Bacterial Genetics

Question 1

How are genes collected in a bacteria

Answer 1

On a single chromosome (circular module of double helix DNA) and on plasmids. Bacterial chromosomes are smaller then human

Question 2

DNA Characteristics

Answer 2

Bases: A,T,G and C. Double helixes antiparallel (1 read 5’-3’ and other 3’-5’). Progresses in wrappping from double stranded DNA, double helix and supercoiled DNA

Question 3

Supercoiled DNA outline

Answer 3

Twisting DNA further after double helix (done in bacteria). Makes the DNA small enough to fit into a bacterial cell. Enzyme topoisomerase are needed to wind (positive supercoil) and unwind (negative supercoil) supercoiled DNA

Question 4

DNA Gyrase Outline

Answer 4

Also known as topoisomerase 2. Negative supercoil enzyme, Inhibited by quinolones (antibiotics that kill bacteria)

Question 5

How is DNA semi-conservative

Answer 5

During binary fission DNA replicates into 2 double stranded chromosomes. Each new chromosome has 1 strand of the old DNA helix

Question 6

Helicase Function

Answer 6

Unwinds double stranded DNA to single stranded DNA during elongation

Question 7

Leading strand

Answer 7

DNA Polymerase Omega builds a new strand of DNA by combining DNA bases in the 5’-3’ direction continuously

Question 8

Lagging Strand Outline

Answer 8

DNA Polymerase Delta builds a new strand of DNA by using RNA primers to form discontinuos segments of DNA in the 5’ to 3’ direction. DNA ligase sticks these Okazaki Fragments together forming a full strand. Takes longer

Question 9

Faults in DNA Replication

Answer 9

A possible change in a base sequence can lead to different gene expression, resulting in differnt protein producton and mutation. Counter balanced by DNA omega and delta has proof reading

Question 10

Operons Outline

Answer 10

Group of genes. Rare in eukaryotes found mainly in prokaryotes. They are controlled by the same promoter/inhibitors

Question 11

What types of prokaryotic cells can transcription occur in

Answer 11

Lial

Question 12

Rifampicin Def

Answer 12

Antibiotic that prevents DNA transcription in bacteria

Question 13

How many possible codons and amino acids exists

Answer 13

64 codons and 20 amino acids. Codons groups can be redundant

Question 14

2 translation ribosomal sub units

Answer 14

30S and 50S. Complex breaks up to release proteain

Question 15

Where does tRNA enter complex

Answer 15

Acceptor (A) site

Question 16

Where does tRNA enter complex

Answer 16

Peptide (P) site

Question 17

How do antibiotics stop translation

Answer 17

Antibiotics bind to mRNA

Question 18

Where is gene expression mainly controlled

Answer 18

translation eg some bacteria begin to produce biofilm during extreme conditions, antibiotic ressistance and spore formation

Question 19

Plasmids outline

Answer 19

Circular extra-chromosomal DNA. Replicates independently and moves between cells passing on genes not necessary for functioning but are advantagous mutations (eg antibiotic ressistance)

Question 20

Nosocomial Def

Answer 20

Infections acquired in hospitals. Have a higher chance of being antibiotic resistance due to higher density and thus closer contact of bacteria for plasmid transfer. Harder to treat

Question 21

Plasmid Use

Answer 21

Genetic engineering. Gene of interest is inserted into spliced plasmid and of uptake is successful bacteria will produce beneficial proteins eg insulin

Question 22

Virulence Def

Answer 22

Production of toxins

Question 23

3 Types of Mutation

Answer 23

Base deletion, base addition and base substitution

Question 24

Silent Mutation Def

Answer 24

Change in base sequences where protein production isn’t impacted due to new codon coding for the same amino acid as the old 1 (codon redundancy) or specific amino acid change doesn’t impact protein function

Question 25

Impacts of base insertion/deletion mutation on mRNA

Answer 25

How bases are read is shift (different group of 3 codons then there was originally). This may result in a reading of a stop codon before the end of the mRNA resulting in the end of that protein's formation. This results in a non-functional (truncated protein)

Question 26

4 ways of genetic exchange between bacteria

Answer 26

Transformation, Conjugation, Transduction and Transposition

Question 27

Transformation Outline

Answer 27

Host cell takes up plasmid or DNA scraps. Most of the time DNA is degenerated (foreign material) but sometimes it is accepted and the genes are thus exptressed. Eg of natural streptococcus pnuemonia

Question 28

Conjugation Outline

Answer 28

Bacteria cells transfer tra genes (in plasmid) to eachother when in contact through conjugate pilli. Plasmid denatures in new cell and single DNA strand has a complememtary strand synthesised (cells seperate only after DNA double helix is formed in recieving cell). This can be done between all bacteria (eg gram positive and gram negative can exchange plasmids with eachother)

Question 29

Transduction Outline

Answer 29

Bacteriophage (virus) degrades DNA of host bacteria and inserts it's own. New bacteriaphages are synthesised in cell and released in lysis. Pahge then infects difffernt cell intergrating it's DNA with that cell's chromosome

Question 30

Transposition Outline

Answer 30

DNA sequences move from chromosome to plasmid in the same cell carried by transposases enzymes. can result in beneficial mutation (and passing it on) but can also disrupt genes

Question 31

2 Types of microorganism testing

Answer 31

Susceptibility (see what antimicrobials effect growth of species, long time) or molecular (analyse sample for it's DNA/RNA, faster)

Question 32

Strain Typing

Answer 32

Identifying bacteria based on their genetic code. Used for diagnosis and treatment

Question 33

Molecular Methods of Strain Typing

Answer 33

PCR, DNA probes (fluoresce after DNA binding (notes presence/absence)), Pulse Field Gel Electrophoresis (DNA finger printing) and whole genome sequencing (through computer algorithims)

Question 34

PCR Outline

Answer 34

Identification and quantification of pathogens and their mutations. Target DNA is extracted from sample, thermal DNA denaturing, primer annnelaing (changing chemical properties) and extension of primers by DNA polymerase. This

Question 35

REverse transcriptase PCR Outline

Answer 35

Used when target molecule is RNA

Question 36

PCR Advantages

Answer 36

Fast, Sensitive and Easy

Question 37

PCR Disadvantages

Answer 37

expensive and cross over of contamination

Question 38

PCR for TB

Answer 38

Detection of TB in sputum. Difficult to grow. Specific genes for early diagnosis and treatment. TB is non-culturable disease thus can't be grown in lab.