Question

Identify and name the structure, in the figure given below. Also specify its function

Answer 1

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. ... DNA and histone proteins are packaged into structures called chromosomes.

In eukaryotes the chromosomes are multiple large, linear and are present in the nucleus of the cell.

Each chromosome typically has one centromere and one or two arms that project from the centromere.

Structurally, each chromosome is differen­tiated into three parts—

Pellicle

Matrix

Chromonemata

Pellicle

It is the outer envelope around the substance of chromosome.

It is very thin and is formed of achromatic substances.

Matrix

It is the ground substance of chromosome which contains the chromonemata.

It is also formed of non-genic materials.

Chromonemata

Embedded in the matrix of each chromosome are two identical, spirally coiled threads, the chromonemata.

The two chromonemata are also tightly coiled together that they appear as single thread of about 800A thickness.

Each chromonemata consists of about 8 mi­crofibrils, each of which is formed of a double helix of DNA.

In mitotic metaphase chromosomes, the following structural feature (except chromomere) can be seen under the light mi­croscope:

(1) Chromatid,

(2) Chromonema,

(3) Chromomeres,

(4) Centromere,

(5) Secondary constriction or Nucleolar organizer,

(6) Telomere and

(7) Satellite.