Lecture 8= 9/27 Flashcards
cytoplasmic inheritance
phenotypes are controlled by nonnuclear genomes found in chloroplasts, mitochondria, infective agents and plasmids. Organelles typically show maternal inheritance.
trait is not in nucleus
maternal effect
: the influences of a mother’s genotype on the phenotype of the offspring.
imprinting
: a process in which gene expression depends on the parent from which the gene came.
Rules of non-Mendelian inheritance of
mtDNA and cpDNA
Ratios typical of Mendelian segregation do not occur because meiotic segregation is not involved.
Reciprocal crosses usually show uniparental inheritance because zygotes receive cytoplasm from the mother.
Paternal leakage occurs at low levels and usually is transient; mechanisms that degrade paternal mtDNA/cpDNA may exist.
chloroplast inheritance
not evenly split, random drift between W+ and mutant
randomized on what chloroplasts are received
syngamous mating
fusion of two equal sized cells
mitochondrial inheritance
Mitochondria are generally maternally inherited
-oocyte cytoplasm to egg transmission
-only females can transmit defected genes to
offspring (in most species)
-both male and female offspring can be affected
- phenotype often related to defect in energy
production.
human mitochondrial genome
Most proteins in mitochondria are imported from cytoplasm
100,000 copies of mitochondrial DNA in ovum
human mitochondrial genome
Most proteins in mitochondria are imported from cytoplasm
100,000 copies of mitochondrial DNA in ovum
segregational petite
nuclear mutation
mendelian inheritance
neutral
lacks most ntDNA
cytoplasmic inheritance
suppressive
mutant mtDNA acts as dominant
cytoplasmic inheritance
mitochondrial inheritance pattern
transmitted from the mother to all the offspring
if father is affected, offspring are fine
The phenotypic effects of mitochondrial mutations
reflect the extent to which a tissue relies on oxidative phosphorylation; the central nervous system is most sensitive, followed by skeletal muscle, heart muscle, kidney, and liver.
Homoplasmy:
the existence of a uniform population of organelles within a cell or an individual
