DNA Structure and replication

 DNA (deoxyribonucleic Acid) carries the genetic code. DNA Structure

 DNA (deoxyribonucleic Acid) carries the genetic code.  Found in the chromosomes – it has a double helix shape (like a twisted ladder) DNA Structure

 DNA (deoxyribonucleic Acid) carries the genetic code.  Found in the chromosomes – it has a double helix shape (like a twisted ladder)  The side strands are made of alternating sugar and phosphate groups. DNA Structure

 DNA (deoxyribonucleic Acid) carries the genetic code.  Found in the chromosomes – it has a double helix shape (like a twisted ladder)  The side strands are made of alternating sugar and phosphate groups.  The ‘rungs’ are made of paired nitrogenous bases. DNA Structure

 DNA (deoxyribonucleic Acid) carries the genetic code.  Found in the chromosomes – it has a double helix shape (like a twisted ladder)  The side strands are made of alternating sugar and phosphate groups.  The ‘rungs’ are made of paired nitrogenous bases.  Each strand of DNA is made of many repeating units called nucleotides (a sugar, a phosphate, and a nitrogen base) DNA Structure

Nitrogen base (any one of A, T, C, G) Deoxyribose Sugar Phos phate

 A always pairs with T (adenine and thymine)  C always pairs with G (cytosine and guanine) DNA Structure

 A always pairs with T (adenine and thymine)  C always pairs with G (cytosine and guanine)  The pairs are held together by weak hydrogen bonds – therefore holding the 2 strands of DNA together. DNA Structure

 A always pairs with T (adenine and thymine)  C always pairs with G (cytosine and guanine)  The pairs are held together by weak hydrogen bonds – therefore holding the 2 strands of DNA together.  The genetic code is the sequence of bases along one strand – 3 bases = a triplet. DNA Structure

 A always pairs with T (adenine and thymine)  C always pairs with G (cytosine and guanine)  The pairs are held together by weak hydrogen bonds – therefore holding the 2 strands of DNA together.  The genetic code is the sequence of bases along one strand – 3 bases = a triplet.  A triplet codes for a particular amino acid, and amino acids together make proteins. DNA Structure

 All the triplets that code for one complete protein make up a gene. DNA Structure

 All the triplets that code for one complete protein make up a gene.  Different sequences of bases along a gene can produce proteins that are slightly different (eg. One sequence would code for brown eyes, and one would code for blue) DNA Structure

 All the triplets that code for one complete protein make up a gene.  Different sequences of bases along a gene can produce proteins that are slightly different (eg. One sequence would code for brown eyes, and one would code for blue)  Different forms of a gene are called alleles. DNA Structure