how many chromosomes do humans have cell

Since the bacterial cell is prokaryotic, a true nucleus is absent. The nuclear material is represented by DNA which is not associated with histones. It is identified as a nucleoid or bacterial chromosome . It is a circular ring. It is attached at a point to the plasma membra..

Heredity depends upon the protoplasmic continuity between the parent and the offspring. It is the gametes that establish the continuity between parent and offspring and hence, the mechanism of inheritance operates across this exceedingly slender protoplasmic bridge. The machinery of inheritance lie..

With the rediscovery of Mendelism, several scientists focussed on identifying the basis for inheritance. William Sutton recognised a close parallelism between the transmission of 'factors' identified by Mendel and the behaviour of chromosomes during meiosis and fertilization. These ideas ..

Circulatory System - The transport system in animals is called the circulatory system. The materials are transported from one part of the body to another by a mass flow system which is the circulatory system. The animals, particularly the more advanced forms, have a higher metabolic rate. This mean..

The eye lens converges these light rays to form a real, inverted and diminished image on the retina. The light sensitive cells of the retina gets activated with the incidence of light and generate electric signal..

The closed circulatory system can be represented as follows. Diagram showing inter-relationship between artery, vein and capillary The closed blood vascular system is a very well developed system This is so because, a) The organisms have a thick body wall to prevent the evaporation of water, so exc..

In human beings, sexual reproduction takes place. Sexes are separate and hence they are known to exhibit sexual dimporphism. Males have sex organs called the tetes while the females have sex organs called the ovaries. Even in the external appearance, males and females show differences. So..

Three types of cells are found suspended in the plasma of blood. They are: erythrocytes (RBC), leukocytes (WBC) and thrombocytes (Platelets). Erythrocytes (red blood corpuscles) are spherical or oval cells that are responsible for the oxygen carrying capacity of blood. The RBC a..

Summary - 1) The human body has elaborate mechanisms for protection against foreign bodies, germs and cancer cells. 2) Immunity is either innate or acquired. 3) Innate or non-specific immunity refers to a wide variety of body responses against a wide range of pathogens. 4) Previ..

Largest cell organelle, enclosed by an envelope of two membranes that is perforated by nuclear pores. It contains chromatin which is the extended form taken by chromosomes during interphase. It also contains a nucleolu..