Non-Mendelian Inheritance Flashcards
What is extranuclear inheritance?
Genomes from other organelles that can be passed on to the offspring, namely mitochondrial DNA and chloroplast DNA
What is a maternal effect?
When maternally contributed RNA determines the phenotype of the offspring regardless of the progeny genotype
If a gene is found in the mitochondria, what determines the genotype and phenotype of the offspring?
The genotype and phenotype of the mother. Male gametes don’t have mitochondria or chloroplasts but the egg cells do, so all mitochondrial DNA will be the same as the mother and so will the phenotype
What treatment can be used to avoid passing on a mitochondrial disease from parent to offspring?
Three-parent in vitro fertilization, using a pronuclear transfer. The nucleus of a fertilized egg of the patient is put into an egg with WT mitochondria from a donor
Where is the RNA coming from when we have a maternal effect?
Nurse cells of the mother
What determines the phenotype of the progeny when there is a maternal effect?
The genotype of the mother
What is epigenetic inheritance?
Inheritance not determined by the DNA sequence
What two things cause epigenetic inheritance?
Methylation and histone modifications
What effect does methylation have on gene expression?
It is repressed, RNA polymerase can’t bind
What is imprinting?
When a segment of DNA gets marked during meiosis, and that mark is retained so the offspring doesn’t show the phenotype of that allele
What are the 3 steps in imprinting?
- Gametogenesis: producing the gametes and establishing the imprint
- Maintenance of the imprint during embryonic development: that allele continues to not be expressed
- Reassure and reestablishment: the imprint gets erased in the germ line cells and then put back on when that organism makes gametes
Which allele will determine the phenotype of the offspring if it is paternally imprinted?
The allele inherited from the mother
Which allele will determine the phenotype of the offspring if it is maternally imprinted?
The allele inherited from the father
How is Prader-Wili syndrome inherited?
It is maternally imprinted, and offspring that inherit the mutant chromosome 15 with the deletion from their father will have the disorder
How is Angelman syndrome inherited?
It is paternally imprinted and the affected offspring only expresses the maternal chromosome 15 with a small deletion
