M1: Sex Determination Flashcards
Basis of Sex Determination in an Organism
Genes and Sex Autosomes
Females have two X chromosome and Males have one X chromosome. Unequal chromosome number, female have more sex chromosome
Protenor System (XX/XO)
Basis for Protenor System
Protenor Butterfly
Equal chromosome number and most famous sex determination
Lygaeus System (XX/XY)
Characteristics of Male in Lygaeus System
- Heterogametic
- Unlike Gametes
- Heteromorphic Chromosomes
- Determines sex of progeny
Characteristics of Female in Lygaeus System
- Homogametic
- Like Gametes
- Homomorphic Chromosomes
Opposite of Lygaeus System and females dictate the sex of pyrogeny
ZW system (ZZ/ZW)
Females are diploid and Males are haploid
Haplo-Diplo System
Neither male nor female intervenes and need to find haploid alleles
X Chromosomes: Haploid Number
A threshold for maleness is reached when the X:A ratio is 1:2
Genic Balance Theory
Ratio of X chromosomes: 1.0 - 1.5
Female
Ratio of X chromosomes: 0.67 - 0.75
Intersex
Ratio of X chromosomes: 0.33 - 0.50
Male
Incubation temperature of eggs during a critical period of embryonic development
Temperature Variation
Houses the genetic information necessary for maleness and trigger gonodal ridge development into ovaries or testes
Y chromosome in Humans