HMB265H1 Lecture 18: Summary - Lecture 18

• School: UTSG
• Department: Human Biology
• Course: HMB265H1
• Professor: Maria Papaconstantinou

Document Summary

Endoreplication: formed by multiple rounds of replication without any nuclear division. This forms a thick bundle of replicated chromosomes that is much larger than normal mitotic chromosomes. Chromocentre: attaches homologous and non-homologous chromosomes together. Del (df) homozygotes are usually inviable (haploinsuf ciency) Recessive lethals: many genes we have are essential. If we do not have at least one copy, we will not survive. Even having one copy sometimes is not enough. The deletion loop represents the region that has been deleted on the bottom chromosome. This loop is easily visible in polytene chromosomes. The mutant gene (recessive) appears to be dominant. Deletion mapping: del (df) heterozygotes reveals the location of the mutant gene. Mutations are paired against large, overlapping regions of the polytene chromosome. Complementation: cross speci c deletion mutants with different parts of the chromosome deleted. You are looking for the phenotype of the deletion heterozygote (it will reveal the location of the mutant gene).