Genes and Alleles

Basic Understanding of Genes and Alleles

• Genes are segments of DNA that code for a specific trait or function in an organism.
• Each gene holds the information needed to produce proteins, which carry out the majority of the work within cells and are necessary for the structure, function, and regulation of the body’s tissues and organs.
• An allele is one of two or more versions of a gene; each person inherits two alleles for each gene, one from each parent.
• The alleles can be identical (homozygous) or different (heterozygous).

Concepts of Dominant and Recessive Alleles

• Alleles can be dominant or recessive, which affects how they determine traits.
• Dominant alleles show their effect even if there is only one copy of that allele (i.e., they dominate the corresponding recessive allele).
• Recessive alleles only show their effect if both copies are the same, in other words, if the individual is homozygous for that recessive allele.

Role of Alleles in Genetic Diversity

• The multiplication of alleles contributes greatly to genetic diversity and evolution, as they allow for different variations of the same characteristic.
• Genes undergo mutation, leading to the creation of new alleles, bringing about genetic diversity in populations.
• Through sexual reproduction and the process of meiosis, these varied alleles are shuffled and recombined, ensuring a diverse range of traits in offspring.

Genes, Alleles, and Genetic Disorders

• Certain combinations of alleles can lead to genetic disorders.
• Genetic disorders can be monogenic, meaning they are caused by mutation in a single gene; examples include cystic fibrosis and sickle cell anaemia.
• Genetic disorders can also be polygenic, meaning many genes (along with environmental factors) contribute to the disorder; examples include heart disease and type 2 diabetes.