DNA & GENETICS

There are four kinds of bases in DNA: adenine guanine cytosine thymine

NUCLEIC ACIDS Nucleotide - monomer; - phosphate group, 5 carbon sugar and nitrogenous base Nucleotides covalently bind to form a nucleic acid Nucleic acids store and transmit genetic information 4 Types of nucleotides (A-T/U-C-G) = endless # of different molecules 2 Types of Nucleic Acids = DNA and RNA

Antiparallel = “head to toe”

DNA Double Helix

DNA structure

DNA makes up 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 Chromosome 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 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 ACTCGTA TGAGCAT

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 Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth \\loyola2\bschuller$\Biology PresentationExpress\Chapter12\Section02\Resources\ActiveArt\index.html

DNA Replication 1. Enzymes unzips DNA by breaking hydrogen bonds. Strands separate at the replication fork. Replication Fork

DNA Replication 2.New complementary nucleotides are added to make a new strand 3.The enzyme DNA polymerase attaches nucleotides to produce new strands. DNA polymerase proofreads each strand.

Semiconservative Replication Prior to cell division, DNA replicates itself by semiconservative replication

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 Dogma of Genetics! DNA RNA PROTEIN TranscriptionTranslation

RNA RNA – Ribonucleic Acid – Composed of a long strain of nucleotides – Contains sugar, phosphate group, and nitrogen base RNADNA Ribose sugarDeoxyribose sugar Singe-strandedDoubled-stranded UracilThymine

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 1.RNA Polymerase binds to DNA and separates strands 2.RNA Polymerase uses DNA as template and assembles complementary RNA strands

Transcription

Transcription Animations

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. The exons are the spliced together to form mRNA. Exon Intron DNA Pre-mRNA mRNA 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 - 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 – U C G – C A C – G G U Amino acid sequence – U C G – C A C – G G U 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 codon Amino Acid

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 class.unl.edu/biochem/gp2/m_biology/animation/gene/gene _a3.html class.unl.edu/biochem/gp2/m_biology/animation/gene/gene _a3.html ics/translation.swf ics/translation.swf