Definitions + Misc. Flashcards
Congenital
A condition or anomaly present at birth.
Hereditary
Refers to conditions that are genetically transmitted from parents to offspring.
Familial
Refers to conditions that “cluster” in families and can include genetic as well as nongenetic (e.g. ADHD, HTN) conditions.
Genotype
The genetic makeup of an individual, or different forms of a gene at a given locus on a chromosome.
Phenotype
The observed expression (physical, biochemical, or physiological) of a genotype.
Penetrance
The ability of a known disease-causing genotype to exhibit the disease phenotype.
Describe the penetrance for a condition in which 10% of the population with the disease-causing genotype do not go on to develop the disease.
The penetrance in this situation would be 90%.
Variable expressivity
When individuals who have the same genetic condition/genotype have varying degrees of the associated phenotype.
Genomic Imprinting
Imprinting turns of selected genes, so the expression of the gene depends on whether the gene was inherited from the mother or the father.
Pleiotropic
Refers to genes that produce many effects. An example is Marfan syndrome, which can affect the eyes, cardiovascular system, and skeletal system.
Mosaicism
The presence of ≥2 genetically different sets of cells in the same person caused by an error in mitosis.
Heterozygous
Refers to the presence of two different alleles at a gene locus on a pair of homologous chromosomes.
Homozygous
Refers to the presence of two identical alleles at a gene locus on a pair of homologous chromosomes.
Autosome
Refers to all chromosomes except the X and Y chromosomes.
Nondisjunction
Occurs when homologous chromosomes or chromatids fail to separate, resulting in an abnormal number of chromosomes in the daughter cells.
Aneuploidy
Refers to the presence of an abnormal number of chromosomes in a cell.
Complex
Anomalies of several different structures that are near each other during embryonic development (ex: limb-body wall complex)
Association
Anomalies seen together that do not have a known single genetic or developmental etiology (ex: VACTERL)
Syndrome
A recognizable pattern of structural defects, due to a known single genetic etiology, with a predictable natural history that remains relatively consistent across unrelated patients (ex: Cornelia de Lange, Williams)
Balanced Translocation
An even exchange of genetic material between chromosomes, resulting in no extra or missing genes.
Unbalanced Translocation
An uneven exchange of genetic material between chromosomes, resulting in extra or missing genes.
Sequence
A pattern of multiple anomalies caused by a single identifiable even in development (ex: Pierre Robin sequence)
What is multifactorial inheritance?
Genetic disorders which are due to multiple genetic and environmental factors rather than a “single gene” mutation.
What (7) factors suggest multifactorial inheritance has occurred?
There is no discernable Mendelian inheritance pattern; recurrence risk increases as the number of affected individuals in the family increases; recurrence risk is higher if the affected individual is a member of the less commonly affected sex; recurrence risk is higher if the individual has a more severe form/case; recurrence risk drops dramatically as the degree of familial relationship decreases from the affected individual; recurrence risk correlates with the prevalence in the general population; and environmental factors play a role.
Are dizygotic twins more likely, less likely, or equally likely to have genetic traits similar to those of a nontwin sibling?
From a straightforward genetic perspective, dizygotic twins are no more similar than nontwin siblings.
Name 4 diseases or abnormalities that are more likely to be concordant in monozygotic than dizygotic twins.
Autism (60% vs 0%), Cleft lip/palate (38% vs 8%), clubfoot (32% vs 3%), and spina bifida (72% vs 33%).
