Mendelian inheritance and single gene diseases Flashcards
What are central examples of monogenic disorders?
Examples include Cystic fibrosis, Tay-Sachs disease, and Sickle cell anemia.
These disorders are caused by mutations in a single gene.
What are the different patterns of Mendelian inheritance?
- Recessive
- Dominant
- X-linked
These patterns describe how traits and diseases are passed from parents to offspring.
What is the law of segregation in Mendelian inheritance?
Alleles of the same gene separate when gametes are produced during meiosis.
This was formulated by Gregor Mendel.
What is the law of independent assortment?
Alleles are assorted independently of each other, except for linked alleles.
This applies to genes located on different chromosomes.
What is the difference between dominant and recessive inheritance?
Dominant inheritance is expressed in individuals with one allele, while recessive inheritance is expressed with two alleles.
Dominant traits appear in every generation, whereas recessive traits may skip generations.
What is a pedigree?
A family tree used to determine inheritance patterns in monogenic diseases.
Pedigrees help visualize the transmission of traits through generations.
What are the characteristics of X-linked recessive inheritance?
- Mainly affects males
- No father-to-son transmission
- Heterozygote females may be unaffected or mildly affected
Examples include Duchenne muscular dystrophy and hemophilia.
What is genomic imprinting?
A gene is only expressed if inherited from one parent, leading to one allele being expressed in cells.
An example is Angelman syndrome.
What are unstable repeat expansion diseases?
Diseases caused by mutations that change from generation to generation, often leading to anticipation.
Examples include Huntington disease and Myotonic dystrophy.
What is the difference between homoplasmy and heteroplasmy in mitochondrial inheritance?
- Homoplasmy: pure population of normal or mutant mtDNA
- Heteroplasmy: both normal and mutant mtDNA present
This affects the expressivity and severity of mitochondrial diseases.
What is penetrance?
The proportion of individuals with a specific genotype that express the associated phenotype.
It can be complete or reduced, leading to skipped generations in some disorders.
What is expressivity?
The severity or degree of expression of a phenotype among individuals with the same genotype.
Variable expressivity can result in different symptoms even among family members.
What role does consanguinity play in genetic disorders?
Increases the frequency of recessive disorders due to shared ancestry.
Example: Tay-Sachs disease is more common in Ashkenazi Jews.
What is mosaicism?
Presence of at least two genetically different cell lines in an individual or tissue.
Example: Segmental neurofibromatosis type 1.
What is the inheritance pattern for autosomal dominant disorders?
50% chance to inherit the mutated gene.
Examples include Huntington disease and Marfan syndrome.
X-linked recessive inheritance
No father-to-son transmission.
Affected males cannot pass the trait directly to their sons because sons inherit their father’s Y chromosome, not the X.
Genetic causes of mitochondrial diseases
Mutations in
* mitochondrial tRNA/rRNA genes
* or oxidative phosphorylation (OXPHOS) genes in mtDNA
* and in nuclear genes encoding mitochondrial proteins.
Most show maternal inheritance, but nuclear mutations can follow autosomal recessive or dominant patterns.
True or False: X-linked dominant traits can be inherited from father to son.
False
X-linked dominant traits do not have male-to-male transmission.
What is the significance of the CFTR gene?
It is associated with cystic fibrosis, a common autosomal recessive disorder.
Over 2000 different mutations can occur in this gene.
Achondroplasia inheritance pattern?
Autosomal dominant
Achondroplasia is a common form of genetic dwarfism. homozygote do not survive the new-
born period
What is the probability that a child of two parents with achondroplasia will also have achondroplasia?
25%
Each child of two parents with achondroplasia has a 25% chance of inheriting the disease.
What is the inheritance pattern discussed in the context of achondroplasia?
Autosomal dominant
Achondroplasia follows an autosomal dominant inheritance pattern.
