Inheritance in Genetic Disease Flashcards
(24 cards)
What is the definition of genotype?
The set of genes that an organism carries, responsible for a particular trait.
What is the definition of phenotype?
The physical expression of a trait, influenced by genotype, environmental factors, and lifestyle choices.
What are alleles?
Different forms of the same gene, with sequence variations between them.
What is gene dosage?
The number of copies of a gene present in a cell, typically two in diploid organisms.
What is a single gene disorder?
A genetic disorder caused by an abnormality in a specific gene.
Give examples of single gene disorders.
- Cystic Fibrosis
- Sickle cell disease
- Fragile X
- Duchenne Muscular Dystrophy
- Huntington disease
- Tay-Sachs disease
- Polycystic kidney disease
What is a dominant allele?
An allele that shows a phenotypic effect even if the individual has only one copy.
What is a recessive allele?
An allele that does not show a phenotypic effect if the individual has only one copy.
What is penetrance?
The proportion of individuals with a particular genotype that express the associated phenotype.
What is expressivity?
The degree to which the phenotype is displayed between different individuals.
What is complete dominance?
Where the effect of one allele completely masks the effect of the other in a heterozygous genotype.
How is the inheritance pattern of autosomal dominant alleles characterized?
Affected individuals are found in each generation, and both genders are affected equally.
What effect does incomplete penetrance have on inheritance patterns?
Some individuals may not display a disease phenotype despite having the dominant disease genotype.
What is the inheritance pattern of autosomal recessive alleles?
25% affected offspring from two carrier parents, 50% unaffected carrier offspring, and 25% unaffected offspring.
What is the typical characteristic of autosomal recessive disease phenotypes in families?
They appear and leave suddenly, often skipping generations.
What is the inheritance pattern of X-linked alleles?
100% affected sons, no affected daughters; daughters are carriers.
What is the inheritance pattern of Y-linked alleles?
100% affected sons, no daughters affected.
What is the inheritance pattern of mitochondrial diseases?
Maternally inherited.
What is anticipation in genetics?
A phenomenon where the phenotype of a dominant condition becomes more severe or develops earlier with each generation.
What is a de novo mutation?
A mutation that occurs for the first time in an individual without a family history of the disorder.
What is allelic heterogeneity?
The presence of multiple alleles at a particular locus that lead to the same phenotype.
What is locus heterogeneity?
When mutations at different loci cause the same disease phenotype.
What are the allele frequencies used to calculate disease risks?
Where p + q = 1; p is the frequency of the normal allele, q is the frequency of the abnormal allele.
What is the risk of an unaffected offspring being a carrier if both parents are heterozygous carriers?
67% chance of being a carrier.
