Genetic inheritance

• An allele is a different version of the same gene.
• A genotype is the combination of alleles that have been inherited.
• A phenotype is the observable impact of the genotype.
• Homozygous is when both genes in the genotype are the same.
• Heterozygous is when both genes in the genotype are different.
• Inherited disorders are caused by faulty genes, which are mostly recessive alleles. This means two genes need to be present for them to be expressed. An individual that carries just one recessive gene for an inherited disease is known as a carrier.
• Some inherited diseases are caused by dominant allele. The presence of one of these alleles will cause the disease to be expressed and seen in the phenotype.
• Genetic screening involves analysis of a persons' DNA to see if they carry alleles that cause genetic disorders.