Microbial Genetics Flashcards
Define genome
the entire complement of genes on all chromosomes in an organism
Define chromosome
on double strand of DNA containing multiple genes
Define gene
segment of DNA for a functional product (gene)
Define genotype
the genetic makeup of an organism (potential properties of the cell/organism)
Define phenotype
expressed properties of an organism
Define nucleotide
the basic building block of nucleic acid that consist of a 5 carbon backbone (Ribose or Deoxyribose), a nitrogenous base (ATGC or U), and a phosphate group
Name the 2 purine nitrogenous bases
Adenine and Guanine
Name the 3 Pyrimidine bases
Thymine, Cytosine, Uracil
How do the nitrogenous bases bind to each other and what are the complementary pairings
- H bonding
- A to T or U in RNA, 2 hydrogen bonds
- C to G, 3 hydrogen bonds
Where is the nitrogenous base bound to the 5 carbon sugar of a nucleic acid
1 prime
Where is the phosphate group bound to the 5 carbon sugar back bound of a nucleic acid
5 prime
True or False, DNA strands are antiparellel and identical
False, DNA strands are antiparellel and complimentry
What are repilcation forks and what enzymes are needed
It is where short strands of DNA unwind and expose the seperated strands for DNA replication.
-Helicase, DNA gyrase, and Topoisomere= break H bonding in DNA and/or hold part of the double strand
What is the role of DNA polymerase
Inserts complementary nucleotides during DNA replication thus generating a new strand, also edits for errors when building DNA strand
What side does DNA grow in replication and why?
5 to 3 end so that excessive phospate (energy) is not included in the DNA structure
What identifies the leading strand in newly growing DNA and why is it important to know this strand?
- The 3 prime end is facing the replication fork
- This strand is continously replicated toward the replication fork, b/c of enzymetically simplicity and eas of access
What identifies the lagging strand in newly growing DNA and why is it important to know this strand?
- 5 end is towards the replication fork
- This strands grows away from the replication fork in short (Okazaki fragment)
What additional enzymes/materials are needed for lagging strand replication
- RNA polymerase and RNA primer because of lack of 3 primer end
- DNA ligase links Okazaki fragements
Why is DNA replication a semiconservative discontinous process
-It is semiconservative because in the new DNA segement one strand is newly synthesized and the other is from the parent.
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-It is discontinous because the replication of the lagging stand is produced in short fragments
True or False Uracil is only found in RNA
True it replace Thymine
What are the 3 types of RNA
- messanger
- Ribosomal
- Transfer
What does messenger RNA (mRNA) do in the cell
Carries the genetic code from DNA to the ribosome
What is a codon
A set of 3 nucleotides that specify an specific A.A
What is an Anticodon
the site on tRNA that bonds with the codon on the mRNA, it is specific to 1 AA
What does transfer RNA (tRNA) do in the cell
transports and transfers AA to the ribosome/developing peptide chain
-each tRNA is specific to 1 AA
What does ribosomal RNA (rRNA) do in the cell
RNA that is part of ribosome that facilitates peptide formation
-site where codons and anticodons come together, an where AAs are linked
Define transcription
The transfer of info in DNA to messanger RNA
What are the 5 steps of transcription
- A portion of the DNA double helix unwinds
- RNA polymerase binds to DNA at the promoter site
- Complementary RNA nucleotides are joined together by RNA polymerase
- Transcription ends when RNA polymerase reaches a termination region of the gene
- New mRNA is released and DNA re-winds
Define translation
The synthesis of a polypeptide at the ribosome specified by mRNA
What are the 4 steps in translation
- mRNA attaches to the ribosome, w/ the start codon in place
- tRNA w/ matching anticodon/AA matches to the start codon on the mRNA bring the 1st AA in place
- As mRNA codons are matched w/ complimentary tRNA anitcodons, AAs are linked together and tRNA is released
- Poltpeptide is released when the stop codon is reached.
Define constituitive genes
genes that are comstantly expressed, most genes in this category
Define and operon and describe its 4 components
Operon – related genes that are regulated as a group/series (e.g. genes which code for the enzymes of a single metabolic pathway). Can be repressible or inducible
- Repressor gene – (located in another portion of the chromosome) – codes for a “repressor” protein which can bind to the “operator” region
- b. Promoter site – region of the chromosome to which the RNA polymerase binds during transcription
- c. Operator site – region of the chromosome which controls (either permits or blocks) access of the RNA polymerase to the operon;
- d. Genes of the Operon – adjacent genes of the operon which direct the synthesis of proteins with related functions and which are regulated as a unit
Define mutation and how are they caused
Changes (substitutions, insertion or deletions) in the sequence of nucleotide bases in the inheritable genomic material (DNA or RNA),
- spontanous (mistake in genetic manufrcaturing)
- Chemicals (base analogs, nitrous acid)
- Radiation
Define Base substitution
a single nucleotide base is replaced by another
What are the 3 mutation types that abase substitution can cause
- Silent= no change in AA
- Missense= change in AA in protein, usually not significant
- Nonsense= RNA polymerase can not read the the code resulting incomplete protein
What is a frameshift mutation
It is the insertion or deletion of a nucleotide base that shifts the codon reading frame, usually causes missense
-results in major changes in RNA viruses
What inducible genes
genes that can be “turned on”
What are repressible genes
genes that can be “turned off”
Define mutation
Changes in the sequence of nucleotide bases in the inheritable genomic material (DNA or RNA)
Define recombination and reassortment
It is the gain, loss , or substitution of entire or partial gene segments to from new combinations or assortments of genes
- may result in major changes nonfunctional cells or viruses
- gene maybe entirely new or a reassortment
What is a plasmid
A small, circular, self replicating peice of DNA in bacteria
- usually not essential for growth
- often codes of Abx resistance
What is conjugation
The transfer og genetic materail between donor and recipient cells using a sex pilus
Define transformation
The direct uptake of naked DNA in solution by a bacterium
-free DNA comes from dead bacterial cells
Define transduction
The transfer of bacterial DNA by a bacteriphage
