DNA uses doexyribose as the sugar in its nucleotides, nucleotides can have 4 different bases.The different bases are categorised into Purines and Pyrimidines.
Purines are larger and contain double carbon ring structures. Bases A and G are purines.Pyrimidines are smaller and contain single carbon ring structures. Bases C and T and pyrimidines.it is easy to remeber as purines is the large group but has a shorter name.
The DNA double helix is made up of two polynucleotide strands, the strands are joined together by hydrogen bonds between bases. The two strands run in opposite directions (one facing up and one facing down) they are refered to as antiparallel.
The A and T bases form 2 hydrogen bonds whilst C and T form 3 so A will only bond to T and C will only bond to G. this is called complementary base pairing. this ensures a small and large base always pair so the helix is parallel.
The sequence of bases carry genetic info in a code form. the sequence codes for amino acids to make diffrent proteins.
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