Moving to the nucleus ..... Biased transmission of alleles or entire chromosomes Segregation distortion (meiotic drive, selfish DNA) Gametophytic effects in plants Biased or unusual patterns of gene expression Maternal effect genes Imprinted genes (parent-of- origin expression bias) Paramutation (allelic cross- talk & silencing)
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Moving to the nucleus..... Biased transmission of alleles or entire chromosomes Segregation distortion (meiotic drive, selfish DNA) Gametophytic effects.
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Moving to the nucleus .....
Biased transmission of alleles or entire chromosomes
Segregation distortion (meiotic drive, selfish DNA)Gametophytic effects in plants
Sperm carrying the SD+ chromosome fail due to chromosomes behaving badly•Fail to replace histone with sperm specific prolamine•Fail to condense as appropriate for a sperm nucleus
SD = duplicated, variant RanGTPase activating protein (RanGAP)•Enzymatically active•Mis-localized to the nucleus (vs. cytosol)•RanGTPase functions: nuclear transport, cell cycle regulation
Rsp is a noncoding “satellite” 120 bp DNA repeat •Peri-cedntric region•Rsp-i 50 copies •Rsp-s 500-700 copies
Any alteration of meiosis or subsequent production of gametes that results in the biased transmission of a particular genotype
Most bias due to post-meiotic events during gametogenesis
Most systems act through heterozygous males, but female systems are known
Other examples:t chromosome of mice: + sperm of t/+ males do not swim > excess of fertilization by t sperm X-linked drivers in drosophila: Y sperm of XY males do not function > excess of female progeny
X-linked drivers in Silene latifolia XY males: Y pollen do not function > excess of female progeny
(Mosher & Melnyk Trends Plant Sci 15:204)
Transmission bias - gametophytic effects in plants
meiotic drive - any alteration of meiosis or subsequent production of gametes that results in the biased transmission of a particular genotype
Genetic mutations that disrupt function of the haploid gametophyte (embryo sac or pollen grain)•Failed gamete production•Sex-specific transmission bias against the mutation
1N1N
(Mosher & Melnyk Trends Plant Sci 15:204)
Transmission bias - gametophytic effects in plants
meiotic drive - any alteration of meiosis or subsequent production of gametes that results in the biased transmission of a particular genotype
Genetic mutations that disrupt function of the haploid gametophyte (embryo sac or pollen grain)•Failed gamete production•Sex-specific transmission bias against the mutation
mutation block
1N1N
[Lalanne et al. Genetics 167:1975]
Transmission bias - gametophytic effects in plants
e.g. seth6 mutation disrupts pollen tube growth in Arabidopsis:
Pollen of + / + plant:All four tetrad
members function4 pollen tubes are
germinating
Pollen of + / seth6 plant:
Only + tetrad (2/4) members germinate
seth6 pollen fails to germinate
e.g. seth6 mutation disrupts pollen tube growth in Arabidopsis:
Organism / gene
♀ genotype
♂ genotype
progeny genotype
Arabidopsis
seth6
pollen function
+ / seth6 + / + + / + 463
+ / seth6 428
+ / + + / seth6 + / + 463
+ / seth6 5
+ / seth6 + / seth6 What is expected here?
Transmission bias - gametophytic effects in plants