Chromosomal Aberrations Flashcards
What are chromosomal aberrations?
Alterations in the structure or number of chromosomes.
What are the two main types of alterations in chromosomal aberrations?
Alterations in the number of genes and alterations in the location of genes.
Define deletions in the context of chromosomal aberrations.
Loss of a chromosomal segment; could be homozygous or heterozygous.
What genetic effects can deletions cause?
Lethal in the homozygous and hemizygous condition, reduced viability, modified phenotypic ratio.
Fill in the blank: The phenotypic ratio in a normal cross is _______.
1AA : 2Aa : 1aa
What is pseudodominance?
Expression of a recessive phenotype due to deletion of a dominant allele.
Provide an example of a condition caused by deletion.
Cri du chat syndrome due to a deletion in the short arm of chromosome #5.
Define duplications in chromosomal aberrations.
Repeated portion in a chromosome due to unequal crossing over or errors in replication.
What is gene redundancy?
Presence of multiple copies of a gene, allowing for greater gene product production.
Provide an example of gene redundancy in organisms.
- 400 copies of rDNA in Xenopus laevis oocytes
- Bar eye in Drosophila melanogaster
- Waxy gene in corn
What occurs during inversions in chromosomes?
Parts of chromosomes become detached, turn through 180 degrees, and reinserted in reversed order.
What are the two types of inversions?
- Paracentric Inversion
- Pericentric Inversion
What is a paracentric inversion?
Inversion situated in a chromosome arm to one side of the centromere.
What condition can arise from a maternal paracentric inversion of chromosome 15?
A child with bisatellited, dicentric chromosome 15.
What does a pericentric inversion include?
The centromere.
What is reciprocal translocation?
Interchange of blocks of genes between two nonhomologous chromosomes.
What is the result of reciprocal translocation on linkage relationships?
Linkage relationships between genes change.
True or False: Translocation heterozygotes exhibit a cross-like configuration during meiotic prophase.
True
What is the genetic consequence of inversions in heterozygotes?
A loop forms from the pairing of the inverted and non-inverted regions.
What is the significance of the KIT receptor tyrosine kinase in mammals?
Essential for melanocyte precursor migration, localization, and survival.
What pigmentation disorder is associated with mutations in the KIT gene?
Piebaldism.
