Video of Chlamydomonas mating sequence
http://bio.rutgers.edu/~gb101/lab6_protists/m6a3b.html
Yeast mating:
(1) Two haploid cells (of opposite mating groups)
(2) The cells grow toward the source of the opposite pheromones
(3) The cells fuse and form diploid
Different forms of isogamy:
(A) isogamy of motile cells
(B) isogamy of non-motile cells
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(C) conjugation
If homogametic (XX)
If heterogametic (XY)
Different forms of isogamy:
Different forms of anisogamy:
(A) isogamy of motile cells
(B) isogamy of non-motile cells
(A) anisogamy of motile cells
(B) oogamy (egg cell and sperm cell)
(C) conjugation
(C) anisogamy of non-motile cells (egg cell and spermatia)
If homogametic (XX)
If heterogametic (XY)
DAX1 (X chromosome) produces
anti-testis factor
SRY gene (sexdetermining region
on Y), inhibits DAX1
induces testes
development
rare recombination
b/w the X and Y
chromosomes
DAX1
SRY
Male (XY)!
X and Y
pair during
meiosis
!
DAX1
SRY
Pseudoautosomal
Regions
(PAR)
Testes are
produced
"
X-bearing
sperm
Male (XY)!
Female (XX)!
Two X’s
pair during
meiosis
Ovaries are
produced
Y-bearing
sperm
Male (XY)!
Female (XX)!
Two X’s
pair during
meiosis
rare recombination
b/w the X and Y
chromosomes
DAX1
SRY
Genotype: XX
(female)!
Male (XY)!
Female (XX)!
Two X’s
pair during
meiosis
rare recombination
b/w the X and Y
chromosomes
DAX1
SRY
DAX1
SRY
Genotype: XX, but with the SRY gene!!!!!!
Genotype: XY (male)!
Male (XY)!
Female (XX)!
Two X’s
pair during
meiosis
Male (XY)!
Female (XX)!
Two X’s
pair during
meiosis
rare recombination
b/w the X and Y
chromosomes
rare recombination
b/w the X and Y
chromosomes
DAX1
SRY
Steroid hormones
•! Produced by gonads, travel through bloodstream
•! Androgens
–! Testosterone, dihydrotestosterone, androstenedione
•! Estrogens
–! Estradiol, estrone, estriol
•! Aromatase converts androgens to estrogens
Aromatase !
Aromatization of testosterone into estradiol
Genotype: XY, but with no SRY gene!!!!!!
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Genotype: XX
(female)!
Genotype: XY
(male)!
Temperature-dependent sex determination in
three reptile species: the American alligator
(Alligator mississippiensis), the red-eared slider
turtle (Trachemys scripta elegans), and the alligator
snapping turtle (Macroclemys temminckii).
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Location-dependent sex
determination Bonellia marine worms
Larvae are free-swimming and are
initially sexually undifferentiated
Those larvae that fall to ocean floor
develop as females (150cm)
Those larvae coming into contact with
established females are masculinized
by exposure to bonellin from females
(males are tiny 2-3mm & live inside
females genital sac & produce sperm)
Location-dependent sex determination in a cluster of Crepidula snails.
Two individuals are changing from male to female. After these molluscs
become female, they will be fertilized by the male above them.
SEX
By Laurence D. Hurst and James P. Randerson
By directing its
victims’ sex lives, the
bacterial parasite
WOLBACHIA may be
helping to produce
new species
Don’t bite the hand that feeds you.
The old adage sums up the approach parasites are expected to take
with their victims. A freeloader that can spread only when its host
reproduces ought not to be overly harmful: too much damage to its
unwilling benefactor will affect the parasite’s own chances to procreate. This scheme contrasts with the tactics of a pathogen that has
a short infectious period, such as the flu virus. In that case, the virus
56
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has no long-term interest in the carrier’s well-being, so a “get transmitted quick” strategy is favored almost regardless of the cost to the
FRANCIS M. JIGGINS
GENDERBASED GENOCIDE:
The bacterium Wolbachia
eliminates male Acraea
encedon butterflies because
only females can serve as
hosts for the parasite and
pass its spawn on to the
next generation.
hapless host.
The widely distributed bacteriumWolbachia (a close relative of the
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