Genetic Inheritance

• A gamete is a sex cell. Gametes differ from normal cells as they contain half the number of chromosomes found in other body cells.
• Chromosomes are thin strands of DNA. They are subdivided into genes.
• A gene is a section of DNA which controls part of a cell's chemistry, particularly protein synthesis.
• Alleles are different versions of the same gene.
• A dominant allele is always expressed, even if one copy is present. Dominant alleles are represented by a capital letter.
• A recessive allele is only expressed if the individual has two copies and does not have the dominant allele of that gene
• Homozygous alleles are both identical for the same characteristic. Homozygous refers to having inherited the same alleles of a genomic marker from each biological parent.
• Heterozygous is where alleles are both different for the same characteristic.
• A genotype is the combination of alleles that a person has for a particular trait
• A phenotype is the physical characteristics of an organism
• Some characteristics are controlled by a single gene, such as fur colour in mice, and red-green colour blindness in humans.
• Each gene may have different forms, called alleles
• The alleles present, or genotype, operate at a molecular level to develop characteristics that can be expressed as a phenotype
• A dominant allele is always expressed, even if only one copy is present
• A recessive allele is only expressed if two copies are present (therefore nor dominant allele is present)
• If the two alleles present are the same , the organism is homozygous for that trait, but if they are different they are heterozygous
• Most characteristics are the result of multiple genes interacting rather than a single gene