Microbial Genetics Flashcards
Function of RNA primer in replication
creates a starting place for DNA polymerase to attach to
Describe frameshift mutation
Addition or deletion of a base causing the reading frame to shift and many amino acids are changed. Most lethal
Function of rRNA?
makes up part of the ribosomes
Which is the most lethal type of mutation?
frame shift
What processing happens to mRNA in eukaryotic cells?
initial mRNA is called pre-mRNA because it contains both introns and exons. Gets capped on the 5’ end and adenylated at the 3’ side (poly A tail) and the introns are spliced out by ribosomes to form final mRNA.
Which types of radiation are ionizing?
gamma or x ray. Results in free radicals that breaks into the chromosomes
How does UV light cause mutations?
cause pyramidine dimers between T bases next to each other. Cannot be transcribed or replicated when they exist
Define genotype and phenotype
genotype: sequence of genes, alleles
phenotype: traits expressed, proteins that are made, enzymes made in bacteria
How many chromosomes in a bacterial cell?
1
Function of tRNA
bring anticodons and amino acids to bind with mRNA
What are transposons?
jumping genes, discovered by barbara mcclintock and corn. a section of DNA moves to a new location on the chromosome without homology needed. Can insert within a gene and inactivate it (knockout mutation)Can cause frameshift-like mutations.
Define chromosomes
a long DNA molecule with part or all of the genetic material of an organism
Function and description of ribosomal subunits (APE binding sites)
A site holds the new tRNA with it’s amino acid that will add to the previous amino acid
P site- holds the growing polypeptide
E site- the exit site where the used tRNA gets released
Function of a terminator in transcription
A special sequence that signals the transcription to end and release the mRNA. Can also be stopped by an enzyme
Function of replication fork in replication
opens up the DNA and keeps it separated so that the new strands can be synthesized
Describe conjugation
A F+ bacteria creates a pilus and connects with a F- bacteria and replicates and sends it’s plasmid to the F- bacteria. Common in antibiotic resistance
What is the origin of replication?
the primer
Define mutagen
agents that induce mutations at a rate of 1-1000-100000
Describe the steps of DNA replication
- DNA is unwound+unzipped by helicase that breaks the weak hydrogen bonds between the nucleotides at the origin
- Stabilizing proteins attach to the unwound portion of the DNA to prevent it from zipping back up. This creates the replication fork
- Primase is used to synthesize a short piece of RNA (primer) that is used to prime the process
- DNA is read by DNA polymerase in the 3′ to 5′ direction, meaning the new strand is synthesized in the 5’ to 3’ direction. The leading strand new nucleotides are added by DNA polymerase in a continuous fashion towards the replication fork.
- Lagging strand is produced in pieces (okasaki fragments) away from the replication fork.
In bacteria it happens bidirectionally so that the two replicating forks are created at the same time
Compare and contrast the leading and lagging strands
leading synthesized continuously towards the replication fork
synthesized in pieces away from the replication fork
Describe how DNA is repaired
DNA polymerase proofreading
light repair- light activated photolyse breaks the pyramidine dimers
nucleotide excision repair- a piece of DNA containing a dimer is excised out and filled back in with DNA polymerase and joined back tofther with ligase. no light required.
Function of nonsense codons (stop codons)
end translation
Function of ribozymes in translation
forms the peptide/covalent bond between amino acids
Describe missense mutation
base substitution results in a different amino acid being created. Reason fo sickle cell disease
Describe the central dogma
DNA->RNA->protein
What are the recipient cells of the genetic transfer called?
recipients
Function of anticodons
complement to the codons in the mRNA
Define genetic code
groups of three bases that create codons which code for amino acids
What does semiconservative replication mean?
process results in daughter molecules that each have one strand from the parent and one new strand
Define nucleotides
building block for DNA or RNA. Consists of a nitrogen-containing base, a pentose sugar, and a phosphate. ATCGU
Compare and contrast DNA and RNA
DNA: deoxyribonucleic acid, ATCG, deoxyribose sugar, double helix
RNA: ribonucleic acid, AUCG, ribose sugar, single strand or cloverleaf or 3D
Define mutation and list common causes
a mistake or change in the sequence of nucleotides
caused by random changes and external factors
Define genetic recombination
when two strands of double stranded DNA are close in space and have similar (homologous) sequences the similar sequences can trade places.
Function of mRNA?
a temporary copy of the DNA used in translation
Function of DNA polymerase in replication
synthesizes the new strands by adding nucleotides that complement the template
Function of RNA polymerase in transcription
attaches to the promoter region and catalyzes the addition of RNA nucleotides to form the mRNA strand
What is a spontaneous mutation?
just a random mutation
Describe transformation
when bacteria absorb naked DNA fragments from their environment. Discovered by Griffith and the rats. Not all cells do this, but cells can be forced to do this by shocking them with electricity or with calcium chloride to make the competent.
Describe nonsense mutation
a base change results in a stop codon being created and protein is shorter than needed
Describe base substitution
a base is change but not deleted or added
What are the nucleoside analogs?
chemically similar to normal bases and can become incorporated into DNA and cause base pairing errors. This is how antiviral/antitumor drugs function
Describe repression
when a protein binds to the promotor region of the DNA preventing RNA polymerase from binding and turns off transcription
Describe transduction
When a bacteriophages transfers bacterial DNA from one cell to another instead of it’s own.
Function of codons (sense codons)
3 base code that codes for a particular amino acid
Function of a promoter in transcription
a special sequence in the DNA that signals for transcription to begin there
Function of DNA ligase in replication
fills in gaps in the sugar-phosphate back bone of DNA
Compare and contrast the lactose and the tryptophan operon
Lactose: Enzymes for lactose break down are not created until lactose is present which binds to the repressor and allows the transciption to take place.
Tryptophan: Tryptophan is created normally, but when an abundance of tryptophan is present it binds to the repressor and stops transcription.
Describe induction
can be turned on when an inducer is present because the inducer binds to the repressor
Define genes
a section of DNA located on a particular chromosome
Function of tRNA?
has anticodon and amino acid attached and binds with the mRNA
Function of amino acids in translation
connect together to produce proteins
Describe constitutive genes
not regulated, constant transcription, house keeping genes such as genes for glycolysis enzymes
Distinguish vertical gene transfer from horizontal gene transfer
vertical: when genomes are transferred from a parent cell to a new daughter cell
horizontal: microbes int eh same generation acquire genetic material from similar species or a different strain of the same species
