name 2 amino acids present in the basic protien of chromosome
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Two types of proteins, i.e., acidic and basic proteins are found associated with DNA in chromosome.
Protamines:
These are simple proteins of molecular weight less than 4000 Daltons. Rich in basic amino acid arginine, found in spermatozoa of some fish (salmon), snail, fowl, etc. They are helically rapped around DNA. Polypeptides of protamine consists of 28 amino acid residue (19 arginines, 8-9 non-basic amino acids).
Histones:
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Small basic proteins associated with DNA of eukaryotic cells. They are structural proteins of chromatin and act as gene repressors also. In a wide variety of plants and animals, the ratio of DNA: Histone =1:1. There are 5 types of Histones i.e., HI (H5), H2A, H2B, H3 and H4. Histones are rich in arginine and lysine (basic amino acids). They lack tryptophan. Histones are highly modified as well as conserved proteins; with very little difference in amino acid sequences. On the basis of arginine and lysine contents, they are divided into 3 groups.
(i) High lysine rich — HI
(ii) Lysine rich — H2A, H2B
(iii) Arginine rich – H3, H4
Histones tend to depress genetic activity. They make DNA. They are structurally important in packaging DNA molecules.
Protamines:
These are simple proteins of molecular weight less than 4000 Daltons. Rich in basic amino acid arginine, found in spermatozoa of some fish (salmon), snail, fowl, etc. They are helically rapped around DNA. Polypeptides of protamine consists of 28 amino acid residue (19 arginines, 8-9 non-basic amino acids).
Histones:
ADVERTISEMENTS:
Small basic proteins associated with DNA of eukaryotic cells. They are structural proteins of chromatin and act as gene repressors also. In a wide variety of plants and animals, the ratio of DNA: Histone =1:1. There are 5 types of Histones i.e., HI (H5), H2A, H2B, H3 and H4. Histones are rich in arginine and lysine (basic amino acids). They lack tryptophan. Histones are highly modified as well as conserved proteins; with very little difference in amino acid sequences. On the basis of arginine and lysine contents, they are divided into 3 groups.
(i) High lysine rich — HI
(ii) Lysine rich — H2A, H2B
(iii) Arginine rich – H3, H4
Histones tend to depress genetic activity. They make DNA. They are structurally important in packaging DNA molecules.
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