Bacterial Genetics, Metabolism, and Structure

Question 1

*the process of heredity and variation
*starting point from which all other cellular pathways,
functions, and structures originate

Answer 1

genetics

Question 2

factor that contributes to the ability of a
microorganism to maintain viability, adapt, multiply, and
cause disease is determined by:

Answer 2

genetic composition

Question 3

THREE major aspects of microbial genetic composition

Answer 3

• The structure and organization of genetic
  material
  • Replication and expression of genetic information
  • The mechanisms by which genetic information is
  altered and exchanged among bacteria

Question 4

most common macromolecule that encodes genetic

information

Answer 4

DNA (Deoxyribonucleic Acid)

Question 5

plays an essential role in several of the
genetic processes in prokaryotic and eukaryotic cells,
including the regulation and transfer of information

Answer 5

RNA (Ribonucleic acid)

Question 6

DNA structure:

Answer 6

deoxyribose sugars connected by phosphodiester bonds (Covalent linking of bases)

Question 7

composition of an intact DNA

Answer 7

5’ (prime) phosphate

and a 3’ (prime) hydroxyl terminus (nucleotide polymers)

Question 8

direction of 2 DNA strands

Answer 8

antiparallel direction

Question 9

arrangements of strands

Answer 9

complementary:
adenine (purine)=thymine (pyrimidine) (2 hydrogen bonds)
cytosine (pyrimidine)=guanine (purine) (3 hydrogen bonds)

• thymine is replaced by uracil in RNA sequence
• hydrophobic in nature

Question 10

structural conformation of DNA

Answer 10

twisted ladder/double helix

Question 11

The three major types of RNA

Answer 11

messenger RNA [mRNA], transfer RNA
[tRNA], and ribosomal RNA [rRNA]

PLAY KEY ROLE IN GENE EXPRESSION

Question 12

important fact about RNA

Answer 12

it is NOT double stranded

Question 13

A DNA sequence that encodes for a specific product

RNA or protein

Answer 13

gene

Question 14

All the genes in an organism comprise the organism’s:

Answer 14

genome

Question 15

size of a gene and an entire genome is usually

expressed in:

Answer 15

base pairs (bp) present

Question 16

organization/arrangement of a genome into discrete elements

Answer 16

chromosome (usually arranged in a linear fashion)

Question 17

since bacteria are prokaryotes, the chromosome…

Answer 17

the chromosome is not located in a membrane-bound organelle

Question 18

arrangement of the bacterial chromosome

Answer 18

doublestranded, closed, circular macromolecule

– extensively folded and twisted (i.e., supercoiled) — in order to fit the confined space of the bacterial cell

Question 19

aside from the chromosome, bacterial genes may also be found in what extrachromosomal elements

Answer 19

plasmids and transposable elements

— not stable and may be lost during replication

Question 20

structure of plasmids

Answer 20

double-stranded, closed, circular,

autonomously replicating extrachroosomal genetic elements ranging in size from 1 to 2 kilobases up to 1 megabase or more

Question 21

other notable characteristics of plasmids:

Answer 21

• do not code for cell viability
• may also become incorporated into the
  chromosome

Question 22

pieces of DNA that move from one genetic element to another, from plasmid to
chromosome or vice versa

Answer 22

transposable elements

Question 23

other notable characteristics of transposable elements

Answer 23

• they are unable to replicate independently

* do not exist as separate entities in the bacterial cell

Question 24

two types of transposable elements

Answer 24

1) simple transposon or insertion sequence (IS)

2) composite transposon

Question 25

transposon that is limited to containing the genes that encode information required for movement from one site in the genome to another

Answer 25

simple transposon/ insertion sequence

Question 26

transposon that is a cassette (grouping of genes) flanked by insertion sequences

Answer 26

composite transposon

Question 27

this is imbedded in the insertion | sequence encodes for an accessory function, such as antimicrobial resistance

Answer 27

internal gene

Question 28

four stages of replication:

Answer 28

1. Unwinding or relaxation of the chromosome’s supercoiled DNA -- allows enzymes and cofactors to access DNA 2. Separation of the complementary strands of the parental DNA so that each may serve as a template (i.e., pattern) for synthesis of new DNA strands 3. Synthesis of the new (i.e., daughter) DNA strands 4. Termination of replication, releasing two identical chromosomes, one for each daughter cell

Question 29

the origin of replication is recognized by:

Answer 29

several initiation proteins, followed by the separation of the complementary strands of parental DNA

Question 30

site of active replication

Answer 30

replication fork (bidirectional forks)

Question 31

notable on replication forks:

Answer 31

* each replication fork moves through the parent DNA molecule in opposite directions so that replication is a bidirectional process * involves different cofactors and enzymes, with DNA polymerases playing a central role

Question 32

termination of replication happens when:

Answer 32

when the replication forks meet

Question 33

the processing of information encoded in genetic elements (i.e., chromosomes, plasmids, and transposons), which results in the production of biochemical molecules, including RNA molecules and proteins

Answer 33

gene expression

Question 34

complex steps in gene expression (in order)

Answer 34

transcription and translation

Question 35

beginning of transcription:

Answer 35

DNA -> mRNA (complementary to to gene's DNA sequence) --- only one of the two DNA strands become the sense strand - encodes for functional gene product and template for mRNA synthesis

Question 36

enzyme central to the transcription process

Answer 36

RNA polymerase

Question 37

composition of RNA polymerase

Answer 37

sigma factor and 4 protein subunits

Question 38

role of sigma factor in RNA polymerase

Answer 38

to identify the appropriate site on the DNA template where transcription of mRNA is initiated

Question 39

other name for initiation site

Answer 39

promoter sequence

Question 40

direction of transcription

Answer 40

5’ to 3’ direction

Question 41

In bacteria, the mRNA molecules that result from the | transcription process are:

Answer 41

polycistronic --- encode for several gene products

Question 42

When a cluster of genes is under the control of a single promoter sequence, the gene group is referred to as:

Answer 42

operon

Question 43

phase in gene expression that involves protein synthesis

Answer 43

translation --- responsible for protein structure and function

Question 44

genetic code consists of triplets of nucleotide | bases, referred to as:

Answer 44

codons

Question 45

Ribosomes (compact nucleoproteins) components

Answer 45

rRNA and proteins - -- central to translation - -- assisting with coupling of all required components and controlling the translational process

Question 46

three steps of translation

Answer 46

initiation elongation termination

Question 47

association of ribosomal subunits, mRNA, formylmethionine tRNA ([f-met] carrying the initial amino acid of the protein to be synthesized), and various initiation factors

Answer 47

initiation

Question 48

involves tRNAs mediating the sequential addition of amino acids in a specific sequence that is dictated by the codon sequence of the mRNA molecule

Answer 48

elongation

Question 49

arrangement wherein multiple ribosomes may be simultaneously associated with one mRNA molecule

Answer 49

polysome

Question 50

appearance of polysome

Answer 50

string of pearls

Question 51

the final step in translation, occurs when the ribosomal A site encounters a stop or nonsense codon that does not specify an amino acid (stop codons)

Answer 51

termination

Question 52

process wherein most proteins must undergo modification, such as folding or enzymatic trimming, so that protein function,transportation, or incorporation into various cellular structures can be accomplished

Answer 52

posttranslational modification

Question 53

Genetic alterations and diversity in bacteria are accomplished by three basic mechanisms:

Answer 53

mutation genetic recombination exchange between bacteria (with or without recombination)

Question 54

defined as an alteration in the original nucleotide sequence of a gene or genes within an organism’s genome

Answer 54

mutation --- arise spontaneously

Question 55

In this process, some segment of DNA originating from one bacterial cell (i.e., donor) enters a second bacterial cell (i.e., recipient) and is exchanged with a DNA segment of the recipient’s genome

Answer 55

homologous recombination ---occurs frequently

Question 56

protein that plays a central role in genetic recombination

Answer 56

RecA protein

Question 57

three mechanisms by which bacteria physically | exchange DNA

Answer 57

transformation transduction conjugation

Question 58

involves recipient cell uptake of naked (free) DNA released into the environment when another bacterial cell (i.e., donor) dies and undergoes lysis

Answer 58

transformation --- genomic DNA exists as fragments in the environment

Question 59

second mechanism by which DNA from two bacteria may come together in one cell, thus allowing for recombination ``` process is mediated through viruses capable of infecting bacteria (i.e., bacteriophages) ```

Answer 59

transduction

Question 60

process occurs between two living cells, involves cell-to-cell contact, and requires mobilization of the donor bacterium’s chromosome

Answer 60

conjugation

Question 61

considered the utilization of metabolic pathways involved in the acquisition of nutrients from the environment, production of precursor metabolites, and energy production

Answer 61

fueling