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Micro B2 > Microbe Genetics > Flashcards

Microbe Genetics Flashcards

1
Q

the entire complement of genes on all chromosomes normally found in an organism;
the hereditary information

A

Genome

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2
Q
  • one entire double-strand of DNA containing multiple genes [The chromosome is
    always DNA, except in RNA viruses.] [Also referred to as “nuclear material” or “nucleic acid”.]
A

Chromosome

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3
Q
  • a segment of DNA that contains the genetic code (blueprint) for a functional product (e.g.
    code for a specific protein)
A

Gene

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4
Q

The genetic code is translated into proteins for structural, catalytic, or regulatory functions
within the cell with the aid of

A

messenger RNA and ribosomes

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5
Q

Genetic code for each protein is carried as a sequence of ____
macromolecule

A

nucleotide molecules in the nucleic acid

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6
Q

Genes contain

A

instructions for making proteins

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7
Q

Composition of Nucleic Acids (nucleotide)

A

5-carbon sugar – either Ribose or Deoxyribose

nitrogenous base (Bound to 1`)

phosphate group (bound to 5` carbon)

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8
Q

Nitrogenous base

A

Purine (adenine, guanine)

pyrimidine (thymine, cytosine, uracil)

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9
Q

Adenine binds

A

Thymine (or uracil)

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10
Q

Guanine binds

A

cytosine

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11
Q

5 is oriented to lateral on one side and 3 is the lateral portion on the opposite side…

A

makes sense?

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12
Q

Adds next nulceotide to 3`C side ONLY

A

DNA polymerase

will not add to 5`C

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13
Q

antiparallel concept

A

antiparallel – the two strands run in opposite directions; i.e. the nucleotide
of the 3’ end of one strand pairs up with the nucleotide of the 5’ end of the adjacent
strand. Strands are not identical, but are complementary.

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14
Q

Strand Direction

A
  • the end on which no phosphate is bound to the 3’ carbon of the
    sugar is called the 3’ end; the end in which the phosphate is bound only to the 5’ carbon
    is called the 5’ end
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15
Q

form where short lengths of double-stranded DNA helix unwind, thus exposing the separated strands. Unwinding (and rewinding) is due to action of enzymes such as helicase, DNA gyrase, and topoisomerase which break the hydrogen
bonds between bases and/or hold part of the strand stable.

A

Replication forks (think of a zipper)

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16
Q

binds to DNA and inserts complementary nucleotides thereby

generating a new strand

A

DNA polymerase

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17
Q

Unwinding (and rewinding) is due to action of

enzymes such as

A

helicase, DNA gyrase, and topoisomerase

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18
Q

DNA “opening” (4-step sequence)

A

A short length of “parental” DNA unwinds

Exposes the separated strands

Creates a replication fork

Due to action of helicases, DNA gyrase, etc.

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19
Q

DNA polymerase ____ with accuracy of about 1 error in a billion base
pairs replicated

A

edits for errors

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20
Q

“Leading” strand is the _____ strand having the 3’ end of the exposed
nucleotide “facing toward” (“leading into”) the replication fork

A

newly growing (SEE PAGE 4 on PDF)

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21
Q

The newly developing strand grows toward the

A

replication fork, i.e. “leads into” the

fork

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22
Q

The leading strand is ____ because of enzymatic simplicity and ease of
access to the molecule

A

continuously replicated

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23
Q

______ is the strand having the 5’ end of the exposed nucleotide facing
toward the replication fork

A

“Lagging” strand

lags by a fraction of a second

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24
Q

The newly developing “lagging” strand grows _____, which is
accomplished by replicating short fragments, then connecting them together to
form a new complementary strand

A

away from the replication fork

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25
Q

_____ are needed to initiate strand growth in the

absence of a nucleotide having a 3’ binding site

A

RNA primer and RNA polymerase

i.e., for the lagging strand’s exposed 5`C

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26
Q

After a RNA primer is in place, thus providing a 3’ site, then ______. However, DNA polymerase cannot join the final
nucleotide of the new fragment to the existing strand because it cannot facilitate
linking to both 3’ and 5’ binding sites

A

DNA polymerase
takes over the replication and continues to within one nucleotide of the existing,
previously generated strand

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27
Q

facilitates linkage of a nucleotide to both 3’ and 5’ binding
sites simultaneously, inserts a nucleotide to join the newly replicated fragment with
the existing strand

A

DNA ligase

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28
Q

The replication of the lagging strand is discontinuous because of this process of
producing short fragments and joining them to the existing strand. A new fragment
is generated each time the replication fork advances a short distance. This process
continues throughout the entire replication process until the

A

entire DNA has been

replicated.

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29
Q

The new double-stranded DNA re-winds into a ___ as the parental DNA unwinds
exposing more nucleotides to be replicated

A

helix

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30
Q

when the entire chromosome is copied, each double helix consists of one newly synthesized strand of DNA bound to one original parent strand

A

Semiconservative replication

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31
Q

Large, single stranded molecule of nucleotides

A

RNA

32
Q

carries the genetic code

from the DNA to the ribosome

A

mRNA

33
Q

3 Nucleotides =

A

Codon (or 1 amino acid)

34
Q

1 Codon =

A

1 amino acid

35
Q

site of protein

synthesis

A

Ribosome

36
Q

transports and then transfers the amino acid to the developing peptide chain

A

“Transfer RNA” (tRNA)

37
Q

“Triplet code” means that each set of three Nirtrogenous bases codes for an amino acid

A

e.g., UUU, UUC= phenylalaline

CCU, CCC, CCA, CCG = proline

38
Q

Codons are interpreted at the

A

ribosome (for development of polypeptides)

39
Q

the site on the tRNA that bonds with the codon on the mRNA (carries the three bases which complement the codon).

A

Anticodon

Specifies which AA will be carried by the tRNA

40
Q

Assists protein synthesis by serving as a “facilitator” for the mRNA and tRNA functions

A

rRNA

41
Q

Site where codons and anticodons come together

A

rRNA

42
Q

Where amino acids form polypeptides (w/ mRNA)

A

tRNA (anticodon to codon)

43
Q

code on DNA into mRNA

A

Transcription

44
Q

code on mRNA into polypeptide

A

Translation

45
Q

the transfer of the genetic code on DNA gene into a messenger RNA (mRNA) strand by means of DNA-dependent RNA polymerase

A

transcription

46
Q

Transcription steps

A

(1) DNA double-helix unwinds a portion and strands separate thus exposing nucleotides of a gene
(2) RNA polymerase binds to the DNA at the promoter site (beginning of the gene)
(3) Complementary RNA nucleotides are joined together in sequence by the RNA polymerase
(4) Transcription ends when the RNA polymerase reaches the termination region of the gene, and the new single-stranded mRNA is released (the DNA re-winds)

47
Q

Promoter site

A

(right before) beginning of the gene

48
Q

Translation steps

A

(1) mRNA attaches to the ribosome with the “start” codon in place
(2) A tRNA with the complimentary anticodon matches to the codon on the mRNA, thus bringing the first
amino acid into place
(3) As the mRNA codons are matched with complimentary tRNA anticodons, the amino acids are linked together and the tRNA released
(4) Polypeptide chain is released when the reading frame reaches the “stop” codon

49
Q

Multiple ribosomes can attach/read the same mRNA to simultaneously produce two versions of the same polpypeptide/protein

A

Neat

50
Q

are constantly expressed (transcribed and translated into functional products) (60-80% of genes are in this category)

A

Constitutive genes

51
Q

Inducible genes

A

can be “turned on” if the right substrate/enzyme comes along

52
Q

Repressible genes

A

can be “turned off” (meaning they’re normally in the “on” position)

53
Q

related genes that are regulated as a group/series (e.g. genes which code for the enzymes of a single metabolic pathway)

A

Operon

54
Q

codes for a “repressor” protein which can bind to the “operator” region

A

Repressor gene – (located in another portion of the chromosome)

55
Q

Promoter site

A

region of the chromosome to

which the RNA polymerase binds during transcription

56
Q

region of the chromosome which controls (either permits or blocks) access of the RNA polymerase to the structural genes of the operon; site to which the repressor protein binds (or fails to bind)

A

Operator site

57
Q

adjacent genes of the operon which direct the synthesis of proteins with related functions and which are regulated as a unit

A

Genes of the Operon

58
Q

genes are expressed only when certain environmental conditions are present (e.g. genes for enzymes of a biosynthetic pathway are expressed only when the appropriate substrate is present, i.e. presence of substrate causes Operator site to be unblocked.)

A

Inducible operon

59
Q

genes are expressed except when certain environmental conditions are present (e.g. presence of certain metabolic products causes genes for metabolic enzymes to be repressed, thus slowing down metabolism, i.e. presence of metabolic products causes Operator site to be blocked.)

A

Repressible operon

60
Q

Mutation

A

changes (substitutions or deletions) in the sequence of DNA bases, thus changing the genetic code.

61
Q

Mutation types

A

Base Substitution

Frameshift mutatiaon

62
Q

a single base is replaced with another, thus changing the codon. May result in an improper amino acid in the protein

A

Base substitution

63
Q

Silent (base substitution)

A

No change in the protein

64
Q

Missense (base substitution)

A

Different amino acid in the protein; usually not highly significant

65
Q

Nonsense (base substitution)

A

RNA polymerase is stopped from reading the code resulting in an incomplete, nonfunctional protein

66
Q

insertion or deletion of bases may shift the codon reading frame of the mRNA in the ribosome

A

Frameshift mutation

Usually results in missense mutation and significantly different, nonfunctional, or incomplete protein

67
Q

MUtations caused by

A

Spontaneous

or

Chemical mutagens, e.g. nitrous acid, base analogs (do not pair properly), (antibiotics)

or

Radiation - X-ray, gamma rays, ultraviolet light

68
Q

gain, loss, or substitution of entire gene segments or inversions or transpositions of gene sequences to form new combinations of genes.

A

Recombination

a. Results in major change or non-functional cell.
b. Source of genes may be DNA from the same or another microbe (or RNA for certain viruses)

69
Q

small, circular, self-replicating piece of DNA in bacteria

A

Plasmid

Plasmid is separate from the normal chromosomal DNA

70
Q

These genes often code for antibiotic resistance or disease-causing factors

A

plasmid gene

71
Q

integration of the DNA of a temperate bacteriophage (virus) into the bacterial chromosome where it replicates along with the bacterial chromosome

A

Lysogeny

72
Q

(Lysogeny) Viral gene may code for antibiotic resistance or ___

A

disease-causing factors

73
Q

(Lysogeny) Produces new _____ upon separation from the bacterial DNA

A

bacteriophage

74
Q

the transfer of genetic material between donor and recipient cells involving direct cell-to-cell contact

A

Conjugation

A copy of DNA strand or plasmid is
transferred to the recipient cell

75
Q

_____ (hollow tube extending from one bacterium to another) is used to transfer DNA from one cell to another (conjugation)

A

sex pilus (can be plasmid)

76
Q

the direct uptake of DNA segment from one bacterium to another as “naked” DNA in solution (free DNA from one cell is incorporated into the DNA of another; usually follows cell breakdown and release of DNA after bacterial death)

A

Transformation

Results in new characteristics for the recipient cell

77
Q

Transduction

A

the transfer of DNA from donor bacterium to recipient bacterium by using a bacterial virus as the vehicle (host DNA or plasmid is accidentally enclosed in a bacterial virus during exit of the virus from the bacterium)

Bacteriophage is not functional

Micro B2 (7 decks)

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