mating in filamentous ascomycota Flashcards
a typical ascus contains
8 ascospores
operculum
at the tip of the ascus where the spores are released from
what controls the mating process of Saccharomyces cerevisiae
a complex genetic locus called MAT at which two linked genes are located
which two linked genes are located at MAT a complex genetic locus which controls mating in Saccharomyces cerevisiae
a1,a2 for mating type a and alpha 1 and alpha2 for mating type alpha
MATa locus encodes for
a1 and a2 polypeptides, the messengers for which are transcribed in opposite direction.
a and alpha
join to produce a zygote from two septette ascomycota
- in one ascomycota there will be genes for a and in others gene for alpha
basidiomycetes have..
thousands of sexes
name some of the sexes of basidiomycetes
Homothalic (self fertile), heterthalic (partner required), monjaryon (uninucleate haploid), homokaryon (uni-or multi-nucleate haploid (n)_, dikaryon ( binucleate haploid (n+n)), heaterokaryon (multinucleate (n +n)), diploid (2n).
homothallic
self fetile
heterothallic
sex requires a partner
monjarygon
uninucleate haploid
homokaryon
uni or multi nucleate haploid (n)
dikaryon
binucleate haploid (n+n)
heterokaryon
multinucleate (n+n)
diploid
2n
for mating to be successful in basidiomycetes ..
all sexes HAVE TO BE DIFFERENT
how many diff sexes in Schizophyllum
28,000
what maintain dikaryon
clamp connections
- ensuring that every hyphal compartment within a mycelium is binucleate
where are basiospores produced
on basidia
sexual reproduction in Zygomycota
1) +ve and -ve mycelia make contact
2) gametangia with haploid nuclei and then plasmogamy
3) a young zygosporgangium (heterokaryotic) forms
5) the zygosporangia goes through karygoamy to produce a diploid nucleus
6) meiosis
7) forms into a sporangium
8) spore get released from sporangium and these spore are dispersed and germinate mycelia
mycelia reproduction can either be..
asexual or sexual
- e.g. the spore produced my mycelia can either be used to germinate itself or other mycelia
sexual reproduction in Ascomycota
1) +ve ascogonium and -ve ascogonium make contact
2) plasmogamy
3) DNA shared
3) an ascocarp is formed with ascus’ that are dikaryotic
4) karygamy–> forms a diploid nucleus (zygote)
5) meisois- four haploid nuclei
6) mitosis- eight ascospore
7) ascospore dispera
8) germinate mycelia
sexual reproduction in ascomycota can be
sexual or asexual
yeast can reproduce asexually by
budding
sexual reproduction in Basidiomycota
1) positive and negative mating type
2) plasmogamy
3) dikaryotic mycelium is formed
4) gills of fungi lined with basidia which are dikaryotic
5) karyogamy- forming a diploid nuclei
6) meiosis
7) basidium containing four haploid nuclei dispersed as basidiospore
8) germination of haploid mycelia
dikaryon/heterokaryons are established through ……. mating
SOMATOGAMOUS
plasmogamy
is a stage in the sexual reproduction of fungi, in which the cytoplasm of two parent cells (usually from the mycelia) fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell.
karyogamy
is the final step in the process of fusing together two haploid eukaryotic cells, and refers specifically to the fusion of the two nuclei. Before karyogamy, each haploid cell has one complete copy of the organism’s genome.
basidiospore are produced on
basidia
in basidomycota spore discharge is
passive or mediated by bullers drop
bipolar heterothallism
one mating-type gene,w with two alleles (e.g. A and a) are compatible. However A xA or a xa are incompatible (homogenise incompatibility)
tetrapolar heterothallism
two mating types genes with two or more alleles (e.g.A and a with B and b). only combinations that differs at all four alleles are fully compatible e.g. AB x ab.
secondary hoothallism
in some bipolar heterothallic species, spore can form that segregate both mating-types together. the mycelium is consequently self fertile.
outcrossing
mating between different haploid strain
outcrossing can either be
outbreeding or inbreeding
outbreeding
mating between different haploid strains from different spore sources (non sib)
inbreeding
mating between different haploid strains from the same spore source (sib)
non-outcrossing
self mating between identical haploid strains
outcrossing strategies require the opening up of
‘self’ to ‘non-self’ genetic info which can lead to cooperatives, mergers, takeovers and STDs
