Module 3 Flashcards
Maternal effect
Inheritance pattern for nuclear genes in which the genotype of mother directly determines the phenotype of offspring (due to oogenesis)
(ex. water snail shell)
Epigenetic inheritance
A modification occurs to a nuclear gene/chromosome, altering gene expression and passed from cell to cell
Not permanent, no change to DNA sequence (rather DNA modification via methylation or chromatin structure)
Can occur during gamete formation or embryonic development
Dosage compensation
Meant to offset differences in number of active sex chromosomes, occurs via different mechanisms depending on the species
Barr body
Highly condensed X chromosome in females, example of dosage compensation
Depends on X-inactivation center (Xic) and Xist gene
Function of X-inactivation center
Nucleation: # of Xics is counted, one X chromosome remains active
Spreading: Begins at Xic, inactivation spreads across whole chromosome
Maintenence: Barr body remains through subsequent cell divisions
Genomic imprinting
A segment of DNA is “marked” by methylation, maintained throughout life of organism
Offspring only express one allele
Stages of imprinting
- Establishment of imprint during gametogenesis
- Maintenence of imprint during embryogenesis/in adult somatic cells
- Erasure and reestablishment of imprint in germ cells
Prader-Willi Syndrome (PWS)
Imprinting disease inherited from father, characterized by reduced motor function, obesity, and small hands and feet
Angelman Syndrome (AS)
Imprinting disease inherited from mother, characterized by hyperactivity, thinness, seizures, repetitive symmetrical muscle movements, and mental deficiencies
Extranuclear inheritance
Inheritance patterns involving genetic material outside nucleus (i.e., mitochondrial/chloroplast DNA)
Maternal inheritance
Phenotype solely based on maternal parent mitochondrial genotype
(ex. four o’clock plant leaf color)
Paternal leakage
Paternal parent may occasionally provide mitochondria via sperm
Human ____ diseases occur either from ____ to ____ transmission or mutations in ____ cells (highly susceptible to degenerative diseases)
mitochondrial, mother to offspring, somatic
____ is an important factor in mitochondrial disease
Heteroplasmy
Endosymbiosis theory
Describes evolutionary origin of mitochondria and chloroplasts, endocytosis of bacteria by archaea formed primordial eukaryotes