Lecture 28 Flashcards
what is cytoplasmic inheritance?
when sperm fertilizes egg, offspring inherits many things from mother thru oocyte cytoplasm
what does the offspring inherit from oocyte cytoplasm? (3)
- proteins
- mRNAs
- organelles
2 other names for cytoplasmic inheritance
- maternal inheritance
- extranuclear inheritance
where do offpsring acquire their mitochondria?
from the mother
describe the mt genome?
> 16,000 nt circular DNA
how many mt are in a cell? what does each have?
dozens-hundreds of mt per cell, each with multiple mtDNA copies
what % of cellular DNA is made of mtDNA
1%
what does mtDNA encode? is this cytoplasmic or mendelian inheritance?
mtDNA encodes 13 proteins and 24 rRNAs/tRNAs –> CYTOPLASMIC INHERITANCE
the proteins that mtDNA itself encodes are involved in what?
involved in ETC
how many proteins are in a mt?
> 1000
if mt only encodes 13 proteins, how are there >1000 proteins in mt?
encoded in nuclear genome: produced in cytoplasm then imported to nucleus
3 factors that affect mt genome replication
- many mtDNA are replicated within nucleoids
- nucleoids divide within a mt
- mt divide within a cell
what is a nucleoid?
protein particle that holds mtDNA
how does mtDNA relate to nuclear DNA?
INDEPENDENT
how many mitochondria are in oocyte vs sperm?
oocyte: >100,000 mt
sperm: ~100 mt
if sperm have mt, why are mt only inherited from the oocyte?
upon fertilization, all sperm mt are destroyed/consumed by oocyte via autophagy
why are mt DNA are helpful research tool?
can be used as a tool to trace maternal heritage
what is poky gene?
slow growth mutant when mutation in mtDNA –> maternally inherited
what is ad gene?
nuclear gene –> mendelian inheritance
what are the offspring if poky female with ad+ is crossed with WT male with ad-?
poky is maternally inherited, half offspring are ad+, half are ad-
what are the offspring if WT female with ad- is crossed with poky male with ad+?
poky cannot be inherited bc in male, so they are WT with half ad+ and half ad-
is maternal inheritance independent or dependent of mendelian inheritance?
maternal inheritance is INDEPENDENT of mendelian inheritance
rate of mutation in mt genes vs nuclear genes
mt genes have 1000x greater mutation rate than nuclear genes
2 reasons why mt genes have greater mutation rate than nuclear genes
- more frequent DNA replication
- no DNA repair
what is heteroplasmy?
spontaneous mtDNA mutations can make WT and mutant mt populations in a cell
what is homoplasmy?
cell has only WT or mutant mt population
what proportion of ppl have disease caused by mt dysfunction?
1/5000 people
describe diseases caused by mt dysfunction
progressive and multi-system diseases
describe the 2 possible causes of mt dysfunction diseases
- some are autosomally inherited
- some are due to mtDNA mutation
will children of an affected mother have mt disease? why?
ALL children of affected mother will have disease bc of maternal inheritance
(but if mother heteroplasmic, children may be normal)
will children of an affected father have mt disease?
children of affected father will NEVER have disease
how to prevent mt disease with 3-parent fertilization?
offspring has mother’s nuclear material and donor’s mt material
