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Applied Genetics > Naming genes, mutations and complementation > Flashcards

Naming genes, mutations and complementation Flashcards

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Biology 101 flashcards
1
Q

how are bacterias named

A

genus with capital
species lower case
all in italics

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2
Q

how are genotype and phenotype linked

A

genotype directly affects the phenotype, if have a mutation may lose or gain a characteristic

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3
Q

what is the genotype

A

genetic material of an individual

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4
Q

what is the phenotype

A

the observable characteristics

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5
Q

what affects phenotype

A

environment

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6
Q

what are the 3 essential features in bacterial gene

A

a promoter
transcribed region
terminator region

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7
Q

what is the promoter for in bacterial gene structure

A

All the sequences in the DNA required for expression and regulation of a gene
These sequences are NOT all included in the mRNA

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8
Q

what is the transcribed region in bacterial gene structure for

A

makes mRNA
Can include more than one ORF (operon)
These sequences ARE included in the mRNA

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9
Q

what terminator sequence in bacterial gene structure for

A

determines where mRNA finishes
Defines end of gene or operon
Often a hair-pin loop

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10
Q

how is mRNA transcribed from prokaryotic gene structure

A

mRNA formed 5’ to 3’

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11
Q

what is included in mRNA structure

A

5’ UTR
translated region
terminator sequence

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12
Q

where is the 5’ UTR

A

before the AUG start codon

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13
Q

where is the translated region

A

Each ORF (open reading frame, must have a RBS) is preceded by a ribosome binding site (RBS)

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14
Q

what is the terminator sequence for

A

Normally a hair-pin loop

Gives mRNA stability

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15
Q

how are genes identified

A

First studies defined genes in terms of observable properties
i.e. by PHENOTYPE

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16
Q

how are phenotypes written

A

as non-italics and often

with a superscript letter to indicate further details

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17
Q

how is something that is resistant to ampicillin antibiotic written

A

Amp^r

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18
Q

how is something that is sensitive to ampicillin antibiotic written

A

Amp^s

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19
Q

what does His ^- mean

A

strain can’t make histidine (would need histidine in media for growth)

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20
Q

what does Lac- mean

A

can’t break down lactose (not necessarily mutant, may have never done it in the first place, so would not be a mutant varies in different strains

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21
Q

how were genes responsible for phenotypes identified

A

Mostly by finding a loss-of-function mutant strain

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22
Q

what is a mutant

A

strain containing a mutation in its genome

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23
Q

how are genotypes written

A

3 letter codes, in lower case and italics. An additional capital letter indicates a specific gene

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24
Q

what indicates gene defined by a mutation, first one found

A

xyz-1

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25
Q

what indicates gene linked to a phenotype, first gene = A

A

xyzA

26
Q

what indicates gene defined as first mutation in gene A

A

xyzA1

27
Q

what is a lacZ gene

A

gene that encodes the enzyme ß-galactosidase

28
Q

what is a lacY gene

A

gene that encodes the enzyme lactose permease

29
Q

what does the number mean lacZ19

A

No other lac mutation will have the number 19 (not just lacZ mutations)

30
Q

what is needed for tryptophan biosynthesis

A

several genes

31
Q

how may a Trp^- phenotype be formed

A

trp mutant may have a mutation in one of a number of genes to give the Trp- phenotype

32
Q

how would trp mutants be named as they are found

A

named trp-1, trp-2 etc

33
Q

what happens to the trp name if analysis shows which gene is mutated

A

a letter can replace the number: trpA or trpB etc.

34
Q

if particular mutations identified what happens to trp name

A

numbers are added: trpA1 or trpB2

35
Q

what is Δ

A

deletion

36
Q

what is ::

A

insertion

37
Q

what is :

A

gene fusion

38
Q

what is xyz’

A

xyz is the gene

3’ end of gene missing

39
Q

what is ‘xyz

A

xyz is the gene

5’ end of gene missing

40
Q

what is xyz^-

A

undefined mutation with gene function lost

41
Q

what is (pXY123)

A

plasmid XY123 inside cell

42
Q

what can cause mutations

A

chemical
physical
biological

43
Q

what can cause chemical mutations

A

Ethyl Methyl Sulphonate (EMS)

44
Q

what can cause physical mutations

A

UV

45
Q

what can cause biological mutations

A

transposons

46
Q

what conditions are ideal in selection

A

Ideally we use Selective conditions

i.e. when either the mutant or ‘wild-type’ will not grow

47
Q

what does the selection method depend on

A

nature of the mutation and its effect on the bacterium

48
Q

what is an auxotrophic mutant

A

require something for growth that the wild-type (prototrophic) bacteria don’t

49
Q

examples of auxotrophic mutants

A
  • wild-type will grow on minimal medium of inorganic salts and glucose
  • an E. coli trp mutant won’t grow on this medium unless tryptophan is also added
50
Q

how are trp mutants found

A

we need to use replica plating colonies on to media +/- tryptophan

51
Q

what happens in selection by replica plating

A

Put all these colonies on and agar plate, hope some have the trp mutant
Want to know which ones are – need to characterize these further
Press agar plate onto velveteen ,get an imprint
Press onto two different plates: one with minimal medium, other with complete that contains trp, (cant make trp if it is mutant for it)
Workout which grow on complete but not minimal

52
Q

what are the replica plating problems

A

In practice using velvet replica plating has a number of drawbacks
It’s easy to smear colonies together
often not all colonies are lifted
transferred colonies can be confused with contaminating bacteria

53
Q

what is a better method than replica plating

A

often cleaner/clearer to use sterilised wooden cocktail sticks to duplicate colonies in a grid on plates

54
Q

which are the easiest mutants to select

A

those which gain a new phenotype as the mutation introduces a marker gene
e.g. resistance to antibiotics (or other biocides)
The only things that grow on a plate containing the biocide
or gaining a new trait
Cells that grow have a visible phenotype

55
Q

what is used for selection by new traits

A

green fluorescent protein
bioluminescence genes (lux)
lacZ - blue/white colony screening

56
Q

what does GFP do

A

Good marker on plasmids –if they’re green, taken up plasmid and expressing GFP marker

57
Q

what causes bacteria to glow (selection by new traits)

A

Plasmid contains many lux genes put into bacteria e.g. e.coli will glow
Use as selection markers

58
Q

what does lacZ show

A

Determine if bacteria has taken up a particular plasmid

59
Q

what is complementation

A

ability of a cloned DNA fragment to ‘complement’ a mutation

i.e. the conversion of the mutant phenotype back to wild type

60
Q

what happens in plasmid complementation - lacZ or lac^- produced

A

beta-galactosidase mutant
produces lacZ or Lac^-
is white colonies

61
Q

what happens in plasmid complementation lacZ^- (placZ^+) or Lac^+

A

beta-galactosidase insert lacZ gene on a plasmid
forms complemented mutant
lacZ^- (placZ^+) or Lac^+
blue colonies

Applied Genetics (20 decks)

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