Genetics is the science of understanding the relationship between heredity, diseases and physical traits. Its focus is on genes, their pattern of transmission and their connection to traits and diseases. Inherited diseases are fairly prevalent. Therefore, access to a glossary of genetic terms is an important tool for health literacy in this area. Such knowledge can improve your understanding of your health and your health care. Additionally, it is food for thought in planning a family.
Allele – Is one of several alternate forms of a gene in a specific location on a specific chromosome that encodes one of the variations of a trait or disease. In medical terms, alleles determine the nuances of a phenotype. Humans and many other types of organisms inherit two different alleles for a given phenotype – one from each parent. One is usually dominant and the other is recessive. Eye color is an example. The gene for blue eyes and the gene for brown eyes are alleles of the eye color locus on its proper chromosome.
Autosome – Is one of the 22 pairs of chromosomes that determine traits other than gender. They exist as pairs in humans because we receive a set from each parent. We also have a pair of sex chromosomes which determine gender and sexual traits. They are labeled X and Y for females and males respectively. The pair is XX for a female. It is XY for a male.
– Autosomal – adj.
Autosomal dominance – Is the reference to the determining of a disease or physical trait by the transmission of a gene for it from only one parent to the offspring. The gene must also be on a chromosome not encoding sex traits.
– Autosomal dominant – adj.
Autosomal recessive – Is the descriptor for a pattern of inheritance in which both parents must transmit the gene that causes a physical trait or disease in order for it to be present in their offspring. It thus denotes that in order for a given phenotype to exist there must be two copies of the gene for it – one from each parent. In the same vein, a recessive gene must be homozygous to express itself as a phenotype.
Chromosome – Is one of the threadlike linear structures within the nucleus of all nucleus-bearing cells of humans and other forms of life. It contains the genetic code for their physical traits. It is composed of DNA and each is the residence for a specific set of genes. Humans have a total of 46. Lower forms of life have fewer.
Dominant – Pertaining to the expressing gene of a heterozygous pair and the masking of the other gene. It denotes the gene that dictates the phenotype.
Gene – Is a segment of DNA on a chromosome which bears the code for a given physical trait or disease. It is the fundamental unit of heredity.
Gene mutation – Is a permanent alteration of a gene resulting in a disease or unusual phenotype. The alteration is in the DNA sequence of a chromosome. It can be hereditary or acquired. A de novo mutation is an alteration in a gene that is not hereditary. It presents for the first time in a family member as a result of a genetic change which occurs in the sperm or egg of one of the parents or in the fertilized egg that becomes the fetus. Mutant – adj.
Genome – Is the full set of chromosomes determining all of the physical traits of a person or other organism.
Heterozygous – Possessing two different alleles on corresponding gene loci from both parents. The expressed one is dominant. It determines a trait or presence of disease. The unexpressed allele is recessive or silent.
– Heterozygosity – n.
Recessive – Pertaining to the dormancy of a gene as a result of its masking by a dominant gene.
Sex linked – Pertaining to the transmission of a trait or disease to an offspring as a result of a gene(s) on the X or Y sex chromosome of a parent(s). It differs from autosomal.