1 a DNA Genetic information is stored in the order or sequence of nucleotides Nucleotides code for a polypeptide a protein or a RNA molecule tRNA rRNA A genome is all of an organism s genetic material in a cell RNA The intermediary molecule in the flow of genetic information 3 major types of RNA mRNA messenger tRNA transfer rRNA ribosomal Proteins Made of strands of amino acids Types and functions enzymes catalyze reactions structural support transport other molecules hormones coordinate cell activities receptors respond to and bind chemical stimuli defense motor protein storage of amino acids Encodes Genetic Ifo Catalyzes Reactions Building Blocks types Strandedness Structure DNA Yes No Double Double Helix RNA Protein Yes Yes Single Single No Yes Amino Acids Single Single Nucleotides Nucleotide s Repair Systems Yes No No b Replication Copies an organisms DNA The double helix of DNA is unwound and each strand is used as a template for the next This occurs inside the nucleus Transcription The synthesis of mRNA using DNA as a template This also occurs in the nucleus Translation The transcribed mRNA is decoded into a specific protein This happens at the ribosome in the cytoplasm c Ribosomes are composed of RNA They are also the site of protein synthesis where RNA is translated into protein Two subunits of RNA are used to make the proteins tRNA is used to carry amino acids in the cytoplasm to help build the polypeptide chain of proteins Each tRNA attaches to one type of amino acid d The Genetic Code All organisms use the same genetic code A codon triplet of 3 mRNA bases codes for 1 amino acid Multiple codons can code for the same amino acid Your tRNA with the anticodon binds to the mRNA codon e Mutation A change in the genetic material of a cell They can be point mutation a change in one nucleotide substitution of a nucleotide or insertions and deletions of a nucleotide These may or may not alter the codon and the amino acid that it would code for These lead to being silent no amino acid change missense changes the amino acid or nonsense which leads to a stop signal and no protein f A gene is a unit of hereditary information g A chromosome is one long double stranded helical DNA molecule h Chromatin is what makes up chromosome Chromatin is composed of DNA and proteins that bind to DNA Chromosomes contain euchromatin and heterochromatin Euchromatin is loosely packed DNA around nucleosomes It is actively transcribed Heterochromatin is tightly packed and is genetically inactive not transcribed a Gene expression the flow of genetic information occurs through transcription and translation Gene regulation is the control of gene expression i e regulating transcription and translation Some genes have constitutive expression meaning they re always on and some are expressed or repressed as needed in facultative expression Since all cells have the same genes it takes regulation of the genes to turn on the right ones needed for the cell b i Transcription factors are regulation of gene expression on a gene level and is the most prevalent form of gene expression They are regulatory proteins that respond to a signal and bind to specific DNA sequences near a gene in transcription ii Control elements are the DNA sequences upstream of a gene where you can find transcription factors Transcription factors bind to the control elements to regulate genes at the initiation of transcription 2 3 Type Function Example Enzymes Catalyze reactions DNA polymerase Structural Support Keratin Collagen Transport Other molecules Hemoglobin Hormones Coordinate cell org activities Insulin Receptors Respond and bind to stimuli G Proteins Defense Motor Proteins Antibodies Actin Storage Of amino acid reserves Ovalbumin 4 a Cells communicate with other cells to decide many things like whether it should divide or not and so they know what to do to keep the body alive If there is a specific function that needs to be carried out it is more efficient to send it to something specific instead of all cells This is done by cell signaling b Reception A signal molecule is received by a receptor molecule on the cell membrane or inside the cell Transduction A stepwise series of chemical reactions initiated by an activated receptor molecule to elicit a specific cellular response Response The end result of a specific signaling pathway c G Protein linked receptors Signal pathway using a cell membrane receptor The receptor activates the G protein which then activates the enzyme Intracellular Receptor The use of the steroid hormone testosterone explanation in picture Multi step pathway a Phosphorylation cascade the transferring of a phosphate group from one to another to reach the target of the original signal Non protein second messenger Cyclic amp cAMP is activates and it turn activates a target protein 5 a b differentiated are multipotent cells i Genomic equivalence all the different cell types in an organism have identical genomes but they express different genes ii Our somatic cells are the same because all cells share the same DNA It is a matter of which genes are expressed that make cells different i Cell potency describes a cells potential to differentiate ii Multipotent Can differentiate into some but not all cell types Adult stem cells Pluripotent Can differentiate into any cell type is obtained from a slightly older embryo Totipotent Can differentiate into an entire ne individual is obtained from an early embryo iii Stem cells Relatively undifferentiated cells that be ne induced to be iv Embryonic stem cells can be totipotent and pluripotent Adult stem cells v You can replace damaged tissues and organs by growing them from stem c d i Determination A process by which a cell differentiates into a particular cell type by expressing a unique set of genes ii Cells can differentiate later in development via induction of cells one cell signals a neighboring cell to change gene expression iii Cytoplasmic determinants Signal molecules that can help regulate gene expression In early development the maternal CD s can regulate early gene expression in embryonic daughter cells either symmetrically or asymmetrically i Cloning Obtaining an adult asexually from a parent somatic cell ii In reproductive cloning you take a nucleus form a differentiated cell from an adult and transplant it into an enucleated and unfertilized egg then implanted into a surrogate mother iii Reproductive cloning is difficult because of incomplete programming of the
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