Microbial Genetics Flashcards
What are the three components of a nucleotides?
- Phosphate
- 2, Deoxyribose
- Nitrogen Containing Base
What is the basic subunit of DNA?
Nucleotides are the subunits of DNA.
What kind of bonds hold the components of a nucleotides together?
Covalent bond
What kind of bonds hold the two strands of a double helix together?
Hydrogen bond
What component of a nucleotide specifies the genetic information?
Genome
What are the four nitrogen-containing bases found in the DNA?
Adenine, Guanine, Thymine, Cytosine
What is complimentarily what to what?
Adenine to Thymine
Cytosine to Guanine
What is anti-parallelism?
Two strands of DNA are always oriented in opposite directions.
What is semi-conservative replication?
Each cell receives one parental strand and one daughter strand.
What enzymes are involved with DNA replication?
DNA Helicase, DNA Polymerase, DNA Exonuclease, and DNA ligase
What are the three kinds of RNA?
tRNA, mRNA, rRNA
What is the difference between DNA and RNA?
- RNA is similar to DNA, except RNA is single stranded helix, has ribose sugar, has URACIL, and it is shorter than DNA (1000 nucleotides in length).
- DNA has a double helix that is intertwined with 5 base pairs per turn. Always antiparallel. 2 strands of DNA are always oriented in opposite directions.
What are the 3 kinds of RNA and what are their functions?
- rRNA (ribosome): part of ribosome (60% of a ribosome is made of RNA, the rest is made of protein).
- tRNA (transfers): carries amino acids to the ribosome during protein synthesis. tRNA is also known as anti-codon. It is bivalent with a so called clover leaf shape. Picks up and transfers 1 of 20 possible amino acids to the ribosome.
- mRNA (messenger): a complimentary strand of RNA equal in size to 1 gene (normally 1000 nucleotides). Codon - coded information from DNA. (bound for the ribosome.) The cells genetic plan contained in DNA is transcribed into a complimentary base sequence. mRNA is a blue print of DNA, a transcript, or a code.
What is the central dogma of biology?
DNA (replication) –(transcription)–> mRNA –(translation)–> protein
What enzyme performs transcription?
RNA polymerase.
What is the product of transcription?
The product of transcription of DNA: RNA
What are the three steps of translation? (Briefly summarize all steps)
Step 1) Initiation - mRNA bumps into the small subunit and triggers the two ribosomal subunits to bind together. The first tRNA anticodon (UAC) carries the the amino acid methionine hydrogen bonds with the codon AUG on mRNA.
Step 2) Elongation - The second tRNA hydrogen bonds to the second code word on mRNA. A peptide (covalent) bond forms between the two amino acids. The first tRNA leave. The enzyme translocase moved the ribosome down one code word of mRNA at a time. This repeats 333 times.
Step 3) Termination - 1 of 3 possible stop codons is reached. The last tRNA falls away and the two ribosomal subunits fall apart. Enzyme is complete with 333 amino acids and released into the cytoplasm.
What is the production of translation?
Protein.
What is the genetic code? How many nonsense codons? How many sense codons?
Genetic codes are the 64 codons. There are 61 sense codons for 20 amino acids, and 3 nonsense codons that are stop codons.
How many bases are in one code word of the genetic code?
there are 3 bases in one code word of the genetic code.
Where does the protein synthesis take place?
In the ribosome.
What antibiotics block protein synthesis and by what mechanism?
Tetracycline and streptomycin. Their mechanism is a protein synthesis inhibitor (to block protein synthesis).
Where does the lac repressor binds in the absence of lactose in the lac operon?
In the operator sites.
What chemical process causes the epigenetic shut off of a gene?
Methyl Functional Group (CH3)
What are the 3 examples of point mutation?
Silent Mutation
Missense Mutation
Nonsense Mutation
What is the probable effect on the amino acid sequence after a silent mutation?
No change in amino acid or enzymes.
What is the probable effect on the amino acid sequence with the nonsense mutation?
Result incomplete defective enzymes.
What is the probable effect on amino acid sequence with missense mutation?
Changes amino acid. Usually no effect, however, if in the active site, it will cause defective enzyme.
What happens to the DNA sequence in a frame-shift mutation?
Addition and deletion of one or more bases on the DNA due to chemical or physical mutagens.
What are the three categories of chemical mutagens and provide one example of each?
- Nitrous Acid - examples: found in smog and form in the body when eating smoked meat. Alters adenine so it pairs with cytosine.
- Alkylating agents - examples: Formalin, Nitrogen mustard, and ethylene oxide. Reacts with guanine causes mispairing.
- Nucleoside analogs - ex: AZT - a modified sugar that substitutes for thymine. Another example is bromouracil.
- Intercalating agents - ex: aflatoxin - is a chemical produce by the peanut and grain modl. (aspergillus flavus [fungus]).
What are the 2 examples of physical mutagens?
- Non-ionizing raditation - causes formation of Thymine to Thymine dimers. Ex: UV light @ 260 nm.
- Ionizing radiation - breaks DNA forms “free radicals” leading to mutation. Ex: X-rays, Gamma Rays (from stars and nuclear blasts), Radon (natural in the enviroment), and Alpha rays (inhaling dust containing radioactive fullout).
What genus and species of bacteria is famous for transformation?
Streptococcus pneumoniae
In what two ways can this bacteria benefit from transformation?
1) Capsule Formation
2) Penicillin resistance
Briefly describe conjugation?
Conjugation is like a mating process between a donor F+ and an F- recipient cell. It occurs in Gram Negative (-) enteric bacteria (family Enterobacteriace) Conjugation was discovered by Lederberg and Tatum in 1946. F+ bacteria transmit a copy of the plasmid into F- bacteria, where F- becomes a F+. Plasmid carries genes that are nonessential life of bacteria. Unusual proteins are synthesized by plasmid genes, such as gene for pili, gene for plasmid replication enzymes, and genes for antibiotic resistance. (example would be Klebsiella Pnemoniae Carbapenemase [KPC])
What family of bacteria conjugate and where in the body they are located?
Enterobacteriace. Found in the human intestines.
Provide three functions of genes located on plasmids?
Gene Pili (Sex pilus)
Gene for plasmid replication enyzmes
Genes for antibiotics resistance (r-factors)
What does the acronym Hfr stands for?
High Frequency Recombination
Why is antibiotic resistance more of a problem with Hfr bacteria?
It is able to be passed down during binary fission every time the cell divides. Antibiotic resistance develops very quickly.
What occurs when an Hfr mates with a F- cell?
When the Hfr mates with F- bacteria, only the bacterial genes cross, not the plasmid genes. (Genetic diversity results in this case due to Hfr).
What microbe is found on the skin while performing transposition, and what is the acronym for its famous antibiotic resistant strain?
Staphylococcus Aureus is found on the skin while performing transposition. The acronym for the antibiotic resistant straing is MRSA (Methicillin resistant Staphylococcus Aureus).
Compare and contrast generalized and specialized transduction: name of the virus, mechanisms, and outcome for the recipient E. coli.
Generalized
•T2ø
•Lytic Cycle
•Random Packaging
•Recombination
•Genetic Diversity
Specialized
•Lambda Phage (λφ)
•Lysogenic/Stress = Lytic
•Specialized galactose gene
•recombination
•To metabolize lactose
What STEM cell research technique uses de-nucleated ovum inoculated with the somatic cell DNA for an individual needing transplant or replacement tissues?
Somatic Cell Nuclear Transfer (SCNT)
What is the function of phosphate group?
To be a structural part of DNA.
What is the 2 Deoxyribose?
It is a 5-carbon sugar that functions as a part of the DNA back bone. 2 Deoxy means “without oxygen” on the number 2 carbon atom.
What is the nitrogen base for?
To express the genetic information.
What are the two double ring of purines?
Adenine and Guanine
What are the two single ring of pyrimidines?
Thymine and Cytosine
What is a DNA?
DNA is deoxyribonucleic acid. It is made up of subunits called nucleotides, such as phosphate group, 2 deoxyribose, and Nitrogen base. Those three components are linked together with a covalent bond.
