DNA: Difference between revisions
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< | <StructureSection load='B-DNA.pdb' size='540' frame='true' align='left' caption='B-DNA' scene='DNA/B-dna/7'> | ||
'''Deoxyribonucleic acid''' or '''DNA''' is a molecule which is the carrier of genetic information in nearly all the living organisms. It contains the biological instructions for the development, survival and reproduction of organisms. | '''Deoxyribonucleic acid''' or '''DNA''' is a molecule which is the carrier of genetic information in nearly all the living organisms. It contains the biological instructions for the development, survival and reproduction of organisms. | ||
DNA is found in the nucleus of a cell where it is packaged into a compact form called a chromosome with the help of several proteins known as histones. It is also found in cell structures called mitochondria. However in case of prokaryotes DNA is not enclosed in a nucleus or a membrane but is present in the cytoplasm. The DNA in prokaryotes in generally circular and supercoiled without any histones. DNA stores genetic information as a sequence of nucleotides in special regions known as genes which are used to make proteins. The expression of genetic information into proteins is a two-stage process wherein the sequence of nucleotides in DNA is converted to a molecule called Ribonucleic acid or [[RNA]] by a process called [[transcription]]. RNA is used to make proteins by another process called [[translation]]. The human genome contains nearly 3 · 10<sup>9</sup> bases with around 20,000 genes on 23 chromosomes. <ref name='gene'>http://www.genome.gov/25520880 </ref> | DNA is found in the nucleus of a cell where it is packaged into a compact form called a chromosome with the help of several proteins known as histones. It is also found in cell structures called mitochondria. However in case of prokaryotes DNA is not enclosed in a nucleus or a membrane but is present in the cytoplasm. The DNA in prokaryotes in generally circular and supercoiled without any histones. DNA stores genetic information as a sequence of nucleotides in special regions known as genes which are used to make proteins. The expression of genetic information into proteins is a two-stage process wherein the sequence of nucleotides in DNA is converted to a molecule called Ribonucleic acid or [[RNA]] by a process called [[transcription]]. RNA is used to make proteins by another process called [[translation]]. The human genome contains nearly 3 · 10<sup>9</sup> bases with around 20,000 genes on 23 chromosomes. <ref name='gene'>http://www.genome.gov/25520880 </ref> | ||
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<scene name='DNA/B-dna/7'>Restore View</scene> | <scene name='DNA/B-dna/7'>Restore View</scene> | ||
== Features of a DNA Molecule == | == Features of a DNA Molecule == | ||
=== Double Helix === | === Double Helix === | ||
<scene name='User:Adithya_Sagar/Sandbox_DNA/B-dna/4'>DNA</scene> consists of two polynucleotide chains, <scene name='DNA/B-dna/16'>twisted around each other to form a double helix</scene>. The <scene name='DNA/B-dna/29'>nucleotide</scene> in DNA is composed of of a <scene name='DNA/B-dna/30'>5' phosphorylated sugar</scene> which is a beta-D-2'- deoxyribose and a purine or a pyrimidine <scene name='User:Adithya_Sagar/Workbench_newDNA/B-dna/18'>base</scene>. The four types of bases are the two double ringed purine base <scene name='DNA/B-dna/22'>Adenine (A)</scene> and <scene name='DNA/B-dna/23'>Guanine (G)</scene> and the two single pyrimidine bases <scene name='DNA/B-dna/28'>Thymine (T)</scene> and <scene name='DNA/B-dna/27'>Cytosine (C)</scene>.Each nucleotide in a DNA chain is linked to another via <scene name='User:Adithya_Sagar/Workbench/Retest/B-dna/2'>3',5' phosphodiester bond</scene>. There are four nucleotides in DNA. The sugar-phosphate backbone of the DNA is very regular owing to the phosphodiester linkage whereas the ordering of bases is highly irregular.<ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | |||
DNA consists of two polynucleotide chains, <scene name='DNA/B-dna/16'>twisted around each other to form a double helix</scene>. The <scene name='DNA/B-dna/29'>nucleotide</scene> in DNA is composed of of a <scene name='DNA/B-dna/30'>5' phosphorylated sugar</scene> which is a beta-D-2'- deoxyribose and a purine or a pyrimidine <scene name='User:Adithya_Sagar/Workbench_newDNA/B-dna/18'>base</scene>. The four types of bases are the two double ringed purine base <scene name='DNA/B-dna/22'>Adenine (A)</scene> and <scene name='DNA/B-dna/23'>Guanine (G)</scene> and the two single pyrimidine bases <scene name='DNA/B-dna/28'>Thymine (T)</scene> and <scene name='DNA/B-dna/27'>Cytosine (C)</scene>.Each nucleotide in a DNA chain is linked to another via <scene name='User:Adithya_Sagar/Workbench/Retest/B-dna/2'>3',5' phosphodiester bond</scene>. There are four nucleotides in DNA. The sugar-phosphate backbone of the DNA is very regular owing to the phosphodiester linkage whereas the ordering of bases is highly irregular.<ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | |||
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