SEX DETERMINATION
 Many groups use sex chromosomes to determine sex.
Mammals have the X and Y chromosomes
 XX = female, XY = male
 Sex of mammals is determined by the Y chromosome. In
the absence of Y, gonads become ovaries.
 All other chromosomes are called “autosomes” Thus,
humans have 46 chromosomes, 44 autosomes plus 2 sex
chromosomes.
X and Y Chromosomes
 The X has many genes on it, just like the autosomes. Most





of the genes on the X have nothing to do with sex.
The Y has very few genes on it. It consists of mostly
inactive DNA.
One gene on the Y is very important: SRY. The SRY gene is
the primary determinant of sex.
If SRY is present, testes develop in the early embryo. The
testes secrete the hormone testosterone, which causes
development as a male.
If SRY is absent (no Y chromosome), ovaries develop
instead of testes, and the embryo develops into a female.
The X and Y chromosomes share a common region at their
tips, the pseudoautosomal region. Crossing over in meiosis
occurs in this region.
Sex Chromosomes in Other Organisms
1. Sex chromosome composition in birds, butterflies, moths and
some fish is opposite that of mammals, with the male the
homogametic sex (ZZ) and the female heterogametic (ZW).
Z-linked genes behave like X-linked genes in mammals, but
the sexes are reversed.
2. In plants, the arrangement of sex organs varies:
a.Dioecious species (e.g., ginkgo) have plants of separate
sexes, one with male parts, the other with female.
b.Monoecious species have male and female parts on the
same plant.
i. Perfect flowers have both types of parts in the same
flower.
ii. Imperfect flowers (e.g., corn) have male and female
parts in different flowers on the same plant.
3. Some dioecious plants have sex chromosomes and use an Xchromosome-autosome balance system, but many other sex
determination systems also occur in dioecious plants.
Chapter 11 slide 4
KONTROL PENAMPILAN SEX
Penyerbukan pada tumbuhan
penyerbukan silang (alogami)
penyerbukan sendiri (autogami).
Tipe sex pada tumbuhan
Pada individu bunga:
1. Staminat atau Androecious: bunga hanya mempunyai stamen atau
benang sari saja, dan disebut bunga jantan
2. Pistilat atau Ginoecious: bunga hanya mempunyai karpel atau putik saja
dan disebut bunga betina
3. Hermaprodit atau Sempurna: bunga mempunyai stamen dan karpel
4. Neuter or Agamous: bunga tanpa stamen dan karpel atau organ sex
abortive
Pada individu tumbuhan
1. Androecious: pada satu tanaman hanya ada bunga jantan
2. Ginoecious: pada satu tanaman hanya ada bunga betina
3. Monoecious: pada satu tanaman terdapat bunga jantan dan bunga
betina pada bunga yang berbeda
4. Hermaprodit: pada satu tanaman hanya ada bunga hermaprodit
5. Andromonoecious: Pada satu tanaman terdapat bunga jantan dan
bunga hermaprodit
6. Ginomonoecious: pada satu tanaman terdapat bunga betina dan
bunga hermaprodit
7. Trimonoecious: pada satu tanaman selain terdapat bunga jantan dan
bunga betina juga terdapat bunga sempurna
Pada populasi tumbuhan
1. Monoecious: suatu populasi
tumbuhan yang terdiri dari
hanya tumbuhan monoecious
2. Dioecious: suatu populasi
tumbuhan yang terdiri dari
hanya tumbuhan androecious
dan ginoecious
3. Hermaprodit: Suatu populasi
tumbuhan yang terdiri dari
hanya tumbuhan hermaprodit
Kromosom sex pada tumbuhan
Silene latifolia
- tumbuhan jantan memiliki kromosom sex heteromorfik
XY (22 kromosom, kromosom sex XY)
- tanaman betina terdapat 22 kromosom dan kromosom sex
XX.
Rumex sub genus acetosa
- rasio (banyaknya kromosom X/banyaknya set autosom) sama dengan 1.0
maka terjadi tumbuhan ginoecious.
- jika rasionya 0.5 atau lebih kecil maka terjadi tumbuhan androecious
- jika antara 0.5 dan 1.0 maka akan dijumpai tumbuhan andromonoecious,
hermaprodit, atau ginomonoecious.
Tanaman dioecious asparagus (Asparagus officinalis).
- Yang jantan memiliki kromosom sex heteromorfik.
- YY dijumpai hidup dan fertil.
Cannabis sativa
- tipe sex heterogametik XY monoecious
- homogametik XX menampilkan ginoecious.
Alel resesif pada kromosom X mengurangi kemampuan menjadi
betina
-tanaman XXm menampilkan tipe sex dari ginoecious sampai ke
monoecious
-tanaman XmXm menjadi tanaman jantan dengan morfologi
bunga seperti bunga betina
Gen Mendelian Yang Mengontrol Tipe Seks
Penampilan seks pada ketimun
Genotipe
M_F_
M_ff
mmF_
mmff
Fenotipe
Ginoesious
Monoesious
Hermaprodit
Andromonoesious
Penampilan seks pada melon
Genotipe
A_G_
A_gg
aaG_
aagg
Fenotipe
Monoesious
Ginomonoesious
Andromonoesious
Hermaprodit
Penentuan sex secara molekuler
Dengan menggunakan teknik PCR (Polymerase Chain Reaction) dimana
fragment DNA dapat diamplifikasi secara in vitro, identifikasi sex pada
tanaman dapat dilakukan
PCR tanaman Salix viminalis
PCR Silene latifolia.
(no 5-8 = tanaman jantan)
The search for sex-specific markers in Leucadendron :
Applications of ISSR and suppression subtractive hybridisation
All species Leucadendron are dioecious
Karyotyping
RAPD
ISSR
could not identify sex chromosomes
25 RAPD primers could not identify sex-specific
markers for 12 Leucadendron species
37 primers and 8 combined primers failed to find
sex-specific fragment
Plants with heteromorphic sex chromosomes
Silene latifolia, 64 RAPD primers
identified 4 male-specific markers
Canabis sativa, 15 RAPD primers
found 2 male-specific markers
Silene latifolia
SCAR marker
No heteromorphic sex chromosomes
Ginko biloba, 1200 RAPD primers detected 1 male-linked band
Pistacia vera, 1000 primers, 1 sex marker found
P. atlantica, 472 primers, 1 sex marker identified
Leucadendron?
♂
45 ISSR primers
could not
identify sexspecific
fragments
1000bp
750bp
500bp
♀
Male substracted library
B
194
217
1500bp
1000bp
700bp
500bp
Differential screening of male substraction
(A) Probed with ♂
(B) Probed with ♀
Insert
no
Approx
size
(bp)a
Clear
readable
sequence
Accession no
2
3
600
710
220
725
AJ627251
AY586361
11
500
272
AJ428413
17
30
101
470
450
1000
463
252
321
Z00044554304
AY582139
U63020
197
620
617
AJ428413
204
510
321
BAA22288
220
680
680
AJ428413
240
510
503
AJ970307
354
620
639
AJ428413
356
620
639
AJ428413
362
650
662
AJ428413
Gene(s)
cpDNA 23S rRNA
cpDNA
NADH
dehydrogenase subunit
F
cpDNA rpoC2
cpDNA rrn23
cpDNA psaB
cpDNA D1 protein
(psbA)
cpDNA petB and petD
polyprotein
(mat_peptides)
cpDNA
ycf6-psbM
intergenic spacer
cpDNA16S rRNA and
tRNA Ile
cpDNA 23S rRNA and
tRNA Ala
cpDNA 23S rRNA and
tRNA Ala
cpDNA tRNA Ile and
tRNA Ala
Organism
Sequence
identity
E-value
Nymphaea alba
Fagus grandifolia
182/188 (96%)
466/477 (97%)
1e-88
0.0
Calycanthus fertilis
var. ferax
Nicotiana tabacum
Panax ginseng
Magnolia
pyramidata
Calycanthus fertilis
var. ferax
Oryza australiensis
213/229 (93%)
4e-86
429/438 (97%
228/239 (95%)
284/309 (91%)
0.0
7e-103
1e-108
543/593 (91%)
0.0
88/106 (83%)
2e-37
Calycanthus fertilis
var. ferax
104/121 (85%)
62/70 (88%)
55/66 (83%)
466/477 (97%)
2e-19
2e-10
600/609 (98%)
0.0
601/612 (98%)
0.0
336/347(96%)
5e-168
Cucumis sativus
Calycanthus fertilis
var. ferax
Calycanthus fertilis
var. ferax
Calycanthus fertilis
var. ferax
0.0
the male and female genome might be rather
homologous
the non-recombining region in Leucadendron is
very small
chloroplast copy number may differentiate male
and female L. discolor