Patterns of Inheritance and Sex Determination Flashcards
What are the 4 simple gene trait inheritance patterns?
Autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive
What are autosomes?
Chromosomes that are not the sex chromosomes, so everything except X and Y
How do we differentiate between autosomal and sex linked inheritance?
Do a reciprocal cross
What is a reciprocal cross?
A cross in which the phenotypes of each sex are reversed. Ex. if the original cross was AA female x aa male, the reciprocal cross would be aa female x AA male
What sort of patterns are seen in the F1 and F2 for a monohybrid cross for an autosomal gene? What about the reciprocal cross?
All the F1 will have the dominant trait, and the F2 will be a 3:1 ratio. The reciprocal cross will be exactly the same
What sort of patterns are seen in the F1 and F2 for a monohybrid cross for an sex-linked gene? What about the reciprocal cross? (Say the original cross was AA female x aa male)
Original cross: all F1 will have the dominant trait. F2 will have the 3:1 ratio, but only the males will have the recessive trait.
Reciprocal cross: all the F1 females will have the dominant trait, all the F1 males will have the recessive trait. The F2 will have a 1:1:1:1 ratio with 25% dominant females, 25% recessive females, 25% dominant males, 25% recessive males
What two things should be looked for to determine if a gene is sex linked?
If any of the F1 have the recessive trait, or if only the males have the recessive trait in the F2
How do the X and Y chromosomes form a bivalent?
They have a pseudoautosomal region that allows them to recognize each other and form a bivalent during meiosis
What patterns will a gene in the pseudoautosomal region of the X chromosome show?
The same patterns as an autosomal gene
What are the 4 ways that sex can be determined in an organism?
Sex chromosomes, haplodiploid system, environmental, social dominance
How do sex chromosomes determine sex?
Homogametic and heterogametic sex. One sex has two copy of the same sex chromosome, the other sex has the one copy and then something else. This is found in mammals and some insects (XX is female, XY is male or XX is female and X is male for grasshoppers), and birds (ZZ is male, ZX is female)
How does the haplodiploid system determine sex?
The sex is determined by the ploidy of the individual. Males are haploid and are from unfertilized eggs and females are diploid and are from fertilized eggs. This is found in ants and bees
How does the environment determine sex?
Sex is determined by the temperature that the eggs were incubated at. This is found in reptiles and fish
How does social dominance determine sex?
This is found in clownfish. When the dominant female within a group dies, the dominant male changes sex and becomes the new dominant female
Why do all four systems work in determining sex?
The different sexes result from differences in gene expression
