DNA & RNA

Griffith and Transformation Frederick Griffith was trying to figure out how bacteria made people sick Pneumonia Cause of pneumonia was not a chemical poison released by disease causing bacteria The heat killed bacteria had passed their disease-causing ability to the harmless strain

Griffith Experiment

Transformation Transformation- process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria Which molecule was responsible?

Avery and DNA Avery, Macleod, and McCarty wanted to determine what molecule in the heat killed bacteria was most important for transformation. *** Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next. Genes are made of DNA ***Deoxyribonucleic acid

The Hershey-Chase Experiment Alfred Hershey and Martha Chase Collaborated in studying viruses Bacteriophage “Bacteria eater” Composed of DNA or RNA core and a protein coat. Bacteriophage enters a bacterium, the virus attaches to the surface of the cell and injects its genetic info into it

The Hershey-Chase Experiment The viral genes act to produce many new bacteriophages and they gradually destroy the bacterium. When the cell splits open, hundreds of new viruses burst out. Need to determine which part of the virus ( the protein coat or the DNA core) entered the infected cell They would determine whether genes were made of protein or DNA

The Hershey-Chase Experiment Concluded- The genetic material of the bacteriophage was DNA, not protein. NEED radioactive stuff

The components and structure of DNA Three critical things genes were known to do – Carry info from 1 generation to the next – Put that info to work by determining the heritable characteristics of organisms – Had to be easily copied, because all of a cell’s genetic info is replicated every time a cell divides

The components and structure of DNA DNA is a long molecule made up of units called nucleotides Two strands form a double helix

The components and structure of DNA Nucleotides 3 components: – Phosphate grp – Pentose ( 5 carbon sugar) - deoxyribose – Nitrogenous base (contain nitrogen)

Four kinds of nitrogenous bases PURINES Guanine Adenine Two ring structure PYRIMIDINES Cytosine Thymine One ring structure

The components and structure of DNA Backbone of a DNA formed by – Sugar and phosphate Nitrogenous bases stick out sideways from chain

The components and structure of DNA

Replication Prokaryote Lack nuclei and other organelles Single circular DNA DNA molecules found in cytoplasm Eukaryote 1000 x amt of DNA than Prokaryote Found in nucleus form of a # of chromosomes Humans- 46 chromosomes Drosophilia fly-8 Giant Sequoia tree- 22

DNA Replication Needs to be folded “nicely” inside of cell to be able to be unraveled easily. DNA and protein packed together to form- chromatin. Chromatin – DNA that is tightly coiled around proteins called histones. DNA and histones form a beadlike structure- nucleosome. Nucleosome- - tightly coiled and super coiled to form chromosomes

DNA Replication

Two parental strands serve as template strands New nucleotides must obey the AT/GC rule End result 2 new double helixes with same base sequence as original

DNA Replication During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template, or model, for the new strand. lated lated

DNA Replication Origin of replication- – Prokaryote- single origin – Eukaryote- multiple origins Starts at replication forks Replication proceeds outwards in opposite directions Enzymes – “unzip” (helicase) a molecule of DNA – Breaks the hydrogen bonds

DNA Replication As new strand forms follows base pairing DNA Polymerase- joins individual nucleotides to produce a DNA molecule. DNA Polymerase also “proofreads” to make sure each new strand is a perfect copy.

DNA Replication Replication is very accurate – Hydrogen bonding between base pairs more stable – Polymerase unlikely to form bonds if pairs are mismatched – Polymerase removes mismatched pairs – Proofreading results in DNA polymerase backing up and digesting linkages – Other DNA repair enzymes are involved

DNA and RNA differences Sugar in RNA is ribose RNA is single stranded RNA contains uracil in place of thymine

TRANSCRIPTION DNA language RNA language

Definition- RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA

TRANSCRIPTION DNA language RNA language 3 steps Initiation Elongation Termination

TRANSCRIPTION DNA language RNA language INITIATION – RNA polymerase bind only to regions of DNA- promoters Have specific base sequences signals to start transcribing

TERMINATION – RNA polymerase reaches the termination sequence on the strand – This causes the newly made mRNA dissociate from the DNA – Hairpin loop forms in mRNA – causing it to come off – atch?v=ztPkv7wc3yU&featur e=related atch?v=ztPkv7wc3yU&featur e=related

TRANSCRIPTION DNA language RNA language New mRNA need to be “edited” before Translation. DNA has sequences that aren’t involved in protein synthesis – introns DNA sequences that code for proteins – exons Still in the nucleus- introns are cut out of mRNA sequence Exons are spliced together Cap and tail are added to form final mRNA molecule

Translation RNA Protein Antibodies Contractile proteins- movement Enzymes Hormones- messengers for body functions Structural- Keratin, collagen, Transport proteins

Translation RNA Protein

Proteins are made by joining long chain of amino acids Codon- three consecutive nucleotides that specify a single amino acid

Translation RNA Protein

The cell uses information from messenger RNA to produce proteins 3 steps – Initiation – Elongation – Termination But first…… – mRNA is transcribed from DNA in the nucleus and released into the cytoplasm

Translation RNA Protein Initiation rRNA provides the site for translation AUG is the start codon mRNA attaches to a ribosome tRNA brings the proper amino acid to the ribosome

Translation RNA Protein Initiation rRNA provides the site for translation AUG is the start codon mRNA attaches to a ribosome tRNA brings the proper amino acid to the ribosome

Translation RNA Protein TERMINATION Stop codon is encountered the ribosome and mRNA detach and the amino acid is released

Mutations Mutations are changes in the genetic material Point mutation – changes in one or a few nucleotides. They occur at a single point in the DNA sequence. – Substitutions, insertions and deletions

Sickle cell anemia Missense mutation – base substitution that changes a single amino acid on a polypeptide sequence. Involves a mutation in the gene that code for the proteins that makeup hemoglobin.

DNA Replication DNA to Chromosomes Human-Chromosomes Human-Chromosomes PA&feature=related PA&feature=related

RNA editing