ICSE Class 10 Answered

please tell me about the structure of dna and chromosome. Please tell me about the different proteins

Asked by kshhitij | 27 Feb, 2013, 01:32: PM

Expert Answer

DNA i.e. Deoxyribonucleic acid is a long linear double helical polymer found in the nucleus of a cell and formed from nucleotides. It is associated with the transmission of genetic information.

The backbone of DNA is based on a repeated pattern of a sugar group and a phosphate group. The sugar present is deoxyribose. A phosphate group is attached to the sugar molecule in place of the -OH group on the 5' carbon. In DNA there are 4 bases, which are cytosine (C), thymine (T), adenine (A) and guanine (G). A DNA strand is simply a string of nucleotides joined together. The phosphate group on one nucleotide links to the 3' carbon atom on the sugar of another one

Chromosomes are thr?e?a?d?l?i?k?e? linear strand of DNA and associated proteins that carries th??e genes and functions in the transmission of hereditary information??.? ??T?h?e?y? ?a?r?e? ?l?o?c?a?t?e?d? ????in the nucleus of eukaryotic cells.

Chromosomes are made from DNA. DNA carry the genetic code that determines the characteristics of a living thing. A gene is a short section of DNA. Each gene codes for a specific protein by specifying the order in which amino acids must be joined together. The cells nucleus contains chromosomes made from long DNA molecules.

Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved. The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. Other non-specific DNA-binding proteins in chromatin include the high-mobility group proteins, which bind to bent or distorted DNA. These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that make up chromosomes. A distinct group of DNA-binding proteins are the DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication protein A is the best-understood member of this family. These binding proteins seem to stabilize single-stranded DNA.

Answered by | 27 Feb, 2013, 10:05: PM