Bio Ch 15 Chromosomal Basis of Inheritance

1902- walter suflon propoes that genes are on x'somes
-based on observatons
1. homolog pairs separate during meiosis
2. alleles get segregated during gamete formation (mendel)
3. Also knew that fertilization restored the paired condition for genes & xsomes
-theodore boveri made similar observations

Alleles of genes on nonhomologus xsomes assort independently

2 alleles for each gene separate during gamete formation

Law of independent assortment & law of segregation

First to experimentally show that genes are on xsomes
-0isolated a white eyed mutant\-first to correlate mutation w/ location on xsome
-showed genes are on xsomes! (studied fruit flies)

In f2 only male had white eyes..fly eye color is related to sex of fly..sex linked genes
-morgan found that white is on x- xsome

In humans..females XX, males XY
males has only 1 copy of genes on x xsome..
-in males the alleles on the x x'some always dictate the phenotype we see

1 copy (males only have 1 copy of genes on x xsome)

Genes on x or y x'some
-xlinked, y linked

Autosomal

-in flies..# of x xsomes..
..in some cases you get XO inds...male
-in humans..absence or presence of y- x'some
XO- female

Skips generations
-mostly seen in males
-affected mom will have 100% affected males children
-unaffeced mom can also still have affected so

X-linked disorder..royal family
-blood doesnt clot

Have to have some to equalize the amt of protein made from genes on x
-fixed by dosage compensation

Male flies produce 2 times amt of proteins on x- xsom