BIOL 461 Lecture Notes - Lecture 25: Mating Type, Chlamydomonas, Y Chromosome
29 Apr 2018
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BIOL 461 – LECTURE 25 – make up day
Uniparental or Cytoplasmic Inheritance
- Rules of inheritance were totally violated
Maternal effect phenotype
- Not talking about a maternal EFFECT
o Mother is mutant, looks WT but her progeny are
mutant
o Mother has to provide a gene product
o If the mother is homozygous mutant then all of
her progeny will be mutant
- Male should be mutant
- If the ale laks the gee, the the progey are WT eause its ot the ale does’t proide it
to the egg
- Cytoplasmic inheritance
o The traits / mutant phenotype is always transmitted
from one gender (female usually) aka uni-parental
o If one individual is mutant in a cross, then all of the
progeny will show that mutant phenotype
o Mutant phenotype is always transmitted from one
gender of a cross!!!!! In this case maternal
o Any time the female is mutant all the progeny will get
it BUT if the male has the mutant phenotype the
progeny will not get the mutant phenotype
- Different from maternal effect, where the male can be
transmitting the allele for that trait
- Materal iheritae it’s alays trasitted fro oe geder
Chlamyodomonas Reinhardtii
- Unicellular
- Eukaryotic green alga
- Haploid
- Chloroplast
- Flagella
- Yeast like model organism
- Life cycle: normally live as haploid,
but then if they become starved
for nitrogen, then the 2 types of
cells that are + or -, will
differentiate into gametes
- The whole cell will differentiation into a gamete – ready for mating
- Then those + and – cells will go from uniform looking the same cells, to specialized cell types for
mating, in which the plus cell will mate only with minus cells
find more resources at oneclass.com
find more resources at oneclass.com
2
- sometimes form big aggregates, interact with flagella because they have sticky proteins on their
flagella that oly iterat ith the opposite atig type’s flagella
- They’ll fuse, take off ell all
- Make diploids, that have 4 falgella (briefly)
- Diplodis can grow as dipoids indefinitely
- Diploids will hang around in a survival capsule, and when
oditios get etter they’ll udergo eiosis ad ake a e
meiotic/haploid population
- Plants have, in their chloroplasts, have their own genome
- Makes protein of the choloroplast photosynthesis apparatus
- The chloroplasts have their own genetic system, their own
riosoes, RNApol…..
- Have their own genome because they have evolved from a
photosynthetic bacterium
- Retaied their geeti systes, ee though they’re a
organelle now
- Our mitochondria is a similar storey
Linkage groups of the
chromosomes of Chlamydomonas
- One locus – the mating type
locus
- Ursula Godoenough discovered
- Instead of having a Y chromosome to determine gender, they
have a locus, (mating type locus) which can either have genes for
being a plus cell or being a minus cell.
- One gene determines mating type
- No gene conversion, but analogous to MAT locus
- If they’re plus they have set of genes at this one location in chromosome (A or 8?) that makes
them plus, or different ones that make them minus
- What happens with the chalmy chloroplast genome:
o Has a uleus, the ulear geoe = 7 hroosoes, ut e’re
just indicating if that genome is plus or minus (grey circle)
o Plus and minus will mate
o Their chloroplasts have these red spots (genome of the chloroplast)
o They’ll ate ad ake a diploid, ad the this protei alled Ezy-1,
encoded by the plus genomes mating type locus, which goes in to
the chloroplast, expressed within 30 mins, and then degrades the
chloroplast genome that was acquired from the mating type minus cell
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Biol 461 lecture 25 make up day. Not talking about a maternal effect: mother is mutant, looks wt but her progeny are mutant, mother has to provide a gene product. If the mother is homozygous mutant then all of her progeny will be mutant. If the (cid:373)ale la(cid:272)ks the ge(cid:374)e, the(cid:374) the proge(cid:374)y are wt (cid:271)e(cid:272)ause its (cid:374)ot the (cid:373)ale does(cid:374)"t pro(cid:448)ide it to the egg. Cytoplasmic inheritance: the traits / mutant phenotype is always transmitted from one gender (female usually) aka uni-parental. If one individual is mutant in a cross, then all of the progeny will show that mutant phenotype: mutant phenotype is always transmitted from one gender of a cross!!!!! In this case maternal: any time the female is mutant all the progeny will get it but if the male has the mutant phenotype the progeny will not get the mutant phenotype. Different from maternal effect, where the male can be transmitting the allele for that trait.
