Bacterial Genetics

Question 1

Discovered DNA

Answer 1

FREDERICK MIESCHER (1869)

Question 2

Discovered that DNA contained phosphates, five-carbon sugars (cyclic pentose), and nitrogen containing bases.

Answer 2

PHOEBUS A.T LEVINE (1920S)

Question 3

Discovered the helical structure by x-ray crystallography

Answer 3

ROSALIND FRANKLIN

Question 4

Described the three-dimensional structure of the DNA molecule.

Answer 4

JAMES WATSON AND FRANCIS CRICK

Question 5

● Process of heredity and variation
● Ability to maintain viability, adapt, multiply, and cause disease is determined by the organism’s genetic composition

Answer 5

GENETICS

Question 6

3 MAJOR ASPECTS OF MICROBIAL GENETICS

Answer 6

1. Structure and organization of genetic material
2. Replication and expression of genetic information
3. Mechanisms by which genetic information is altered and exchanged among bacteria

Question 7

● double helical chain of nucleotides
● helix is a double strand twisted together, referred to as a “spiral staircase”
● information contained in DNA is determined primarily by the base sequence—Genetic Code
● involved in the production of RNA

Answer 7

DNA molecule

Question 8

● Is a complex combination of the following:
A. A phosphate group (PO4)
B. A cyclic five-carbon pentose sugar (deoxyribose)
C. A nitrogen-containing base, or the “steps,” either a purine or a pyrimidine

Answer 8

Nucleotide

Question 9

single-stranded and short, not double-stranded and long, and contains the sugar ribose, not deoxyribose

Answer 9

RNA molecule

Question 10

Three major types of RNA:

Answer 10

A. messenger RNA (mRNA)
B. transfer RNA (tRNA)
C. ribosomal RNA (rRNA)

Question 11

a DNA sequence that encodes for a specific product (RNA or protein)

Answer 11

Gene

Question 12

all the genes in an organism

Answer 12

Genome

Question 13

organized genome into discrete elements

Answer 13

CHROMOSOMES

Question 14

● contain a single, unpaired (i.e., haploid) chromosome
● contains the genes essential for viability and exists as a double-stranded, closed, circular macromolecule

Answer 14

BACTERIAL CHROMOSOME

Question 15

EXTRACHROMOSOMAL ELEMENTS

Answer 15

Plasmids
Transposable Elements

Question 16

double-stranded, closed, circular, autonomously replicating extrachroosomal genetic elements

Answer 16

Plasmid

Question 17

Genes encode for:

Answer 17

● products that mediate plasmid replication and transfer between bacterial cells
● products that provide a specialized function, such as determinants of antimicrobial resistance or a unique metabolic process
● Do not usually encode for products essential for viability.

Question 18

● pieces of DNA that move from one genetic element to another
● unable to replicate independently
● do not exist as separate entities in the bacterial cell

Answer 18

Transposable Elements

Question 19

2 types if Transposable Elements

Answer 19

Simple Transposon or Insertion Sequence (IS)

Composite Transposon

Question 20

contain the genes that encode information required for movement from one site in the genome to another

Answer 20

Simple Transposon or Insertion Sequence (IS)

Question 21

cassette (grouping of genes) flanked by insertion sequences

Answer 21

Composite Transposon

Question 22

● complex process mediated by various enzymes, such as DNA polymerase and cofactors
1. Unwinding of the chromosome’s supercoiled DNA
2. Separation of the complementary strands of the parental DNA
3. Synthesis of the new DNA strands
4. Termination of replication, releasing two identical chromosomes, one for each daughter cell

Process generally takes approximately 20 to 40 minutes in rapidly growing bacteria such as E. coli

Answer 22

Replication

Question 23

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

Answer 23

EXPRESSION OF GENETIC INFORMATION

Question 24

○ Synthesis of single-stranded RNA using one strand of the DNA as a template
○ DNA base sequence of the gene is converted into an mRNA molecule

Answer 24

TRANSCRIPTION

Question 25

● involves protein synthesis
● mRNA molecules is translated into specific
amino acid sequences that are responsible for protein structure and function

Answer 25

TRANSLATION

Question 26

GENETIC EXCHANGE AND DIVERSITY
Three basic mechanisms:

Answer 26

Mutation
Genetic recombination
Genetic exchange

Question 27

● alteration in the original nucleotide sequence of a gene or genes within an organism’s genome
● change in the organism’s genotype
● induced by chemical or physical factors (mutagens) or by biologic factors

Answer 27

Maturation

Question 28

● segment of DNA originating from one bacterial cell (donor) enters a second bacterial cell (recipient) and is exchanged with a DNA segment of the recipient’s genome
● pieces of DNA are usually have extensive similarities in nucleotide sequences
● involves a number of binding proteins

Answer 28

GENETIC RECOMBINATION

Question 29

Three mechanisms of genetic exchange

Answer 29

TRANSFORMATION
Transduction
Conjunction

Question 30

● Cells that can take up naked DNA
● Example: Streptococcus pneumoniae, Neisseria
gonorrhoeae, H. influenzae

Answer 30

Competent

Question 31

Type of transduction where bacterial DNA may be randomly incorporated with viral DNA

Answer 31

GENERALIZED TRANSDUCTION

Question 32

Type of transduction that is incorporated along with adjacent viral DNA

Answer 32

SPECIALIZED TRANSDUCTION

Question 33

● transfer of genetic material from a donor bacterial strain to a recipient strain
● Occurs between two living cells, involves cell-to-cell contact, and requires mobilization of the donor bacterium’s chromosome
● Plasmids and transposons—transferred by conjugation

Answer 33

Conjugation