DNA structure GCSE - good explanation of the details and transcripts PDF

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DNA nucleotide structure

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Nucleotides are formed from a pentose sugar, phosphate, and a base. Phosphate links neighbouring sugars together (PO43-) The sugar is either ribose for RNA or deoxyribose for DNA, which has one less oxygen Four types of bases, which comprise the coded genetic message Nitrogen-based ring structures Cytosine (C), Guanine (G), Adenine (A), Thymine (T) Nucleotides form sequences, which are instructions for the organism Changes to nucleotides cause mutations

State the names of the four bases in DNA  

Purines – Two Ringed Bases Adenine (A) Guanine (G)

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Pyrimidines – Single Ringed Bases Cytosine (C) Thymine (T) Uracil replaces Thymine in RNA (U)

DNA nucleotides are linked together by covalent bonds into a single strand      

DNA composed of two polynucleotide chains Nucleotides are covalently bonded Bond is a phosphodiester Two covalent bonds between the OH- and acidic phosphate group Nucleotides bond at the 3l (three prime) end of the molecule To form the polynucleotide, the nucleotides condense together one at a time, giving water in the reaction

DNA double helix is formed using complementary base pairing and hydrogen bonds   

Complementary means matching A double helix is made up of two anti parallel polynucleotide chains Bases pair and are bonded with hydrogen bonds Adenine and thymine are the same distance apart as guanine and cytosine

Molecular structure of DNA      

DNA is made up of two anti-parallel polynucleotide chains They form the double helix (“spiral” structure) The DNA has a sugar-phosphate backbone Bonded with complementary base pairs Adenine to Thymine Cytosine to Guanine...