The structure of nucleic aids
The structure of DNA
DNA is composed of two polynucleotide strands wound around each other in a double helix
The pentose sugar in the nucleotides is deoxyribose
There are four organic bases in DNA: two purines, adenine and guanine and two pyrimidines, cytosine and thymine
The bases of the two strands face each other, pointing inwards. Adenine always lines up opposite thymine and guanine always lines up opposite cytosine. Hydrogen bonds join the bases and maintain the shape of the double helix
A DNA molecule is very long and thin and is tightly coiled within the chromosome
The nucleotides in one strand. are arranged in the opposite direction from those in the complementary strand. the strands are "antiparallel"
DNA functions
It is a very stable molecule
It is a very large molecule and carries a large amount of genetic information
The two strands are able to separate
The structure of RNA
RNA is a single stranded polynucleotide
RNA contains the pentose sugar ribose
RNA contains the purine bases, adenine and guanine and the pyrimidine bases cytoplasm and uracil
Three types of RNA involved in the process of protein synthesis
1)Messenger RNA, is a long, single-stranded molecule. it is synthesised in the nucleus and carries the genetic code from the DNA to the ribosomes in the cytoplasm
2)Ribosomal RNA, is found in the cytoplasm and comprises large, complex molecules. They are the site of translation of the genetic code into protein
3)Transfer RNA, is a small single-stranded molecule, which folds so that in places , there are base sequences forming complementary pairs. Carries a sequence of three bases called the anticodon