Basics of Undergraduate/university fellows
In some organisms, there are special tissues in which chromosomes undergo structural
specializations.
Such specialized chromosomes are generally termed as SPECIAL TYPES OF
CHROMOSOMES
Luciferase in rDNA technology (biotechnology).pptx
1. Special chromosomes - Introduction
1. SPECIAL CHROMOSOMES 1
SPECIAL TYPES OF CHROMOSOMES
The entire eukaryotic organism consists of normal chromosomal set carrying genetic
material in each cell.
The chromosomal set is specific to particular species level & varies across kingdom.
In eukaryotes, chromosomes are to standard structure and function of chromosomes as
observed in mitotic or meiotic cells in plants and animals.
Some eukaryotes besides possessing the usual type of chromosomes contain some
unusual chromosomes.
These unusual chromosomes are present only in certain special tissues (not seen in other
tissues) and at some particular stage of their life cycle.
In some organisms, there are special tissues in which chromosomes undergo structural
specializations.
Such specialized chromosomes are generally termed as SPECIAL TYPES OF
CHROMOSOMES.
Due to special significance of these chromosomes, a relatively detailed account of these
two types of chromosomes are well accounted.
The special types of eukaryotic chromosomes are classified into following categories:
I. GIANT CHROMOSOMES
These chromosomes are larger in size and are called giant chromosomes.
1. Polytene/Salivary Chromosome
2. Lampbrush Chromosome
II. SUPERNUMERARY CHROMOSOMES
These chromosomes add on to number of normal chromosome and are termed as
Supernumerary Chromosomes.
3. B-Chromosomes
III. Holo-kinetic chromosomes
The chromosomes of most plants and animals have centromeres that are situated at one
specific position in each chromosome.
In a number of animals, an especially in insect of the order Hemiptera and a few, mostly
monocotyledonous plants (Juncales, Cyperales), the kinetic activity is distributed over the
entire chromosome and such chromosomes are called Holokinetic chromosomes.