HOUSEKEEPING ITEMS HOUSEKEEPING ITEMS Goals and objectives of the course Goals and objectives of the course 1 Start from small molecules small molecules 4 Cells make up individuals and individuals need to reproduce Therefore chromosomes mitosis meiosis and genetics lectures individuals 2 Continue to coverage of macromolecules found in all living organisms macromolecules 5 Individuals need to express their genes DNA RNA and Proteins individuals species 6 What type of individuals are there species diversity populations 3 Place macromolecules in a cell find relation to cellular organelles cells 11 1 DNA and RNA Structure and Function The work of Mendel and others provided information about the nature of deoxyribonucleic acid DNA Genes occur on chromosomes Mutations in genes caused metabolic errors DNA is composed of nucleotides 7 Individuals in populations have ecological and evolutionary aspects populations communities ecosystems Structure of DNA The research of several scientists helped determine the structure of DNA Erwin Chargaff Rosalind Franklin James Watson and Frances Crick Chargaff s Rules Chargaff s Rules DNA contains four types of nucleotides differing in the nitrogencontaining base each contains The purine base adenine A The pyrimidine base cytosine C The purine base guanine G The pyrimidine base thymine T A nucleotide from DNA contains one base one phosphate group and the sugar deoxyribose 1 Chargaff s Rules Chargaff s Rules cont Chargaff s Rules cont Chargaff s Rules cont In all organisms the nucleotide bases are found in specific proportions Equal proportions between two bases indicated that the bases were paired in the structure of DNA Chargaff s rules are based on two observations The amount of A C G and T varies from species to species In each species the amount of A is equal to T and the amount of G is equal to C The order in which these nucleotides occur differs producing great variability in the DNA Franklin s X Ray Diffraction Studies Rosalind Franklin used X ray crystallography to study the structure of DNA Franklin took an X ray of fibers present in a concentrated solution of DNA The X ray diffraction pattern suggested that DNA had a helical shape With four nucleotides there are 4140 000 000 possible nucleotide sequences The Watson and Crick Model Watson and Crick developed the definitive model of DNA structure The sugar and phosphate groups are bonded in alternating sequences to form the sides of a twisted ladder Bases are joined by hydrogen bonds to form the rungs of the ladder Complementary base pairing occurs meaning A only bonds with T and G with C 2 The Replication of DNA DNA replication is the process of copying a DNA molecule During replication the original strands serve as templates for the new DNA DNA replication is considered semiconservative because one of the original strands is present in each new DNA helix The Replication of DNA cont DNA replication requires several steps The enzyme helicase unwinds the old strands of the DNA helix New nucleotides are positioned by complementary base pairing and the enzyme DNA polymerase DNA ligase repairs breaks in the backbone The Replication of DNA cont The Replication of DNA cont In eukaryotic cells DNA replication is initiated at multiple points along the DNA strand or origins of replication The replication bubbles spread bidirectionally until they meet The Replication of DNA cont RNA Structure and Function Ribonucleic acid RNA also consists of nucleotides but these nucleotides contain the sugar ribose RNA has adenine cytosine guanine and a fourth base called uracil 3 RNA Structure and Function cont RNA Structure and Function cont Although both RNA and DNA are nucleic acids there are key differences in the structure and function of RNA and DNA Messenger RNA Transfer RNA There are three types of RNA and each is involved in protein synthesis Transfer RNA tRNA is a carrier molecule for amino acids delivering them to the site of protein synthesis Messenger RNA mRNA is produced in the nucleus by a process called transcription As there are 20 different amino acids there are also 20 different types of tRNA Messenger RNA carries genetic information from DNA to the cytosol Ribosomal RNA The two ribosomal RNA rRNA subunits join with proteins in the cytosol to form the subunits of ribosomes The free ribosomes polyribosomes and ribosomes attached to the ER all synthesize proteins 11 2 Gene Expression DNA and RNA are involved in the synthesis of proteins The genes in DNA contain the instructions for the amino acid sequence of a protein 4 11 2 Gene Expression cont Since enzymes are proteins an error in the gene for that enzyme could render the enzyme non functional If an enzyme is defective then the biochemical pathway in which the enzyme participates may also be affected This can create inborn errors in metabolism that lead to metabolic diseases Structure and Function of Proteins Proteins differ in the number and sequence of amino acids This sequence of amino acids gives each protein a unique shape and function The shape of a protein has different levels of organization Primary structure Secondary structure Tertiary structure Structure and Function of Proteins cont From DNA to RNA to Protein In order to synthesize a protein the genetic information in the DNA must be converted to an amino acid sequence Transcription involves the synthesis of mRNA from template DNA During translation the mRNA directs the sequence of amino acids in the protein The Genetic Code The Genetic Code cont Within a gene information for the amino acid sequence of a protein is encoded in a triplet code This triplet code is transcribed into the codons in mRNA These codons provide redundant sequences for the placement of amino acids in a protein 5 Transcription cont Transcription During transcription a strand of mRNA is formed that is complementary to the sequence within the DNA Transcription begins when RNA polymerase binds to the DNA promoter for a gene The DNA helix is unwound and the primary mRNA strand is formed Transcription cont Transcription cont The primary mRNA strand is then processed to remove introns The remaining sequence of genetic information the exons are retained in the mature mRNA for protein synthesis Translation An Overview cont Translation An Overview The translation of a mature mRNA into proteins requires several enzymes tRNA and rRNA The tRNA is a single stranded RNA molecule with an amino acid bound to one end and an