BISC 202 Lecture Notes - Lecture 21: Down Syndrome, Centromere, Myc

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 202
• Professor: Carol Wenzel

Document Summary

Translocations alter the location of chromosomal segments in the genome: a (cid:373)o(cid:448)e(cid:373)e(cid:374)t of a (cid:272)hro(cid:373)oso(cid:373)al seg(cid:373)e(cid:374)t to a (cid:374)e(cid:449) lo(cid:272)atio(cid:374) i(cid:374) the ge(cid:374)o(cid:373)e, a re(cid:272)ipro(cid:272)al tra(cid:374)slo(cid:272)atio(cid:374): Involves the exchange of segments between two nonhomologous chromosomes. Has an unusual synapsis configuration during meiosis. Pairing of translocations: just like i(cid:374)(cid:448)ersio(cid:374)s, (cid:272)hro(cid:373)oso(cid:373)es (cid:449)ith tra(cid:374)slo(cid:272)atio(cid:374)s (cid:449)ill still pair (cid:449)ith the ho(cid:373)ologous parts, re(cid:272)ipro(cid:272)al tra(cid:374)slo(cid:272)atio(cid:374)s (cid:272)a(cid:374) (cid:271)e dra(cid:449)(cid:374) to li(cid:374)e up as a(cid:374) x-shape, t(cid:449)o possi(cid:271)le (cid:272)hromosome segregation patterns: One that leads to a normal and a balanced gamete (called alternate segregation) One that leads to gametes containing duplications and deficiencies (called adjacent segregation: re(cid:272)ipro(cid:272)al tra(cid:374)slo(cid:272)atio(cid:374)s (cid:272)a(cid:374) (cid:271)e dra(cid:449)(cid:374) to line up as an x-shape. Robertsonian translocation: i(cid:374)(cid:448)ol(cid:448)es (cid:271)reaks at the e(cid:454)tre(cid:373)e e(cid:374)ds of the short ar(cid:373)s of t(cid:449)o (cid:374)o(cid:374)ho(cid:373)ologous a(cid:272)ro(cid:272)e(cid:374)tri(cid:272) chromosomes, fa(cid:373)ilial do(cid:449)(cid:374) s(cid:455)(cid:374)dro(cid:373)e is a(cid:374) e(cid:454)a(cid:373)ple of this, leads to o(cid:374)e less (cid:272)hro(cid:373)oso(cid:373)e.