single ring .The bases show the presence  of an  amino group ; in cytosine  and adwenine  this group is present at  number 4 position of the first ring  but in thymine and gua nine, these positions are  occupied  by a keto group [co]. At this c1b position ,the deoxy ribose[pentose sugar] joins a  nitrogenous base  to form a nucleoside ; the four bases  form  four  free hydroxyl group of the pentose in a nucleoside to form a nucleotide .Deprnding  on the four different bases , ther are four  kind s of nucleotides in DNA.., deoxycytidilic acid  or deoxy cyti dilate ,containing  cytosine deoxy thymidyclic acid or deoxy guanilate , containing guanine .The linkage  between the pentous sugar and phos phoric acid is called ester linkage . Thus  a nucleotide  is a phosphate  diester  linkages , one at 3' hydroxyl position and other  at 5' hydro xyl position.Infact,a phosphoric acid  molecule helps in joining two nucleosides ;it is joined to carbon atom 3 ' of one deoxyribose and carbon 5' of other.The four nucleotides  join to form a single DNA strand ,i.e., DNA poynuceotide

                                                                                                                

NOMENCLATURE ;THE BINOMIAL NOMENCLATURE

From earliest time ,living things have been given common names by people who live amidst them .These names have continued through ages .Westill  use many of thwese such as pine ,oak blue grass, blue bell, sun flower , buffalo grass, jelly fish ,star fish dog fish .etc But  common names are highly variable ; they vary from country to country  language to language .For example,a small bird which we call gauraiya  in india  and pakistan , is kown  by different  names in different  languages  in different countries ,e.g., house  sparrow in england , pardal in spain, suzune in japan , musch in holland. Common names are variable in the same region ; some people called a bird wood peacker , some call it flicker , some call it golden wing wood peacker and others call it  yellow hammer or high-hole.The common name in a language means a particular living thing if we know that language or if we live in that community in which it is used.In many cases a single name refers  to many plants and animals . for example , the common  name blue bell  is used for dozons of plants  with  blue ,bell shaped flower. Likewise the name black bird refers to crow , cuckoo , raven or rusty black bird.These are confusing  because nosystem was used in choosing them.                                                                                         Besides being confusing many of the name used  in referring to plant and animal are also misleading ; they give wrong impression of plant-animal relation ship because they have no scientific basis.For example ,silverfish is an insect but it gives an impression of a fish which is entirely different from any insect .Likewise,jelly fish and star fish both  not a fish in any respect ,gives impression of a fish .Likewise sea horse is not a horse  but a type of a fish .The above mentioned short comings of the  common nae have  necessitate the naming  of living things  in only one language scientifically .The naming  of living organisms in thic way  removes confusion in one such name  refers to only one living thing .Linnaeus was the first to use  scientific names of plants and animals.The tenth  edition of his book systema naturae  includes such names of many plants and animals . Linnaeus named  a plant or animal in latin langyuage [ the  language of all intellectual of that time ]  by using two words ; the first words refers to a genus [genuric name ] and the second to a species[specific name ] .This way  of naming a living thing  is called binomial nomen clature.The initial of the first word is written or printed  in capital form, whereas  its remaining letters are are written or printd small form.But all letters of the second word are written or printe in small form .But  all letters of the second wor are wriitten  or printed in small form. when a binomial nomen clature is written ,its both  both words are  underlined . In books this nomenclature is printe in italic letters .The binomial nomen clature  is used by biologist  the world all over . It gives  binomial nomen clature  of some familiar  animals .In some  specific cases , atrinomial  nomen clature is used .                                   TRINOMIAL NOMENCLATURE ;Some times , members of species show certain modification  which may be minor but it is quite distinct . Such members are considered as sub species  or  variety of the related species.For species  a trinomial  nomen clature is used .This name  consists of three words; the first words stands for generic name , the second for species name  and the third for sub species name .The modern  man's  trinomial nome clature is  homo sapiens sapiens .Likewise , trinomial nomen clature  of head - louse and body -louse  are pedi cularis  humanus  capitis and  pedicularis humanus  humanus  respectively.                                                                                       

Mimicking Virus Gene Delivery

Thursday August 11, 2011

Influenza Virus Particle Image: CDC/Frederick Murphy

Viruses infect cells by first attaching to their host and then injecting their genome into the host cell. Researchers from the National Physical Laboratory have developed a method for delivering genes inside cells that imitates the way viruses infect cells. It is hoped that this discovery could be used to develop new gene therapy strategies. Gene therapy involves the transplantation of healthy genes into cells to replace missing or defective genes that lead to the development of genetic disorders.
Instead of using a virus vector to transport genes across the cell membrane, the researchers used a peptide sequence named GeT (gene transporter). The cell membrane is a thin semi-permeable membrane that surrounds the cytoplasm of a cell, enclosing its contents. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. The researchers used GeT to enclose the genes and deliver them to the interior of a cell. In the study, GeT was successful in transferring a synthetic gene that coded for a green fluorescent protein to the inside of a cell.acteria Create Food Preservative

Saturday August 6, 2011

Escherichia coli Bacteria Credit: Rocky Mountain Laboratories, NIAID, NIH

Millions of people contract food poisoning each year. Researchers from the University of Minnesota have made an interesting discovery that can help in the fight against food-borne diseases. They have discovered a naturally occurring food preservative that kills dangerous bacteria such as E. coli and salmonella. The preservative, lantibiotic, is produced by harmless bacteria. According to the researchers, lantibiotic is the first natural preservative found to kill gram-negative bacteria. It also kills a wider range of harmful germs than other natural preservatives.
According to the researchers, lantibiotic has several benefits. Not only can it protect meats, eggs, dairy products and canned foods from dangerous bacteria, but it is easily digestible, nontoxic and produces no allergic responses. Another reported benefit is that harmful bacteria have difficulty forming a resistance to it. The researchers have received a patent for lantibiotic and believe that it can be an important tool to protect food from toxic bacteria.