Microbio Chapter 8- Microbial Genetics Flashcards
What are genes?
Segments of DNA that code for functional products
What are the functional products?
RNA and proteins
What are the types of RNA?
rRNA
tRNA
mRNA
What is DNA?
A polynucleotide
What is a polynucleotide?
Combination of nucleotides connected through covalent bonds
Why is DNA complementary in nature?
Because of the specific base pairing
-The base sequence of one DNA strand determines the base sequence of the other strand
What are the nitrogenous base pairs?
A-T
C-G
How are paired DNA strands oriented?
Anti parallel
What is Antiparallel?
They run in opposite directions. One strand of the double helix is upside down.
Why is the sugar of the one strand upside-down?
So the paired bases can be next and close to each other
and for Stability
What is semiconservative replication?
When an original strand is conserved and 1 new one is added
What is a replication fork?
The point at which replication occurs
What is a leading strand?
Is synthesised continuously and in same direction as the replication fork
5’ - 3’
What is a lagging strand?
Synthesised discontinuously in fragments
Strand opens in 3’ - 5’ direction
What is the first enzyme used in DNA replication?
Helicase
What is Helicase?
Unwinds/unzips double-stranded DNA
What is the second enzyme used in DNA replication?
Gyrase
What is Gyrase?
Relaxes supercoiling
What is Primase?
aka RNA polymerase
-makes RNA primers from a DNA template
-Acts as a guide to know where new nucleotides need to be built
What occurs on the leading strand during replication?
DNA polymerase picks up nucleotides from cytoplasm, proof reads them and attaches complimentary bases to the strand
What occurs on the lagging strand during replication?
Primase (RNA primer) is added constantly because of the 3’-5’ direction and then RNA polymerase forms short strand of primer, then DNA polymerase adds new nucleotides in short fragments
What are the fragments of the lagging strand called?
Okazaki fragments
How is the gap filled/Okazaki fragments joined together?
Enzyme: DNA ligase
What does Semiconservative replication require?
Lots of ATP
-Supplied from nucleotides
What is Transcription?
Process of copying a segment of DNA into RNA
What is Translation?
Protein synthesis
-Process of decoding nucleic acids into proteins
Why can’t DNA polymerase read the lagging strand?
Because it is upside down
How does DNA polymerase add new nucleotides to the lagging strand?
By removing RNA primer and RNA polymerase and replaces it with DNA
What is DNA polymerase process of adding DNA in the lagging strand called?
Exonuclease activity
What is the structure of replication in bacteria?
A ring
How does DNA replicate in bacteria?
Two replications occur going in opposite directions and two new rings created (1 new 1 old)
Where do the two rings meet?
At the termination replication point
Where does replication start in bacteria?
Starts at the origin of replication
What does transcription make?
RNA
mRNA, rRNA, tRNA
What kind of RNA is new?
mRNA
What kind of RNA is recycled?
rRNA and tRNA
What is the name of where the gene begins in transcription?
Promoter
What is the name of where the gene ends in transcription?
terminator
What does RNA polymerase do in transcription?
- Copies gene
- Creates one strand (The RNA strand)
DNA vs RNA
Different sugar
# of strands: DNA- Double RNA- Single
Different bases: DNA- Thymine RNA- Uracil
Where does transcription occur in a prokaryotic cell?
Cytoplasm
Where does transcription occur in a eukaryotic cell?
Nucleus
How does RNA leave the nucleus in eukaryotes?
RNA splicing
What is RNA splicing?
Non coding sequences of RNA are removed and coding sequences join together to form mRNA
What are coding sequences called in RNA splicing?
Exons
What are non coding sequences called in RNA splicing?
Introns
What is mRNA’s role in Translation?
Carries the code from the copy of one strand of DNA in codons
What are codons?
Triplet sequences of bases
What is the sequence for the universal start codon?
AUG
What is the sequence for the stop codon?
UAG
UGA
UAA
What is a stop codon’s function?
Signal end of protein synthesis
What is rRNA’s role in translation?
A ribosomal unit where decoding happens
What is tRNA’s role in translation?
A specific tRNA pairs with its complementary sequence on the mRNA molecule so the right amino acid is inserted into the protein being synthesized
What is tRNA’s structure?
3 arms that have an anticodon
What is the longest arm of tRNA called?
Acceptor arm
What is an anticodon?
3 nucleotides that are complimentary to the mRNA codon
e.g Codon: ACG Anticodon: UGC
How are amino acids attached?
Peptide bonds
How many amino acids are universally used?
20
What is Degeneracy?
1 a.a has multiple codes which allows for some misreading/mutation in the DNA without affecting the protein made
Summarise the order of enzymes used for DNA replication:
- Helicase
- Gyrase
- DNA polymerase
- RNA primer
- RNA polymerase
- DNA polymerase
- Ligase