Wednesday, 10 August 2005
A chromatin is the material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.
Wednesday, 10 August 2005
Guanine a compound that occurs in guano and fish scales, and is one of the four constituent bases of nucleic acids.
A purine derivative, it is paired with cytosine in double-stranded DNA.
Alternative name: 6-oxy-2-aminopurine.
Chemical formula: C 5 H 5 N 5 O.
Wednesday, 10 August 2005
Adenine is a compound that is one of the four constituent bases of nucleic acids.
Adenine is a purine derivative, it is paired with thymine in double-stranded DNA.
Alternative name: 6-aminopurine.
Chemical formula: C 5 H 5 N 5.
Wednesday, 10 August 2005
Cytosine is a compound found in living tissue as a constituent base of nucleic acids. It is paired with guanine in double-stranded DNA.
Cytosine is a pyrimidine derivative.
Its chemical formula: C 4 H 5 N 3 O.
Saturday, 1 April 2006
Thymine is a compound that is one of the four constituent bases of nucleic acids.
Thymine is a pyrimidine derivative, it is paired with adenine in double-stranded DNA.
Alternative name: 5-methyluracil.
Chemical formula: C 5 H 6 N 2 O 2
Sunday, 14 June 2009
Heteroaromatic denotes an organic compound with a ring structure that is both heterocyclic and aromatic.
Wednesday, 10 August 2005
Pyrimidine is a colorless crystalline compound with basic properties (see bullet point below).
It is a heteroaromatic compound with a chemical formula:
C 4 H 4 N 2.
- Pyrimidine base is a substituted derivative of this, esp. the bases thymine and cytosine present in DNA.
Wednesday, 10 August 2005
A purine compound is colorless and crystalline with basic properties, and forms uric acid on oxidation.
It is a bicyclic compound with a chemical formula of C 5 H 4 N 4.
A purine base is a substituted derivative of this, especially the bases adenine and guanine present in DNA and RNA.
Wednesday, 10 August 2005
Cytidine is a nucleoside composed of cytosine linked to ribose, obtained from RNA by hydrolysis.
Wednesday, 10 August 2005
Adenosine is a compound consisting of adenine combined with ribose, one of four nucleoside units in RNA.
Wednesday, 10 August 2005
A neucleoside is a compound (e.g., adenosine or cytidine) commonly found in DNA or RNA, consisting of a purine or pyrimidine base linked to a sugar.
Wednesday, 10 August 2005
A histone is any of a group of basic proteins found in chromatin.
Wednesday, 10 August 2005
A chromatid is one of the two threadlike strands into which a chromosome divides longitudinally during cell division.
Each contains a double helix of DNA.
ORIGIN
Early 20th century.
From the Greek khroma, khromat meaning ‘color’ + -id.
Wednesday, 7 November 2007
A nucleotide is a compound consisting of a nucleoside linked to a phosphate group.
Nucleotides form the basic structural unit of nucleic acids such as DNA.
Refer Gernetic Nuclea.
Wednesday, 10 August 2005
RNA, short for ribonucleic acid, a nucleic acid present in all living cells.
Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information.
Wednesday, 10 August 2005
Nucleic acids are complex organic substances present in living cells, esp. DNA or RNA, whose molecules consist of many nucleotides linked in a long chain.
Thursday, 21 May 2009
A chromosome is a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
- Each chromosome consists of a DNA double helix bearing a linear sequence of genes, coiled and recoiled around aggregated proteins (histones).
- Their number varies from species to species: humans have 22 pairs plus the two sex chromosomes (two X chromosomes in females, one X and one Y in males).
- During skin cell division, each DNA strand is duplicated, and the chromosomes condense to become visible as distinct pairs of chromatids joined at the centromere.
Bacteria and viruses lack a nucleus and have a single chromosome without histones.
Thursday, 18 December 2008
DNA, short for deoxyribonucleic acid, is a self-replicating material present in nearly all living organisms as the main constituent of chromosomes.
DNA is the carrier of genetic information.
Each molecule of DNA consists of two strands coiled around each other to form a double helix, a structure like a spiral ladder. Each rung of the ladder consists of a pair of chemical groups called bases (of which there are four types), which combine in specific pairs so that the sequence on one strand of the double helix is complementary to that on the other.
It is the specific sequence of bases that constitutes the genetic information.
ORIGIN
1930s.
Deoxyribonucleic from a blend of deoxyribose and nucleic acid.
Wednesday, 10 August 2005
The centromere is the point on a chromosome by which it is attached to a spindle fiber during cell division.
ORIGIN
1920s, from the Latin centrum (meaning center ) + Greek meros meaning ‘part.’
Thursday, 8 October 2009
In biochemistry, a helix is an extended spiral chain of atoms in a protein, nucleic acid, or other polymeric molecule.
ORIGIN
Middleid 16th century.
In the architectural sense [spiral ornament], via Latin, "Helix" from Greek.
Wednesday, 10 August 2005