1. I. Allelic, Genic, and Environmental Interactions
II. Sex Determination and Sex Linkage

2. I. Allelic, Genic, and Environmental Interactions
II. Sex Determination and Sex Linkage
A. Sex Determination
Environmental Sex Determination
a. Temperature
MT FT

3. I. Allelic, Genic, and Environmental Interactions
II. Sex Determination and Sex Linkage
A. Sex Determination
Environmental Sex Determination
a. Temperature
MT FT

4. I. Allelic, Genic, and Environmental Interactions
II. Sex Determination and Sex Linkage
A. Sex Determination
Environmental Sex Determination
a. Temperature
MT FT

5. I. Allelic, Genic, and Environmental Interactions
II. Sex Determination and Sex Linkage
A. Sex Determination
Environmental Sex Determination
a. Temperature
Winter Melon (Benincasa hispida)
- flowers begin as perfect in bud
- male or female parts aborted as flower develops… monoecious plants with separate male and female flowers
- at lower temps, ratio of Abcissic/Indole Acetic Acid declines – influences development = more female flowers
(Huang et al. 2012, Grubben 2004)

6. “Jack-in-the-Pulpit”
A. Sex Determination
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
Arisaema triphyllum
“Jack-in-the-Pulpit”
Small plants - male
Large plants - female

7. Benefit of being male – quantity of offspring
A. Sex Determination
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
Benefit of being male – quantity of offspring
Benefit of being female – regulate quality of offspring
Cervus elaphus
Red deer
Starving pregnant females selectively abort male embryos. Small daughters may still mate; small sons will not acquire a harem and will not mate. Selection has favored females who save their energy, abort male embryos when starving, and maybe live to reproduce next year.

8. Sexually mature female
A. Sex Determination
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Sexually mature female
(Inhibits development of males)
Sexually mature male
Immature males
Wouldn’t the species do better if there were more females/group?
Yes, but selection favors individual reproductive success.

9. A. Sex Determination Midas cichlid Brood
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Brood

10. A. Sex Determination Midas cichlid Add Larger juveniles Brood female
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Add Larger juveniles
Brood
female

11. A. Sex Determination Midas cichlid Add smaller juveniles Brood male
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
Midas cichlid
Add smaller juveniles
Brood
male

12. ts homozygotes – tassle develops female flowers
A. Sex Determination
Environmental Sex Determination
a. Temperature
b. Size/Nutrition
c. Social Environment
These are still undoubtedly GENETIC effects, likely caused by the activation of different genes under different conditions. MUTATIONS in single genes can influence sex determination.
ts homozygotes – tassle develops female flowers
At other loci:
sk (silkless)
ba (barren stalk)
No female flowers in silk
But these loci that influence sex are not all on the same chromosome.

13. The presence of 1 or 2 sex chromosomes determines sex
A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
The presence of 1 or 2 sex chromosomes determines sex
Order: Hemiptera “True Bugs”
Family Alydidae – Broad-headed bugs

14. The type of sex chromosomes determines sex
A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
The type of sex chromosomes determines sex
Order: Hemiptera
Family: Lygaeidae “Chinch/Seed Bugs”

15. Which sex is the ‘heterogametic’ sex varies
A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
Which sex is the ‘heterogametic’ sex varies
XX female, XY – male
Most mammals, including humans
Some insects
Some plants
ZZ male, ZW female
Birds
Some fish
Some reptiles
Some insects (Butterflies/Moths)
Some plants

16. The ratio of X’s to autosomal sets determines sex
A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
c. Balanced sex determination
The ratio of X’s to autosomal sets determines sex
Human genotype and sex
2n: , XX = female
2n: , XY =male
2n+1: 47, XXY = male
2n-1: 45, X = female
Have a Y = male
No Y = female
Drosophila genotype and sex
2n: , XX =female
2n: , XY = male
2n+1: 9, XXY = female
2n-1: 7, X = male
Ratio of autosomal sets:X = 2:1 = male
Ratio of autosomal sets:X = 1:1 = female

17. A. Sex Determination Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
c. Balanced sex determination
d. Human sex determination: SRY gene

18. A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
c. Balanced sex determination
d. Human sex determination: SRY gene
The presence of the Y, regardless of the number of X’s, determines maleness
Klinefelter’s Male
Turner’s Female

19. A. Sex Determination
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
c. Balanced sex determination
d. Human sex determination: SRY gene
SRY gene produces the protein called the testis determining factor, which stimulates the undifferentiated gonadal tissue to become a testis. It is a transcription factor that binds to other genes, stimulating their expression.

20. A. Sex Determination X X* X*X male Y- XY- female
Environmental Sex Determination
Chromosomal Sex Determination
a. Protenor sex determination
b. Lygaeus sex determination
c. Balanced sex determination
d. Human sex determination: SRY gene X X*
X*X male Y-
XY- female

21. A X A Y a X AaXX AaXY a X a Y A X Aa XX Aa XY Sex Determination
Sex Linkage: Genes of interest are one of the sex chromosomes (X or Y)
1. For Comparison –heredity for sex (as a trait) and an autosomal dominant trait (A,a).
Autosomal genes NECESSARILY assort independently from sex-linked genes
RECIPROCAL CROSSES
MALE: AAXY
FEMALE: aa XX
A X
A Y
a X
AaXX
AaXY
MALE: aa XY
FEMALE:
AA XX
a X
a Y
A X
Aa XX
Aa XY
All offspring, regardless of sex, express the A trait in both reciprocal crosses

22. Xg Y XG XGXg XGY XG Y Xg XGXg XgY Sex Determination Sex Linkage
1. For Comparison –heredity for sex (as a trait) and an autosomal dominant trait.
2. Sex Linkage example: red-green coloblindness in humans
MALE
FEMALE Xg Y XG
XGXg
XGY
MALE
FEMALE XG Y Xg
XGXg
XgY
100% G, for all offspring 50% G daughters, 50% g sons
Now, the sex of the parent that expresses the G trait matters; the transmission of this gene correlates with the sex of the offspring, because this trait and ‘sex’ are influenced by the same chromosome.

23. Queen Victoria of England
Her daughter Alice
X-linked recessive traits are expressed in males more than females, because females get a second X that may carry the dominant allele.

24. Sex Determination
Sex Linkage
Dosage Compensation
- Females have two ‘doses’ of X-linked genes, while males have one ‘dose’. Since protein concentration is often important in protein function, how is this imbalance corrected?

25. Sex Determination
Sex Linkage
Dosage Compensation
- Females have two ‘doses’ of X-linked genes, while males have one ‘dose’. Since protein concentration is often important in protein function, how is this imbalance corrected? In females, one X in each cell condenses.
Barr Body

26. Sex Determination
Sex Linkage
Dosage Compensation
Actually, in all humans and mammals, all but one X condenses, regardless of sex or number of X’s.

27. Sex Determination
Sex Linkage
Dosage Compensation
Random X-inactivation leads to tortoiseshell heterozygote females

28. Sex Determination
Sex Linkage
Dosage Compensation
Calico determined by a different autosomal gene that affects rate of melanocyte migration to the skin surface.
Melanocytes
XBXb, pp
No migration of melanocytes to skin
White
Slow migration
Calico
XBXb, Pp
Inactivation before proliferation
Fast migration
XBXb,PP
Torty
Proliferation before inactivation

29. Sex Determination
Sex Linkage
Dosage Compensation
This happens in humans, too – so that females are really a ‘mosaic’, with some cells in a tissue expressing one X (and it’s X linked traits) and some cells in that tissue expressing the other X. Females heterozygous for red-green colorblindness have patches of retinal cells that can’t distinguish red from green.

30. Anhidrotic ectodermal dysplasia