hurry up

• covalent bonding occurs between two or more non-metal elements when they share pairs of valence electrons in order to achieve a full valence shell and become stable
• effects of cystic fibrosis: produce excessive mucus, sweat and digestive juices in the lungs, causing difficulty breathing
• mutation for CF is found on chromosome 7 and is known as the ‘cystic fibrosis transmembrane conductance regulator’ (CFTR) gene. The CFTR gene helps move salt in and out of your cells. In CF, the movement of salt doesn’t happen properly
• independent assortment: random arrangement of homologous chromosomes during meiosis which results in new combinations of alleles in the gametes
• fertilisation: mixes the DNA of two parents when genetically unique gametes from each parent join together to form a zygote
• natural selection pt 1: genetic variation exists in a population
• natural selection pt 2: some phenotypes may be better suited to the environment
• natural selection pt 3: individuals with better suited phenotypes will survive and reproduce passing on their favourable alleles to their offspring
• naturla selection pt 4: over generations the frequency of favourable alleles increases in the population this increases the chances of survival of the species
• selective breeding: choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics
• mutation cause: exposure to mutagens eg certain chemicals or radiation or by an error in the replication of DNA just before a cell divides
• ionic bonding occurs when oppositely charged ions form an electrostatic force of attraction through the transfer of valence electrons between ions in order to achieve a full valence shell and become stable