Microbial Genetics (8.1-8.3) Flashcards
Where are the genomes located in bacteria?
Chromosomes or plasmids
Where are the genomes located in viruses?
The nucleocapsid
What are the structural features of DNA? What 3 things makes that structural feature?
Made of Nucleotides
- Phospate
- Deoxyribose (FIVE CARBON SUGAR)
- Nitrogenous base
What are the two groups of Nitrogenous bases?
pyrimidines and purines
What are the pyrimidines?
T (Thymine), C (cytosine) and U (uracil)
What are the Purines?
A (adenine), and G (guanine)
How do nucleotides covalently bond to each other?
Through a sugar- phosphate linkage. The 5’ carbon on the deoxyribose connects to a phosphate group that connects to the 3’ carbon to form a strand.
What are the nitrogenous base pairs and how many Hydrogen bonds do they have?
- Adenine (A) pairs with Thymine (T) = 2 pairs
- Guanine (G) with Cytosine (C) = 3 pairs
DNA is a _____ helix and has an ______ arrangement.
Double ; antiparallel
Overall DNA replication process is called __________ replication. Why?
semiconservative ; because there’s a parent strand that creates a complementary strand. (one original strand and one new strand on both new double helixes)
Break down the process of DNA replication. Include all 3 enzymes.
- Topoisomeras unwinds the DNA helix
- Helicase breaks the hydrogen bonds holding the two strands together, creating two separate strands
- Polymerase (III) Adds the nucleotides that pair with the nucleotides on the leading strand (the one that goes 5’ to 3’) because polymerase can only builds a 5’ to 3’ strand.
The strand that’s originally in the 3’ to 5’ is called the lagging strand because polymerase has to keep moving in order to build a strand in the 5’ to 3’ direction which is where primers help tell them where to stop and start. This creates Okazaki fragments DNA polymerase (I) removes the primers and closed gaps and the fragments are joined together to make a strand by DNA ligase.
At the end of DNA replication you have TWO double helix molecules.
Why are A (Adenine) & T (Thymine)’s bond important in DNA replication?
They only have two hydrogen bonds so it’s easier to split the double helix.
What direction is the leading strand synthesized in?
5’ to 3’
On the ____ strand, DNA polymerase synthesizes a few bases at a time in the direction _____ from the replication fork
lagging ; away
The enzyme that then joins the fragments together to create the strand is called
DNA ligase
True or False
Bacteria replicates DNA at a pace of 750 bases per seconds at each fork (fast) which makes mutations more likely to occur
true
What is transcription?
when DNA is used to create RNA (mRNA)
Explain the process of transcription. when does it stop? Can include the 3 steps.
Initiation: RNA polymerase binds to the template strand that goes (5’ (near the replication fork) to 3’ at the end away from the replication fork
Elongation: and creates an mRNA strand that goes 5’ to 3’ towards the replication fork
Termination: Keeps going until RNA polymerase reaches the TERMINATION REGION
What is a regulatory RNA?
List the 4 examples of one.
They are important regulators of gene expression in bacteria. (They regulate transcription and translation.) Examples: -Micro RNAs - Anti-sense RNAs -Riboswitches - Small interfering RNAs
What is translation?
Making proteins from mRNA directions
What are the STOP CODON nucleotides?
UAA, UGA, UAG
Explain the process of transcription + translation
Transcription: mRNA is made from a DNA strand
Ribosomal subunits (50S + 30S) come together to hold the mRNA and tRNA. The ribosome scans the mRNA inn a 5' to 3' direction.
THEN
tRNA anticodons match the right nucleotides to the mRNA codons and creates the amino acids
What is a codon?
A group of three nucleotides that dictate which amino acid is added to the growing peptide chain
What is a wobble ?
The first two nucleotides that are required to encode the correct amino acid.
permits some variation or mutation without altering the message.
What is the START CODON nucleotides?
AUG
In a ribosome, what does the pyrimidine (U) uracil bind to?
(A) Adenine
What is the anticodon for AUG
UAC
What is the difference between DNA and RNA?
RNA - ribose, single stranded, has uracil instead of thymine, can form secondary and tertiary levels
DNA - deoxyribose, double stranded
What are Operons?
A genetic operational unit that regulates metabolism by controlling mRNA production.
What is a catabolic operon?
CODE FOR enzymes that can be turned on (induced) when the substrate (nutrient) to create that product is in the area.
What is a repressible operon? / anabolic
CODE FOR enzymes that are usually on but can be turned off (repressed)
Explain the example of the LAC OPERON
the repressor attaches to an operon when lactose is not present.
when lactose is introduced into the environment, it turns the operon on by binding to it which changes the shape of the operon causing the represor to dislodge from the operator segment of the DNA.
The RNA polymerase can now bind to the promoter.
Enzymes are created in the ribosome.
As lactose depletes, it can repress the repressor anymore so it returns back to inhibiting the operon.
What are the parts of an operon?
Regulator, promoter, and operator
What are the 3 events in translation elongation?
- The ribosome shifts from one Condon on the mRNA to the next
- A tRNA delivers the next amino acid in the sequence
- Amino acids are joined by polypeptide bonds
Protein synthesis is more efficient in bacteria than in eukaryotes for the filling reasons EXCEPT:
- BACTERIAL TRANSCRIPTION ADN TRANSLATION ARE SIMULTANEOUS
- bacterial mRNA contains no introns ( a segment of DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.)
- Bacterial ribosomes are 70S rather than 80S
Bacterial ribosomes are 70S rather than 80S
The type of RNA strand that contains codons representing amino acids of the polypeptide is the ____
mRNA
One reason protein synthesis is more efficient in bacteria than in eukaryotes is because bacterial _____ and _____ occur simultaniously
transcription and translation
Several codons code for the same amino acid, which is called the ____ of the genetic code.
redundancy
During protein synthesis, tRNA carries _____ to the ribosome
amino acids
To initiate transcription, RNA polymerase binds to the _____ region of the DNA
promoter
What do you call the complex that includes multiple ribosomes on a single transcript?
polyribosomal
