Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---



Chapter 7 – Microbial Genetics
1
...

 genome is all nucleotide sequences in a cell

2
...

 The structure contains guanine and adenine in one strand binding with cytosine and thymine
on the other
...
Describe the structure and function of plasmids
 Plasmids are small DNA molecules that can replicate on its own
o Resistance plasmids: produce genes for resistance to antibiotics
o Bacteriocin plasmids: produce protein toxins called bacteriocins that kill competitive
bacteria
o Virulence plasmids: produce pathogenic toxins
o Fertility plasmids: carry instructions for conjugation
4
...

5
...

o DNA polymerase III uses covalent bonding to join DNA template
...
This forms hydrogen bonds between
opposite bases
...

 Lagging Strand
o Primase synthesizes multiple RNA primers at multiple sites on DNA template
...

o DNA polymerase I proofreads and replaces RNA primers with DNA
...

6
...

 Genotype is the nucleotide set of genes in a genome
...




o (Structure, metabolism, etc
...


7
...

 Central Dogma: DNA is transcribed to RNA, which is translated to polypeptides
...
Describe the main steps in RNA transcription
...

 Elongation - RNA polymerase copies DNA 3’ to 5’ direction, RNA synthesizes 5’ to 3’ direction
...

 Termination
o 1) Terminator
i
...

ii
...

o 2) Rho dependent Termination
i
...
Rho protein moves toward RNA 3’ end and pushes RNA polymerase, RNA
strand, and Rho protein off of DNA
...
Describe the genetic code and identify the relationship between codons and amino acids
...

10
...
e
...

 Initiation - mRNA attaches to smaller ribosomal subunit with its start codon positioned at the Psite
...

o tRNA brings the correct amino acid ordered by the ribosome and codon at the A-site
o Ribozymes forms peptide bond between the amino acid at the P-site and at the A-site
o Previous empty tRNA leaves at the E-site (E for exit) and reload their respective amino
acid in cytosol
 Termination - ‘Release factor’ proteins notice STOP codons; ribozymes sever the growing
polypeptide from tRNA
11
...
Contains the following:
o Operator: DNA segment that controls the passage of RNA polymerase
o Promoter: Site where RNA polymerase initiates transcription
...


12
...
Give an example of
each
...

o E
...

o Allolactose is an inducer that inactivates the repressor, thus lac operon genes are free
and active
o Lac operon then codes genes for lactose catabolism only when there is a demand by
lactose
 Repressible: Repressor genes, that inhibit amino acid synthesis, are usually inactive
o When tryptophan in environment is…
i
...
Unavailable, the repressor gene is inactive and E
...
Define mutation
...

 A mutation is a change in the nucleotide base sequence(s)
...

14
...
Describe frame-shift mutations
...
No change
...

 Nonsense: A single nucleotide change causes change from amino acid codon into STOP
codon
 Frameshifts involve inserting or deleting a nucleotide to shift the sequence of codons
...
Discuss how ionizing and non-ionizing radiation cause mutations in a genome
...

 Ionizing: X-rays and gamma rays energize electrons to break free and attack other atoms
...

o This formation is called pyrimidine dimers
...
Are most mutations advantageous or deleterious?
 Mostly deleterious, because they cause non-functional proteins or abrupt transcription
...

 Mutations can be advantageous as they could help with survival, thus contribute to
evolution
...
Describe the so-called light repair and dark repair mechanisms of DNA repair
...

 Repair enzymes cut damaged DNA, then reconnected with DNA polymerase I and DNA ligase
(occurs in either light or dark)
18
...

o Example: isolating penicillin-resistant bacteria by spreading in penicillin
 Negative selection: indirect method of selecting auxotrophs from normal phenotypes
o Auxotrophs = mutant with differing nutritional requirements than normal

o

Example: for auxotroph who lost ability to synthesize tryptophan…
1
...
Define genetic recombination
...

20
...

 Vertical Gene Transfer: the transfer of genes from the parental generation to offspring
...

 Horizontal Gene Transfer: a donor cell gives part of its genome to recipient cell (may be
different species), which recipient incorporate into its own DNA, making it a recombinant
cell
...
Explain the roles of an F factor, F+ cells, and Hfr cells in bacterial conjugation
...

o Hfr cells transfer more frequently than F+ cells do
22
...

 Transduction: Can occur in either eukaryote or prokaryote
o (1) Virus injects DNA in cell, (2) virus enzymes degrade host DNA, (3) cell
synthesizes new virus with both DNA, (4) Cell lyses with daughters; transduction
occurs when virus inject original DNA into new host to combine
...
What are transposons? Contrast simple and complex
...

 The simplest transposons, called insertion sequences, consist of no more than 2 inverted
repeats and genes that code for the enzyme transposase
...

Transposition: Transposons move among locations in chromosomes in eukaryotes and prokaryotes

---