Heredity, Gene Regulation, and Development I. Mendel's Contributions II. Meiosis and the Chromosomal Theory III. Allelic, Genic, and Environmental Interactions IV. Sex Determination and Sex Linkage

Heredity, Gene Regulation, and Development I. Mendel's Contributions II. Meiosis and the Chromosomal Theory III. Allelic, Genic, and Environmental Interactions IV. Sex Determination and Sex Linkage A. Sex Determination Environmental Sex Determination a. Temperature MT FT

Heredity, Gene Regulation, and Development I. Mendel's Contributions II. Meiosis and the Chromosomal Theory III. Allelic, Genic, and Environmental Interactions IV. Sex Determination and Sex Linkage A. Sex Determination Environmental Sex Determination a. Temperature MT FT

“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

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.

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.

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

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

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”

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

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: 46, XX = female 2n: 46, XY =male 2n+1: 47, XXY = male 2n-1: 45, X = female Have a Y = male No Y = female Drosophila genotype and sex 2n: 8, XX =female 2n: 8, 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

Sex Determination Gender ‘Gender’ is a role or behavior that a human society correlates with a sex Behavior: wear make-up and a skirt Modern USA Society: Gender = woman Medieval Scotland, modern Wodaabe: Gender = man

Sex Determination Gender ‘Gender’ is a role or behavior that a human society correlates with a sex Sexual Behavior: like most behaviors, a given sexual behavior is not necessarily restricted to one sex or another. And sex is used for more than procreation; it is used for communication, conflict resolution, deception, and establishing dominance within and between sexes. Female Bonobo chimps (Pan paniscus) ‘sneaker’ male

A X A Y a X AaXX AaXY a X a Y A X Aa XX Aa XY Sex Determination Gender Sex Linkage 1. For Comparison –heredity for sex (as a trait) and an autosomal dominant trait. 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

Xg Y XG XGXg XGY XG Y Xg XGXg XgY Sex Determination Gender 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.

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.