DNA and RNA

DNA and Chromosomes Prokaryotes do not have a nucleus and their DNA is located in the cytoplasm They usually have a single circular DNA molecule (a chromosome)

DNA and Chromosomes Eukaryotes are more complex, so they have a nucleus and this is where the DNA is housed Found as a number of chromosomes which vary between species

OBJ: describe the experiments of Watson and Crick and R OBJ: describe the experiments of Watson and Crick and R. Franklin, which led to the discovery of the structure of the DNA double helix. History of DNA

DNA Replication Watson and Crick discovered the double helix structure of DNA this structure explains how the molecule may be replicated Each strand of the double helix has all of the information required to construct the other strand = complimentary

OBJ describe the structure of a nucleotide and list the 4 DNA nucleotides OBJ describe how nucleic acids are made of long chains of nucleotides

Structure of DNA Long molecule made up of monomer subunits called nucleotides Each nucleotide is made of three parts: 5-Carbon Sugar Phosphate group A Nitrogenous base

Sugar-Phosphate Backbone The outer structure of the DNA molecule Composed of a 5-Carbon sugar (in DNA it is deoxyribose), and a Phosphate group The sugar molecules bonds to the nitrogenous bases The Phosphate groups hold the sugars together

Nitrogenous Bases These are the molecules that bond the two complimentary strands of DNA together Held together between the two strands by Hydrogen bonds, these are very weak bonds (for breaking) Can be: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Adenine will always bond with Thymine Guanine will always bond with Cytosine

Nitrogenous Base Pairs

OBJ: explain the functions of the main enzymes involved in DNA replication

DNA Replication Separating the two strands allows for new strand to be made following the rules of base pairing Replication begins at various points on the chromosome and continues until the entire chromosome has been copied

Duplicating the DNA Strand This process occurs before the cell divides, and is called replication (this would be Interphase) During replication, the DNA separates into two strands, then two new complimentary strands are produced using the rules of base pairing. Each strand of the original serves as a template for the new strand This process allows each daughter cell to have an exact copy of the parent cell’s DNA

How does that happen? This process is carried out by a collection of enzymes They “unzip” the DNA molecule (break the Hydrogen bonds between the bases) DNA Polymerase is the enzyme responsible for assembling the new DNA strands, it also proofreads the new strand to look for errors