CMMB 413 Lecture Notes - Lecture 5: Sister Chromatids, Tetrasomy, Monosomy

• School: University of Calgary
• Department: Cellular, Molecular and Microbial Biology
• Course: CMMB 413
• Professor: Christopher Wang

Document Summary

The principles of clinical cytogenetics part 4. Loss of a chromosome segment > chromosome imbalance. Autosomal deletions occur at 1 in 7000 live birth. Formation of a terminal (at the end of chromosome) or interstitial (along a chromosome arm) deletion by chromosome breakage. Deletion can be caused by unequal crossing over between misaligned homologous chromosomes or sister chromatids. Haploinsufficiency is the inability of a single copy of a gene to carry out the function normally performed by two copies. Monosomy: loss of chromosomal segment, leading to chromosome imbalance. If we see autosomal deletions that are happening in live births, we see a lot of unbalanced cases. Interstitial: some middle fragment of arm is deleted. Another mechanism for unbalanced: unequal crossing over. Have repetitive regions on one chromosome, when two chromosomes undergo crossing over and they are not aligned properly, see that after the crossing over product, the misalignment could cause a deletion on one chromosome.