Chapter 12 DNA and RNA
There are four kinds of bases in DNA: adenine guanine cytosine thymine
DNA Double Helix
DNA structure http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/dna-structure.html
Chapter 12-2 Chromosomes and DNA Replication DNA makes up chromosomes!
DNA and Chromosomes DNA and Chromosomes In prokaryotic cells, DNA is located in the cytoplasm. Most prokaryotes have a single DNA molecule containing nearly all of the cell’s genetic information.
DNA and Chromosomes E. Coli Bacterium Chromosome Most prokaryotes, such as this E. coli bacterium, have only a single circular chromosome. This chromosome holds most of the organism’s DNA. E. Coli Bacterium Bases on the Chromosomes
DNA and Chromosomes Many eukaryotes have 1000 times the amount of DNA as prokaryotes. Eukaryotic DNA is located in the cell nucleus inside chromosomes. The number of chromosomes varies widely from one species to the next.
DNA and Chromosomes Chromosome Structure Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin. Chromatin consists of DNA tightly coiled around proteins called histones. DNA and histone molecules form nucleosomes. Nucleosomes pack together, forming a thick fiber.
DNA and Chromosomes Chromosomes in Prokaryotic Cells (bacteria) One circular chromosome Found in cytoplasm Chromosomes in Eukaryotic Cells Found in nucleus DNA found in several chromosomes Number of chromosomes will vary with species
DNA Replication Each strand of DNA has all the information needed to reconstruct the other half Strands are complementary and can be used to make the other strand A C T C G T A T G A G C A T
DNA Replication During DNA replication The DNA molecule separates into two strands. Produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.
DNA Replication New Strand Original strand Nitrogen Bases Growth Replication Fork Replication Fork DNA Polymerase \\loyola2\bschuller$\Biology PresentationExpress\Chapter12\Section02\Resources\ActiveArt\index.html
http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf http://www.youtube.com/watch?v=hfZ8o9D1tus http://www.youtube.com/watch?v=4jtmOZaIvS0
DNA Replication 1. Enzymes unzips DNA by breaking hydrogen bonds. Strands separate at the replication fork. Replication Fork
DNA Replication New complementary nucleotides are added to make a new strand The enzyme DNA polymerase attaches nucleotides to produce new strands. DNA polymerase proofreads each strand.
12-3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of PROTEINS. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins.
Central Idea of Genetics! DNA RNA PROTEIN Transcription Translation
RNA RNA – Ribonucleic Acid RNA DNA Ribose sugar Deoxyribose sugar Composed of a long strain of nucleotides Contains sugar, phosphate group, and nitrogen base RNA DNA Ribose sugar Deoxyribose sugar Singe-stranded Doubled-stranded Uricil Thymine
RNA Types: Messenger RNA (mRNA) – messenger from DNA to the rest of the cell Ribosomal RNA (rRNA) – make up ribosomes Transfer RNA (tRNA) – transfer amino acids to the ribosomes
Transcription The process of making RNA by copying part of the DNA sequence into a complementary RNA sequence
Transcription Requires enzyme RNA polymerase RNA Polymerase binds to DNA and separates strands RNA Polymerase uses DNA as template and assembles complementary RNA strands
Transcription
Transcription Animations http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf
RNA Editing RNA Editing The DNA of eukaryotic genes contains sequences of nucleotides, called introns, that are not involved in coding for proteins. The DNA sequences that code for proteins are called exons. When RNA molecules are formed, introns and exons are copied from DNA.
RNA Editing The introns are cut out of RNA molecules. Exon Intron DNA The introns are cut out of RNA molecules. The exons are the spliced together to form mRNA. Pre-mRNA mRNA Many RNA molecules have sections, called introns, edited out of them before they become functional. The remaining pieces, called exons, are spliced together. Then, a cap and tail are added to form the final RNA molecule. Cap Tail
Protein Review Proteins are made by joining AMINO ACIDS Each protein contains a combination of the 20 amino acids The function of the protein is determined by number and sequence of amino acids (A polypeptide is a protein!) Protein 1 Protein 2
Genetic Code The genetic code is the “language” of mRNA instructions. A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid. Each codon specifies a particular amino acid that is to be placed on the polypeptide chain.
Genetic Code RNA Sequence - Codon Sequence – U C G C A C G G U Codon Sequence – U C G – C A C – G G U Use the Amino Acid Guide to determine amino acid – Amino acid sequence – Serine – Histidine – Glycine
Translation Translation is the decoding of an mRNA message into a polypeptide chain (protein). Translation takes place on ribosomes. During translation, the cell uses information from messenger RNA to produce proteins.
Translation 1. Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome.
Translation 2. The ribosome “reads” the mRNA codon and the corresponding amino acid is brought to the ribosome by the tRNA Amino Acid Amino Acid codon
Translation 3. The ribosome forms bonds between the amino acids to form the protein Bond formed
Translation 4. Translation continues until the ribosome reaches a stop codon on the mRNA and releases the protein (polypeptide)
The BIG Picture!
Translation Animation http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf