What is a stem cell? Ultimately, every cell in the human body can be traced back to a fertilized egg that came into existence from the union of egg and sperm. But the body is made up of over hundreds of different types of cells. All of these cell types come from a pool of […]
Author: Dr ABDOLMOHAMMADI AKBAR
Leçon 2 : futur simple
Le futur simple se forme du verbe à l’infinitif + -ai, -as, -a, -ons, -ez, ont. les verbes réguliers en –er : Donner je donnerai […]
lesson 1: Present continuous
Study this example situation: I’m working.please be quiet.This mean: I’m working now, at the time of speaking.The action is not finished. Am/is/are + –ing is the present continuous: I am doing something = I’m in the middle of doing it, I’ve started doing it and I haven’t finished: The weather is nice at the moment […]
Chapter 11 : specific features of meiosis
Meiosis has three unique features : The mechanism of cell division varies in important details in different organism. This is particularly true of chromosomal separation mechanism, which differ substantially in protists and fungi from the process in plants and animals that we will describe here. Meiosis in a diploid organism consists of two rounds of […]
Chapter 10 : meiosis
The sequence of events during meiosis involves two nuclear divisions ( meiosis I and meiosis II ). Prophase 1 In prophase 1 of meiosis, the DNA coils tighter, and individual chromosomes first become visible under the light microscope as a matrix of fine threads. Because the DNA has already replicated before the onset of meiosis, […]
Leçon 1 : le présent
Le présent de l’indicatif est utilisé pour : 1) Exprimer un fait qui se déroule au moment où on le rapporte : -je mange mon sandwich. – J’écris une lettre. – Je conduis ma voiture. 2) Exprimer une action qui dure : – tu étudies le français depuis un mois. – tu habites à Bruxelles depuis […]
Chapter 9 : Replication
1) Definition The DNA replication is one of the key mechanisms of cell cycle. It is a highly regulated biological process in which new synthesis and repair mechanisms ensure the integrity of the genome. S phase or replication phase follows the G1 phase during which the cell synthesizes all the elements necessary for this replication. […]
Chapter 5 : exercices and exam questions (probability)
Problem 1: A marketing survey indicates that 60% of the population owns an automobile, 30% owns a house, and 20% owns both an automobile and house. Calculate the probability that a person chosen at random owns an automobile or a house, but not both. (A) 0.4 (B) 0.5 (C) 0.6 (D) 07 (E) 09 Problem […]
Chapter2: torque and angular momentum in circular motion
Definitions: the torque and angular momentum are defined as vector products of position, force and momentum. Suppose a forceacts on a particle whose position with respect to the origin 0 is the displacement vector . Then the torque “about the point 0 and acting on the particle,” is defined as: Now suppose the particle has […]
Chapter 1: uniform circular motion
When an object has a circular motion even though its speed is constant, it is nonetheless accelerating because according to newton’s 1st law: an object continues in its state of rest or uniform motion unless acted on by an external force. So if the object was to be free in space then of course it will […]