BIOL 222 Lecture Notes - Lecture 20: Ion, Meiosis, Haploinsufficiency
Document Summary
Biol 222 - lecture 20 - chromosome variation. Changes in chromosome structure: deletions, duplications, inversions and translocations affecting several genes. Repetitive dna - stretches of dna that repeat themselves throughout a genome, either in tandem or interspersed along the genome. Unbalanced rearrangements: change in gene dosage, net gain or loss of dna. Duplication and/or deletion: can have minor to severe consequences depending on the genes that are affected, deletions are generally more detrimental than duplications. A chromosome region that has been doubled. Heterozygous duplication phenotypes are less severe than homozygous duplications. Gene dosage imbalance - affects gene regulation and/or protein activity: duplications will result in excess product of the duplicated gene/genes. Still many issues if heterozygous: gene dosage, pseudodominance, haploinsufficiency. Pseudodominance - a chromosomal deletion will uncover recessive alleles such that the recessive phenotype is expressed. Haploinsufficiency - not enough gene product is made to express the wild-type phenotype even if the remaining allele is wild-type.
