10/19/2015 UNIT 6: GENETICS (CH 7) & BIOTECHNOLOGY (CH 8) GENETIC PROCESSES: MUTATIONS GENETIC PROCESSES: HEREDITY

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1 GENETIC PROCESSES: HEREDITY Heredity definition: The passing on of information from an organism to its offspring (through genes) Chromosome definition: Typically a circular (in prokaryotes) or linear (in eukaryotes), threadlike molecule of DNA UNIT 6: GENETICS (CH 7) & BIOTECHNOLOGY (CH 8) SC2730 Microbiology Genes definition: The basic unit of heredity; a linear sequence of nucleotides (bases) of DNA that determines a certain characteristic. GENETIC PROCESSES: MUTATIONS Centromere Sister chromatids Chromosome Histone Supercoil within chromosome Continued coiling within supercoil Mutation definition: A permanent change in DNA which can change the sequence of DNA bases When the mutated DNA is transmitted to a daughter cell, it can be different from the mother cell in one or more characteristics. WHY: Because all the info for the structure and functioning of an organism is found in DNA (directions on what proteins need to be made) DNA GENETIC PROCESSES: HEREDITY GENETIC PROCESSES: INFORMATION TRANSFER Bacterial cells typically have 1 chromosome The E.coli genome is made of about 5 billion bases that code for at least 4288 proteins How is information transferred from DNA into protein synthesis? 1. Replication: DNA makes a copy of itself 2. Transcription: DNA makes a copy of RNA 3. Translation: RNA links amino acids together to make proteins 1

2 DNA STRUCTURE - is composed of many small monomers called nucleotides Nucleotides are made up of 3 parts: 1. a phosphate 2. deoxyribose sugar 3. nitrogen containing base Hydrogen bonds between the bases hold the strands together Bases in DNA Nitrogenous Bases in DNA 1. Adenine (A) 2. Guanine (G) 3. Cytosine (C) 4. Thymine (T) WHAT MAKES UP DNA? Sugar in DNA Deoxyribose Strands in DNA TWO - Fathers of DNA: DNA structure discovered by James Watson & Francis Crick DNA REPLICATION Location: Nucleoid region Purpose: DNA information is copied so that it can pass on information to the daughter cell REPLICATION: STEP #1 a. An enzyme called DNA helicase unzips the parent strand by breaking the hydrogen bonds. b. This causes the complementary base pairs to separate. *Making replication bubbles and forming a replication fork. replication bubble REPLICATION: STEP #2 a. An enzyme called DNA polymerase gathers free nucleotides floating in the nuclear region; it also proofreads for mistakes. b. DNA polymerase pairs the free nucleotides w/its complementary base partner, following the base pair rule (A T, C G). REPLICATION: STEP #3 a. An enzyme called DNA ligase binds the newly attached free nucleotides. b. DNA ligase acts as glue on the new strand of DNA being formed Pairing of the bases occurs in opposite directions simultaneously. In humans, DNA polymerase adds 50 nucleotides per second. In bacteria, DNA polymerase adds 1000 nucleotides per second. 2

3 WHAT IS THE END RESULT? Two identical strands of DNA are now present in the nucleus. *Each newly synthesized DNA has one parent (old) strand and one daughter (new) strand of DNA. *This is called semi-conservative replication. DNA COMPLEMENTARY PRACTICE 1. CATTAGCTG GTAATCGAC 2. TGCACTGA ACGTGACT 3. ATCGGCAT TAGCCGTA 4. AATCTCCG TTAGAGGC BRAIN CHECK 1. How many chromosomes are found in a typical bacterial cell? A. 1 B. 2 C. 16 D What enzyme binds DNA sequences together during replication? A. DNA helicase B. DNA ligase C. DNA polymerase 3. What enzyme unzips DNA during replication? A. DNA helicase B. DNA ligase C. DNA polymerase 4. What enzyme adds DNA bases & proofreads the additions during replication? A. DNA helicase B. DNA ligase C. DNA polymerase WHAT IS PROTEIN SYNTHESIS? *Protein synthesis is the building of proteins following the instructions of DNA. *Why do we need proteins? What is protein synthesis? Is protein synthesis important? What is RNA? PROTEIN SYNTHESIS Where is RNA found? Is RNA similar to DNA? What is translation? *The instructions of DNA are written by the order of the bases. Example of instructions on DNA: A - G - A - T - C - T 3

4 PROTEIN STRUCTURE A protein is made up of a chain of monomers called amino acids in a particular order, held together by peptide bonds. EXAMPLE OF PROTEIN: A CHAIN OF AMINO ACIDS Alanine Phenylalanine Glutamine Valine Proline Lysine NAMES OF AMINO ACIDS Actual Sequence and names of AMINO ACIDS In Blood (Hemoglobin) WHAT IS REQUIRED FOR PROTEIN SYNTHESIS? 1. DNA 2. mrna 3. rrna (ribosomes) 4. trna WHAT IS RNA? Full Name: Ribonucleic acid *It is the nucleic acid responsible for three things in protein synthesis: 1 copying instructions from DNA 2 carrying the instructions for making proteins to the ribosome 3 putting the protein together on the ribosome WHAT MAKES UP RNA? Bases in RNA Nitrogenous Bases in RNA Sugar in RNA Deoxyribose Strands in RNA ONE 3 Types of RNA 1. Messenger RNA (mrna) 2. Ribosomal RNA (rrna) 3. Transfer RNA (trna) 1. Adenine (A ) pairs with Uracil (U) 2. Guanine (G) 3. Cytosine (C) 4. Uracil (U) In base pairing, thymine (T) is replaced by uracil Function: plays a role in making proteins mrna trna rrna 4

5 MESSENGER RNA (MRNA) Function: 1. Goes to DNA and makes a copy of DNA using RNA bases. 2. Takes the copy to the ribosomes. 3. Contains the codon (group of 3 bases on mrna) Major structural part of the ribosome where protein synthesis occurs. RIBOSOMAL RNA (rrna) Made of 2 subunits that join together around mrna, causing transcription to start. STEPS IN PROTEIN SYNTHESIS Step I Transcription Step 2 Translation TRANSFER RNA (TRNA) Function: 1. carries amino acids to mrna at the ribosome to make the protein. 2. contains anticodon (3 bases that match up w/the codon on mrna) STEP 1: TRANSCRIPTION STEP 2: TRANSLATION Location: in the cytoplasm Purpose: to copy the DNA message (order of bases) into mrna. Events: 1.) DNA is unwound and DNA helicase unzips DNA strand. 2.) RNA polymerase reads the complementary base and adds the new RNA nucleotides along the DNA strand to create a single strand of mrna. 3.) mrna is made and goes out of the nuceloid region to the ribosome. Location: in the cytoplasm, on the ribosome. Purpose: to convert the instructions of mrna (order of bases) into amino acids, to make proteins. 5

6 STEP 2: TRANSLATION Events of translation: 1.) The first three bases of mrna (codon) join the ribosome. AUG is the start codon 2.) trna brings the amino acid down to the ribosome. The three bases on trna, or the anticodon, match the complementary bases on mrna. Events of translation: 3.) Each trna has an AMINO ACID that is determined by its anticodon. Ex: codon (AUG) Amino Acid - methionine STEP 2: TRANSLATION 4.) The amino acids are joined by polypeptide bonds. 5.) The resulting chain of amino acids are called a PROTEIN. SPECIAL CODONS Process Information for process Product Type of Base Pairing Required Start codon always AUG (methionine) in eukaryotes and either GUG or UUG in bacteria; signals the start of translation Terminator or stop codon - signals the end of a translation (like a period to a sentence) Replication (synthesis of DNA) Transcription (synthesis of RNA) Translation (synthesis of protein) Entire length of double helix DNA DNA with DNA Small part of a DNA strand mrna DNA with RNA mrna Protein mrna with trna to AA s/protein BRAIN CHECK 1. What type of RNA carries and transfers amino acids from the cytoplasm to the ribosome for placement in the synthesis of a protein? A. messenger B. ribosomal C. transfer 2. What type of RNA carries the genetic information required for protein synthesis? A. messenger B. ribosomal C. transfer PRACTICE WITH AMINO ACIDS 6

7 MUTATIONS What is a mutation? Any change in the DNA sequence (substitution, insertion, or deletion) Point mutation Frameshift mutation MUTATIONS OOOPS! How can mutations happen? 1. Spontaneous mistakes in base pairings 2. Induced mutations by mutagens (agents that cause mutations) radiation chemicals high temperatures SPONTANEOUS MUTATIONS Point mutation: a change in a single base because of nucleotide substitution Correct DNA Correct mrna Correct AA GAG CTC CUC Leucine Frameshift mutation: when there is an insertion or deletion of one or more bases Correct DNA: ATA CCG TGA TAT GGC ACT Correct mrna: UAU GGC ACU Correct amino acids: Tyrosine Glycine Threonine Extra inserted base SHIFTS how we read the codons (3 bases), which changes the amino acids Point mutation mutated mrna Wrong AA GCG CTC CGC Arginine A should pair with T, but instead C is mismatched to T Frameshift mutation ATA GCC GTG A in DNA: TAT CGG CAC T Mutated mrna: UAU CGG CAC U Wrong amino acids: Tyrosine Tryptophan Histadine Frameshift Mutations: Insertions Frameshift Mutations: Deletions 7

8 MUTATIONS o Point mutations aren t always harmful because it affects one codon (amino acid) and the new codon made may not cause the protein to function incorrectly. However, if it codes for a stop codon in the middle of a protein being made, it may be lethal. o Frameshift mutations can have catastrophic effects on genes because ALL the codons that follow the shift will be altered, not just one. o Mutation repair: Proofreading enzymes are able to repair some damages to DNA BRAIN CHECK 1. A frameshift muation occurs following the: A. Insertion of one base or more B. Deletion of one base or more C. Both of these 2. In a mutation, a daughter cell would inherit which of the following changes from the parent cell? A. A change in protein D. A change in trna B. A change in mrna E. A change in DNA C. A change in rrna GENE TRANSFER o Gene transfer: the movement of genetic information between organisms; increases genetic diversity o Donor cell: transfers the genes PCR? DNA Recombination? BIOTECHNOLOGY o Recipient cell: receives the genes o Recombination: combining of genes (DNA) from 2 different cells; the resulting cell is referred to as recombinant TYPES OF GENE TRANSFER IMPORTANCE OF LGT o Vertical gene transfer (VGT): the transmission of genes from the parental generation to offspring via sexual or asexual reproduction. o Lateral gene transfer (LGT): the transfer of genes between organisms in a manner other than traditional reproduction. o Thought to be the primary reason for bacterial antibiotic resistance o Plays an important role in the evolution of bacteria that can degrade unique compounds such as human-created pesticides o Plays a role in the evolution, maintenance, and transmission of virulence 8

9 BINARY FISSION ISN T ALL THERE IS Before 1920, scientists thought that bacteria only reproduced through asexual reproduction via binary fission but now we know of other methods: 3 other mechanisms: Transformation Transduction Conjugation TRANSFORMATION o Transformation: the uptake of naked DNA (DNA without associated cells or proteins because of cell lysing) during cell growth (they pick up pieces of DNA from other dead bacterial cells) o Only cells that are competent can do this. This means that the cell has a special protein called a competence factor. This protein gives the growing cell the ability to take up extra DNA from the environment. o TRANSFORMATION SIGNIFICANCE Occurs naturally in nature (maybe after an organism decomposes into the environment) o Occurs in the lab by: Heat Cold Chemicals Strong electric field ** Used to study the location of genes and effects of different DNA on already existing DNA (recombinant DNA) TRANSDUCTION o Transduction: process in which DNA is transferred from one bacterium to another by a bacteriophage o Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome o Future use: working on correcting genetic diseases by direct modification of genetic errors CONJUGATION o Conjugation: the transfer of the plasmid (genetic material) between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells o Plasmids: small, circular extrachromosomal DNA molecules o F+ cells: contain F plasmids (F = fertility); called the donor cell or male cell o F- cells: lack F plasmids; called the recipient cell or female cell CONJUGATION o DNA is transferred when the F+ cell makes a mating bridge by extending an F pilus (sex pilus or conjugation pilus) which attaches to the F+ cell. o The genetic information transferred is often beneficial to the recipient. Benefits may include antibiotic resistance, pollutant tolerance, or the ability to use new metabolites Occurs more than transformation & transduction so it makes the most contribution to genetic diversity 9

10 BRAIN CHECK 1. How does transformation differ from transduction? 2. Why does conjugation have such an impact on genetic diversity? GENETIC ENGINEERING Definition: purposeful manipulation of genetic material to alter the characteristics of an organism in a desirable way Major types: 1. Gene amplification 2. Recombinant DNA technology GENE AMPLIFICATION o Polymerase chain reaction (PCR): used to amplify a single copy or a few copies of a piece of DNA to generate thousands to millions of copies of a particular DNA sequence o Increasing antibiotic production & the production of amino acids, vitamins, & nucleotides RECOMBINANT DNA TECHNOLOGY Used in several ways: Manipulate DNA in vitro Recombination of another organism s DNA with bacterial DNA in a phage or plasmid Cloning of bacteriophages or plasmids Vectors (self-replicating carriers) are used to do this: 1. DNA from pro-/eukaryotic cells is removed cells 2. Cut into small pieces using restriction enzymes 3. DNA is incorporated into the vector by DNA ligase 10