Relative Masses Atomic Mass Unit The mass of a single atom is so small that it is impossible to weigh it directly Atomic masses are therefore defined in terms of a standard atom which is called the...
Structure of an Atom All matter is composed of atoms, which are the smallest parts of an element that can take place in chemical reactions Atoms are mostly made up of empty space around a very smal...
Recombinant DNA Technology Recombinant DNA The genetic code is universal, meaning that almost every organism uses the same four nitrogenous bases – A, T, C & G. There are a few exceptions The g...
Genome Sequencing Projects A genome contains all of the genes within an organism Advances in technology have allowed scientists to map and sequence the genes within an organism's genome Genome sequ...
Totipotent Cells A stem cell is a cell that can divide (by mitosis) an unlimited number of times Each new cell that is produced when a stem cell divides has the potential to remain a stem cell or t...
Gene Mutations A gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide Mutations occur continuously and spontaneously Errors in the DNA...
The Definition of a Community Species do not exist by themselves in their own isolated environment, they interact with other species forming communities A community can be defined as: Multiple popu...
Edexcel IGCSE Maths复习笔记 1.9.1 Compound Interest What is compound interest? Compound interest is where interest is paid on the interest from the year (or whatever time frame is being used) befor...
What is a reverse percentage? A reverse percentage question is one where we are given the value after a percentage increase or decrease and asked to find the value before the change How to do rever...
