Chromosomes
Chromosomes are important part of a cell discovered in 1876 by Waldeyer. In 1908 W.S. Sutton observed that genes are located on chromosomes and genetic phenomenon can be explained in terms of chromosomal behavior during cell division particularly during metaphase and anaphase.
Structure of Chromosome
Chromosome comprises two chromatids attached to centromere. Centromere is the point where spindle fibers get attached with them. The position is very important to distinguish the type of chromosome. You can say that on the basis of its position the type and shape of a chromosome can be defined.
Types of Chromosomes
On the basis of centromere’s position, chromosomes can be divided into four types.
1- Telocentric (Centromere present at one end of chromosome)
2- Acrocentric (Centromere present close to one end, so acrocentric chromosomes have very small arms)
3- Metacentric (Centromere present in centre with equal arms)
4- Submetacentric (Centromere present near the centre but not exactly in the centre therefore have an equal arms)
Karytype
It is the term used to describe the total chromosome complement of cell. Study of karytype helps in determining the total number of chromosome present in human beings and in other species.
Chemical Composition of Chromosomes
Chromosomes are chemically composed of DNA and basic protein. These basic proteins are called Histones. DNA and Histones combine together to form a structure which is called Nucleosome. Nucleosome comprises eight molecules of various types of histones with two turns of DNA molecules. Under electron microscope nucleosome appears as a beaded structure of 10nm diameter.
Chromosomes are important part of a cell discovered in 1876 by Waldeyer. In 1908 W.S. Sutton observed that genes are located on chromosomes and genetic phenomenon can be explained in terms of chromosomal behavior during cell division particularly during metaphase and anaphase.
Structure of Chromosome
Chromosome comprises two chromatids attached to centromere. Centromere is the point where spindle fibers get attached with them. The position is very important to distinguish the type of chromosome. You can say that on the basis of its position the type and shape of a chromosome can be defined.
Types of Chromosomes
On the basis of centromere’s position, chromosomes can be divided into four types.
1- Telocentric (Centromere present at one end of chromosome)
2- Acrocentric (Centromere present close to one end, so acrocentric chromosomes have very small arms)
3- Metacentric (Centromere present in centre with equal arms)
4- Submetacentric (Centromere present near the centre but not exactly in the centre therefore have an equal arms)
Karytype
It is the term used to describe the total chromosome complement of cell. Study of karytype helps in determining the total number of chromosome present in human beings and in other species.
Chemical Composition of Chromosomes
Chromosomes are chemically composed of DNA and basic protein. These basic proteins are called Histones. DNA and Histones combine together to form a structure which is called Nucleosome. Nucleosome comprises eight molecules of various types of histones with two turns of DNA molecules. Under electron microscope nucleosome appears as a beaded structure of 10nm diameter.
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