Transcript SexDetermination_posted

Review Question
Is it possible for a male cat to be a
tortoiseshell?
Sex Determination in
Drosophila and other
organisms
X chromosome: Autosome
Balance
In Drosophila, sex is determined by the ratio of
the number of X chromosomes to the number of
sets of autosomes
Genetic sex
determination
systems vary
Other kinds of sex determination
•
•
•
•
•
•
Grasshoppers, crickets, roaches: XO
Nematodes: ______
Bees, ants, wasps: haplodiploidy
Many Snakes: _______
Lizards: both XX/XY and ZZ/ZW systems
Crocodiles, most turtles, and some lizards, sex is
determined by the incubation temperature during
a critical period of embryo development. This is
known as ____________________________.
Temperature Dependent Sex
Determination
In some animals, sex is not
‘determined’ at all!
Some fish change sex as they get
older or larger. In clown fish,
largest group member is ______,
second largest is _______, and
all others are ______________.
Sometimes the largest fish in the
group will become ______, all
others will be ______ (wrasses).
Coral Goby
Gobiodon histrio
Monogamous pairs
If mate dies or
leaves, resident
will____________
_______________
_______________.
And some species are all female
Cnemidophorus uniparens
are all female; reproduce
via _________________.
Diploid or triploid eggs develop directly from oocytes
(___________________), no cellular/nuclear division.
At meiosis, identical rather than homologous
chromosomes pair, and then segregate.
All offspring are females and ____________________
__________________________________.
Cnemidophorus species tend to have extremely low
levels of genetic diversity.
Plants
• Hermaphrodite flowers
• Hermaphrodite and
male flowers on the
same plant
• Male and Female
flowers on the same
plant
• Male and Female
flowers on different
plants
Genomic Imprinting
Differential expression of alleles at a locus depending
on whether the allele has been inherited from the
mother or the father.
Disease can result from imprinting
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Paternal SNRPN
gene active-Maternal SNRPN
Paternal SNRPN
paternally imprinted
Gene inactive by
Gene inactive by
(chrom. 15)
imprinting
mutation
Fertilization
Mild retardation
Compulsive
eating
Obesity
Diabetes
Prader-Willi
Syndrome
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Both copies
inactive
A nearby gene (also on chrom.
15) is maternally imprinted
• A mutation in this gene results in
Angelman Syndrome: mild retardation,
seizures, and involuntary muscle
contractions.
• Which parent is the mutant allele inherited
from in Angelman’s Syndrome?