Biology (Medical Entrance)

Down's syndrome or mongolism or mongolian idiocy is caused by the trisomy on chromosome number 21. Thus, the egg possesses 24 chromosomes instead of 23 and the offspring has 47 chromosomes (45 + XY in male, 45 + XX in female). 

F. Sanger was the first person to work out the complete amino acid sequences of insulin and got the Nobel Prize in 1958. Insulin is a protein of 51 amino acids. It is made up of two polypeptide chains held together by disulphide bridges. 

Phytoplankton produce their required sugar through photosynthesis. As they are able to produce their own energy with the help of light, they are considered autotrophic (self-feeding). Phytoplankton and other autotrophs are called primary producers, and make up the bottom of the food web.

The technique which makes use of amniotic fluid for the detection of gentic disorders is called amniocentesis. This process involves the removal of some amniotic fluid form around the foetus by means of slender needle inserted throguh the abdomen of the mother. It is used throuhg the abdomen of the mother. It is used to detect any hereditary disease in embryo. 

The theory where ratio between the number of X-chromosomes and number of complete sets of autosomes will determine the sex is known as genic balance theory of sex determination. The X-chromosome is believed to carry female tendency genes, while autosomes carry male tendency genes.

Gastrulation is the dynamic process involving critical changes in the embryo, such as differentiation of cells, establishment of the three primary germ layers and transformation of a single walled blastulla into a double walled gastrulla. During involution or emboly, the insinking endodermal cells migrate anteriorwards along the roof of blastocoel and give a new cavity called gastrocoel or archenteron. It represents the future gut cavity. Blastocoel formed during Blastulla stage is filled with an alkaline albuminous fluid secreted by surrounding micromeres.

The condition of chromosomal change which involve the loss or gain of single chromosome is called aneuploidy. Genotype 22 pairs + XXY males shows the condition of Klinefelter's syndrome. Klinefelter's syndrome was studied in 1942 by an American Dr. H.F. Klinefelter. The patient of this syndrome have an extra X chromosome, hence the genotype is XXY instead of normal XY and patient has 47 chromosomes instead of 46. 

During ageing, decrease in calcium content of arteries and cartilage takes place. The study of ageing is known as Gerontology. 

Binomial nomenclature, introduced by Carolus Linnaeus is the method of naming an organism with the genus name first and species name later.

Sir Alec Jefferys (1885-86) first developed DNA fingerprinting technology. 

To obtain 200 sperms, 100 secondary spermatocytes are required as 1 secondary spermatocyte produces 2 sperms.

 The chromosomes as thread like structures in nucleus was first described by E. Strasburger in 1975. These thread like structure were called chromosomes (chroma = colour) due to their affinity for basic dyes.

One the main reasons that pandas have become endangered is habitat destruction.Due to the fact that pandas reproduce so infrequently, it is very difficult for their population to recover from such a low point.

Homologous organs are similar in structure and origin but not necessarily in function. Hence, organs from different species having a similar basic form, microscopic structures, body positions and embryonic development are said to be homologous. Homologous structures showing adaptations to different environmental conditions and modes of life are examples of adaptive radiation.
<span style="font-family:" arial;="" font-size:="" 10pt;="">The fossils of prehuman and ancestral human forms are obtained form widely diverse regions of Africa, Asia and Europe, which indicates that man's center of origin was probably in Asia and <st1:place w:st="on" style="font-family:" arial;="" font-size:="" 10pt;="">Africa<span style="font-family:" arial;="" font-size:="" 10pt;="">. More precisely man has originated in central Asia because the number of domesticated animals and plants is maximum in Asia and the oldest known fossils have been obtained from Asia, China, Java and India. Climatic conditions in Asia and nearby places were most conductive for human evolution.

Vitamin C is needed for the growth and repair of tissues in all parts of your body. It is used to:
1.Form an important protein used to make skin, tendons, ligaments, and blood vessels
2. Heal wounds and form scar tissue
3.Repair and maintain cartilage, bones, and teeth
4. Aid in the absorption of iron

Vitamin K, calcium ions and fibrinogen play a significant role in blood coagulation, but vitamin D has no role in blood coagulation. 

Haeckel (1986) proposed, “the theory of recapitulation” or “Biogenetic law” which states that an individual organism in its development (Ontogeny) tends to repeat the stages passed through by its ancestors (phylogeny) i.e., “Ontogeny repeats phylogeny”. 

Sterilisation in woman is done by blocking the passage of ova in fallopian tubes either by cutting or by ligaturing these tubes. This is called tubectomy or salpingectomy. It is a major and complicated operation because the fallopian tubes are deeply located in the addomen.<o:p>
Sterllisation of man is done by Vasectomy in which the passage of sperms is blocked either by cutting or by putting ligatores around the vase deferenta. <o:p>Castration or orchidectomy is the removal of testes. It produce eunuchs and changes aggressiveness of male into docile nature. 

The carrier of heredietary metarial is gene. It is a functional unit of heredietary material. The term gene was proposed in 1909 for the first time by Johannsen. Gene's is also the smallest unit that could undergo a mutational change or could take part in recombination. 

Peripatus is a connecting between arthropods and annelids. 

Huxley is the founder of neo systematics.It includes description of all the characters (internal) including morphological characters (external) of plants or living organism.

Variations are the initiation force of evolution. Variations are difference among individuals of a group or species. That can be ascribed to age, sex or position in the life cycle. 

Factor VIII is known as antihaemophilic globin factor (AHG or AHF). It remains absent in the patients suffering from haemophilia. 

The queen normally lives for about 5 years and does nothing except laying eggs. She possesses immensely developed ovaries, a large abdomen and a body which is nearly five time larger and about three times heavier than that of worker.