Structural Changes in Chromosomes
Book Chapter
Al-Ghanim, Abdul Rauf Shakoori, Saira Aftab, and Khalid . 2017
نوع عمل المنشور:
Chromosomal aberrations • Deletion • Duplication • Inversion • Translocation • Genetic imbalance • Heterochromatin • Interstitial deletion • Ring chromosome • Cri-du-chat syndrome • Angelman syndrome • Beckwith-Wiedemann syndrome • Down syndrome • Prader-
مدينة النشر:
Springer (India)
رابط المنشور على الويب:
اسم الجهة الناشرة:
Tariq Ahmad Bhat • Aijaz Ahmad Wani Editors
عنوان الكتاب:
Chromosome Structure and Aberrations
الصفحات:
245 - 274
مستخلص المنشور:
Chromosomes can be structurally identified by their sizes, positions of centromeres
and nucleolar organizers, and patterns of chromomeres, heterochromatin,
and bands. There are four types of aberrations in the chromosomal structure such
as deletions, duplications, inversions, and translocations which can be detected
cytologically under the microscope. Some changes are however too subtle to be
detected cytologically. Deletions represent missing segments of chromosomes.
The homozygous deletions can be lethal, whereas heterozygous deletions can be
nonlethal or lethal and can express recessive genes uncovered by deletion.
Duplications can cause an imbalance in the genetic material, thereby producing
phenotypic effect in the organism and leading to increased variety of gene functions.
Inversions are caused by 180 degree turn of a segment of a chromosome,
which cause little problem for an organism under homozygous condition, but
inversion heterozygotes often have pairing difficulties during meiosis, leading to
formation of inversion loops. Crossing over within loops usually results in inviable
products. The crossover products will be different for pericentric and paracentric
inversions. Translocations involve relocation of a chromosomal segment
to another position in the genome. In heterozygous state, the translocations produce
duplication-deletion meiotic products, which can lead to unbalanced
zygotes, and new gene linkages. Chromosome rearrangements can cause ill
health in human population – infertility and mental retardation being the dominant
effects.
ملف مرفق:
| المرفق | الحجم |
|---|---|
 chromosomestructureandaberrations.pdf | 11.89 ميغابايت |