Embryology Problem Based Question (Q4 - Langman)

ANATOMY AIIMS, GROSS ANATOMY, EMBRYOLOGY, NEUROANATOMY, MICROANATOMY, APPLIED/ CLINICAL ANATOMY

In addition to numerical abnormalities, what types of chromosomal alterations occur?

Answer:

In addition to numerical abnormalities, there are several types of chromosomal alterations that can occur, including structural abnormalities and genomic imprinting disorders.

Structural abnormalities involve changes in the structure of chromosomes, such as deletions, duplications, inversions, and translocations. Deletions occur when a part of a chromosome is missing, while duplications occur when a segment is copied. Inversions involve a segment of the chromosome that is reversed in orientation, and translocations occur when segments of non-homologous chromosomes are exchanged.

Genomic imprinting disorders are caused by changes in the epigenetic marking of genes, which can result in the silencing of certain genes. These disorders can result in various clinical conditions, such as Angelman syndrome and Prader-Willi syndrome.

Deletions involve the loss of a segment of a chromosome, resulting in the absence of the genetic material contained in that segment. This can lead to various genetic disorders, depending on which genes are missing. For example, cri-du-chat syndrome is caused by a deletion of part of chromosome 5 and is characterized by a distinctive cry, intellectual disability, and other physical and developmental abnormalities.

Duplications occur when a segment of a chromosome is duplicated, resulting in the presence of extra genetic material. Depending on the size and location of the duplication, this can lead to various developmental and intellectual disabilities.

Inversions occur when a segment of a chromosome is flipped around 180 degrees, changing the orientation of the genetic material within that segment. Inversions can have varying effects depending on the location and size of the inverted segment, but may cause no significant clinical effects in some cases.

Translocations occur when a segment of one chromosome breaks off and becomes attached to another chromosome. This can lead to a rearrangement of genetic material and can cause various clinical syndromes, depending on the specific chromosomes involved. For example, the Philadelphia chromosome, which is a translocation between chromosomes 9 and 22, is associated with chronic myeloid leukemia.

In addition to these structural abnormalities, there are also chromosomal disorders that are caused by changes in the epigenetic marking of genes. Genomic imprinting disorders occur when certain genes are silenced due to abnormal epigenetic modifications, resulting in clinical syndromes such as Angelman syndrome and Prader-Willi syndrome.

References:

Sadler, T. W. (2019). Langman's medical embryology (14th ed.). Wolters Kluwer.

Lewis, R. (2020). Human genetics: concepts and applications (12th ed.). McGraw-Hill Education.