Chapter 1 : recombinant DNA technology

 Introduction To facilitate the study of genes, they must be isolated and amplified. One method of isolation and amplification of a gene of interest is to clone the gene by inserting it into another DNA molecule that serves as a vehicle or vector that can be replicated in living cells. When these two DNAs of […]

Chapter 2 : the chemical composition of DNA

DNA is a polymer ( a large molecule that contains repeating units) composed of 2’ deoxyribose (a five-carbon sugar), phosphoric acid, and the four nitrogen containing bases denoted A, T, G and C. The chemical structures of the bases are shown below. Note that two of the bases have a double-ring structure, these are called […]

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, […]

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. […]