Introduction
Overview of Chromosome Aberrations
What It Is: A chromosome aberration means any change from the normal structure of chromosomes.
Types: They can change in number (numerical) or structure (structural).
Visibility: These changes can be seen under a microscope when cells are in the metaphase stage of cell division.
How They're Inherited
From Parents: Aberrations can be passed down from parents in sperm or eggs, affecting the whole organism.
After Conception: Sometimes these changes happen after conception, leading to a mix of normal and abnormal cells (mosaicism).
New Mutations: Some are new mutations not seen in the parents (de novo mutations).
Types of Structural Chromosome Aberrations
Inversion: A piece of the chromosome gets flipped around.
Duplication: Extra copies of a part of the chromosome are made.
Deletion: A piece of the chromosome is lost.
Translocation: Parts of chromosomes swap places.
Insertion: A piece of one chromosome gets added to another.
Causes of Deletions and Duplications
Uneven Crossing Over: When chromosomes swap pieces unevenly during cell division.
Double Strand Breaks: Mistakes made when the cell repairs breaks in DNA.
Homologous vs. Non-Homologous End Joining
Preferred Method: Homologous is better because non-homologous can lead to mutations when the correct partner strand isn't available.
Numerical Chromosome Aberrations
Aneuploidy: Having an abnormal number of chromosomes.
Polyploidy: Having extra sets of chromosomes
Autopolyploidy: Extra chromosome sets are from the same species.
Allopolyploidy: Extra chromosome sets are from different species.
Autotriploidy: Having three copies of each chromosome.
Karyotype Evolution and Translocation
Changes like deletions, duplications, and inversions can affect reproduction and lead to new species.
Translocation Issues: Can cause problems with chromosome sorting during cell division and lead to reproductive isolation.
Comparing Human and Ape Chromosomes
Humans have one less chromosome pair than great apes due to a fusion event.
Despite the difference in number, many chromosomes have similar banding patterns and structures.
Polyploidy in Plants vs. Animals
More common in plants and can be beneficial for asexual reproduction.
Polytene Chromosomes
Found in some insect cells, showing areas of active gene expression (puffs), important for understanding gene activity during development.