Genetics

• Meiosis is a type of cell division. It's different to mitosis because it doesn't produce identical cells. In humans, meiosis only happens in the reproductive organs.
• Before the cell starts to divide, it duplicates it's DNA. One arm of each X-shaped chromosomes is an exact copy of the other arm.
• DNA strands are polymers made up of lots of repeating units called nucleotides.
• Each nucleotide consists of one sugar molecule, one phosphate and one base
• The sugar and phosphate molecules in the nucleotide form a backbone to the DNA strands. The sugar and phosphate molecules alternate.
• A DNA molecule has two strands coiled together in the shape of a double helix.
• The complementary base pairs are joined together by weak hydrogen bonds.
• A gene is a section of DNA on a chromosomes that codes for a particular protein.
• The DNA starts to come out of the strawberry solution because it is not soluble in cold alcohol. It will appear as stringy white precipitate that can be fished out with a glass rod.
• The membrane in the extraction of DNA experiment is broken down using detergent and the salt will make the DNA stick together.
• Different genes control different characteristics. Some characteristics are controlled by a single gene.
• All genes exist in different versions called alleles.
• You have two versions of every gene in your body - one of each chromosome in a pair.
• Homozygous trait


  An organism has two alleles for a particular gene that are the same.
• Heterozygous trait


  Two alleles for a particular gene are different.
• Your genotype is the combination of alleles you have.
• The inheritance of a single characteristics is called monohybrid inheritance. You can use a monohybrid cross to show how recessive and dominant traits for a single characteristic are inherited.
• There are 23 matched pairs of chromosomes in every human body cell.
• Genetic variation within a species is caused by organisms having different alleles which can lead to differences in phenotype.
• Genetic variation can be caused by new alleles arising through mutations.
• Variation within a species can also be caused by the environment.
• Mutations are changes to the base sequence of DNA. When they occur within a gene they result in an allele.
• Some mutations have a small effect on the phenotype.
• Very rarely, a single mutation will have a big effect on phenotype. For example, it might result in the production of a protein that is so different that it can no longer carry out its function. This is what happens in cystic fibrosis. A mutation causes a protein that controls the movement of salt and water into and out of cells to stop working properly. This leads to the production of thick, sticky mucus in the lungs and digestive system. which can make it difficult to breathe and digest food.
• The Human Genome Project started in 1990 and was completed in 2003z
• The Human Genome Project has helped to identify 1800 genes related to disease.
• Genome research has highlighted some common genetic variations between people.
• Increased stress


  If someone knew from an early age that they are susceptible to a nasty brain disease they could panic every time they get a headache.
• Gene-ism


  People with genetic problems could come under pressure not have children.
• Discrimination by employers and insurers


  Life insurance could become impossible to get if you have any genetic likelihood of serious disease and employers may discriminate against people who are genetically likely to get a disease.