CH 15; Sex Chromosomes and Linked Genes

chromosomal theory of inheritance

• genes have specific loci

• chromosomes undergo segregation & independent assortment

x linkage

the x-linked recessive alleles are expressed in males because males have only one x chromosome

barr body

an inactive x chromosome

Frequency and Genetic Mapping

the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency

Aneuploidy

abnormal # of a particular chromosome

• monosomic & trisomic zygotes

polyploid

more than2 sets of chromosomes

• triploidy & tetraploidy

klinefelter syndrome

XXY

Trisomy X

XXX

Turner Syndrome

X0

deletion

removes a chromosomal segment

duplication

repeats a segment

inversion

reverses a segment within a chromosome

translocation

moves a segment from one chromosome to a nonhomologous chromosome. In a reciprocal translocation, the most common type, nonhomologous chromosomes exchange fragments.

cri du chat (cry of the cat)

deletion in chromosomes 5

chronic myelogenous leukemia (CML)

translocation of chromosomes