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Veterinary Bacteriology and Mycology > Bacterial Genetics > Flashcards

Bacterial Genetics Flashcards

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1
Q

What is the reason behind us resembling and differing from each other?

A

Genetics

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2
Q

How do genetics flow from generation to generation?

A

Breed true but vary in small proportions in progeny

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3
Q

Bacteria obey the laws of ________________.

A

Genetics

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4
Q

What makes up a strand of DNA?

A

Many units of either adenine-thymine or guanine-cytosine, proportions of which differ for each species

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5
Q

How does DNA replicate?

A

First unwinds at one end to form a fork, then each strand of the fork acts as a template for the synthesis of its complementary strand

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6
Q

What is semi-conservative DNA replication?

A

Two copies of the original DNA molecule are produced, each copy conserving (replicating) the information from one half of the original DNA molecule

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7
Q

How are two strands of DNA described?

A

They are antiparallel

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8
Q

What is DNA composed of?

A

Two chains of nucleotides wound together in the form of a double helix; each chain has a backbone of deoxyribose and phosphate residues arranged alternatively

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9
Q

What is attached to each deoxyribose of DNA?

A

4 nitrogenous bases:
- Purines: Adenine and guanine
- Pyrimidines: Thymine and cytosine

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10
Q

How does RNA differ from DNA?

A
  • RNA contains sugar ribose instead of deoxyribose
  • RNA has uracil instead of thymine
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11
Q

What are the 3 types of RNA?

A
  • Messenger RNA: mRNA
  • Ribosomal RNA: rRNA
  • Transfer RNA: tRNA
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12
Q

What is the central dogma of life?

A

DNA

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13
Q

What are the functions of DNA?

A
  • Carries genetic information
  • Transcribed to mRNA to form peptides that fold into proteins/enzymes
  • Storehouse for protein synthesis
  • Template for synthesis of mRNA
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14
Q

Cell function depends upon what?

A

Specific polypeptides functioning as proteins and/or enzymes

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15
Q

How do viruses differ from other life forms?

A

Contain either DNA or RNA, but not both together

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16
Q

What is a code in genetics?

A
  • A unit consisting of a sequence of 3 bases
  • Triplet A-T-C
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17
Q

What does a code make?

A

A single amino acid

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18
Q

True or false: More than one code is present for making similar sequences of AAs.

A

True, for example, AGA makes Arginine, but AGC, CGU, and CGG also code for similar AA

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19
Q

What are nonsense codons?

A

Codons such as UAA that don’t code for any AAs

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20
Q

What is a gene?

A

A sequence of DNA carrying codons specifying for particular peptides

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21
Q

How many genes does DNA contain?

A

A lot (combinations of hundreds and thousands of nucleotides)

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22
Q

What are introns vs exons?

A

Introns: several stretches of DNA that don’t appear to function as codons and occur between coding sequences of genes
Exons: coded areas interspersed by introns

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23
Q

What happens to introns during transcription?

A

They are excised by enzymes and exons are joined to form mRNA that is taken to the ribosomes

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24
Q

Describe genetic flow in eukaryotic cells.

A
  • DNA -> RNA via transcription in the nucleus
  • RNA turned from AAs to proteins via translation in ribosomes
  • Proteins have all kinds of functions within the cell or can function as enzymes
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25
What are the different flows of genetic material in prokaryotic cells?
- Protein synthesis within the cell - DNA replication between generations of cells - DNA recombination between cells of the same generation
26
Describe extra chromosomal genetic elements.
- Bacteria possess these elements that are not essential to their survival but make them more resistant to antibiotics and more survivable - Able to produce toxins
27
Where are plasmids found?
Ubiquitous in bacteria and can also be present in yeasts
28
What do plasmids encode genetic information for?
- Resistance to antibiotics - Production of bacteriocins - Enterotoxin production - Enhanced pathogenicity - Reduced sensitivity to mutagens - Degrade complex organic molecules
29
What are plasmids?
Circular DNA molecules present in the cytoplasm of bacteria that are capable of autonomous replication and can transfer genes from one cell to another and act as vectors for genetic engineering
30
What are episomes?
Integrated form of plasmid with chromosomal DNA
31
Plasmids can be _____-transmissible or _____-transmissible.
Self, non
32
Plasmids transfer the sex and drug resistance with the help of what?
Restriction end nucleases
33
What is an example of virulence plasmids?
Scalded skin syndrome
34
What is a genome?
The sum total of genes that make up the genetic apparatus of a cell; this constitutes the genotype
35
What is a genotype?
The hereditary constitution of a cell that is transmitted to its progeny
36
What is a phenotype?
The physical expression in an environment and changes according to environment
37
What is phenotypic expression?
The exhibition of different phenotypes depending on the situation
38
Give examples of different phenotypic expressions.
- Typhoid bacilli is normally flagellated, but don't have flagella when grown in phenol agar - Lactose fermentation in E. coli is dependent on b-galactosidase
39
Describe inducer enzyme.
Acts in the presence of substrate
40
Describe constitutive enzyme.
Acts irrespective of presence or absence of substrate
41
Describe the difference between genotypic and phenotypic variations.
- Phenotypic: influenced by the environment and are limited in range by genes - Genotypic: stable and not influenced by the environment
42
What are the principles of genotypic variation?
- Mutations - Transfer of genes by transformation, transduction, conjugation, or lysogenic conversion
43
How do bacteria multiply?
Asexual binary fission
44
How do mutations in bacteria occur?
Altered nucleotide sequence expresses new or altered characteristics from the previous generation
45
What are some characteristics of mutations in bacteria?
- Provide selective value to the organism - Provide evolutionary value - Acquires antibiotic resistance to grow without inhibition - Becomes more prominent
46
When does phenotypic variation occur?
When gene products are modified in response to the environment but are reversible
47
What are examples of mutagenic agents?
- UV rays - Alkylating agents - Acridine dyes - Nitrous acid
48
How does exposure to UV light result in thymine dimers?
UV rays act as a mutagenic agent and cause adjacent thymines to become cross-linked, forming a thymine dimer and disrupting their normal base pairing
49
What are the different types of point mutations?
- Silent mutation: normal protein - Missense mutation: faulty protein - Nonsense mutation: incomplete protein
50
Multiple mutations cause _________ chromosomal rearrangement.
Extensive
51
Describe a missense mutation.
Triplet code is acted upon so as to specify an amino acid different from that, normally located at a particular position in the protein
52
Describe a nonsense mutation.
Deletion of nucleotide within a gene may cause premature polypeptide chain termination by nonsense codon
53
What is transversion?
Substitution of purine for pyrimidine or vice versa in the base pairing
54
Genetic recombination occurs through what methods?
- Transformation - Conjugation - Transduction - Transposition
55
Gene transfer occurs by ___________.
Complex mechanisms
56
What are the two types of transformation?
- Avirulent (nonencapsulated) - Virulent (encapsulated)
57
What is transformation?
Transfer of genetic information through the activity of DNA
58
Describe the Griffith experiment as an illustration of transformation.
- Mice injected with live non-capsulated pneumococci and heat-killed capsulated pneumococci - Led to death of mice with isolation of live capsulated pneumococci - Means that some factor from dead pneumococci transferred to live pathogenic pneumococci
59
What is the mechanism of transformation in bacteria?
- Recipient takes up donor DNA - Recombination occurs between donor DNA and recipient DNA which results in a genetically transformed cell
60
What is conjugation?
Process by which a donor cell or male cell makes contact with another cell, the recipient or female cell
61
DNA is ____________ transferable.
Directly
62
What carries genetic information necessary for conjugation to occur?
Plasmids, only cells that contain such plasmids can act as donors, while the cells lacking a corresponding plasmid act as recipients
63
What does conjugation require?
Direct contact between donor and recipient
64
Describe the process of conjugation.
- Ability to conjugate is conferred by the F plasmid - Bacterial cells that contain an F plasmid are referred to as F+, while those that don't have an F plasmid are referred to as F- - An F+ cell and F- cell must make direct contact with each other for conjugation to occur - Results in two F+ cells
65
How does the F factor plasmid integrate into the host chromosome?
- Recombination between F factor and chromosome at a specific site on each - Insertion of F factor into chromosome results
66
Conjugation Between Hfr Cell and Recipient Cell (F- Cell) results in what?
Portion of chromosome of Hfr cell is passed to the recipient cell
67
Transduction of bacteria occurs by what?
Bacteriophages
68
Describe the process of transduction.
- Phage infects the donor bacterial cell - Phage DNA and proteins are made, and the bacterial chromosome is broken down into pieces - Sometimes during phage assembly, pieces of bacterial DNA are packaged in a phage capsid - Donor cell lyses releasing phage particles containing bacterial DNA - New phage carrying bacterial DNA infects new host cell - Recombination occurs, resulting in a recombinant cell with a genotype different from both the donor and recipient
69
What laboratory method is used in the understanding of bacterial transduction?
Phage typing

Veterinary Bacteriology and Mycology (8 decks)

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