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Parasitology > Vector Biology And Genetics > Flashcards

Vector Biology And Genetics Flashcards

1
Q

What makes a mosquito a good malaria vector?

A
  • Anthropophagic
  • Endophilic
  • Endophagic
  • High frequency of biting
  • High susceptibility to infection
  • High vector density
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2
Q

What does anthropophagic mean?

A

Preferentially feeds on humans

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3
Q

What does endophilic mean?

A

Rest indoors, associated with the domestic environment

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4
Q

What does endophagic mean?

A

Feeds indoors

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5
Q

What is vectorial capacity?

A

It is a measure of the efficiency of vector-borne disease transmission. It can be summarised as a mathematical equation

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6
Q

What are the factors contributing to vectorial capacity?

A

Mostly genetic

  • Vector density
  • Vector biting frequency
  • Female lifespan
  • Extrinsic incubation cycle
  • Interval between feeding
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7
Q

What is the most important factor which impacts vectorial capacity?

A

The extrinsic incubation period

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8
Q

What is the extrinsic incubation period?

A

It is the latent period of the parasite in the mosquito

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9
Q

What is a species complex?

A

A group of morphologically indistinguishable species which are closely related

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10
Q

What is the species complex in Africa?

A

A. gambiae sensu lato

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11
Q

How many species belong to the A.gambiae species complex?

A

7

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12
Q

Which species belonging to the species complex is the most efficient vector for Plasmodium falciparum spread?

A

A.gambiae sensu stricto

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13
Q

Anopheles species complex properties?

A
  • Related species
  • Morphologically related
  • Vary in behaviour
  • Vary in vector competence
  • Vary in spatial/temporal associations
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14
Q

What do the members of the A.gambiae complex vary in?

A

Behaviour, vector competence, spatial/temporal associations

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15
Q

Population structure of A.gambiae complex?

A

Sympatric population structure- means that the species are present in the same area, they encounter one another

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16
Q

What does sympatric mean?

A

The species exist in the same geographical area

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17
Q

The members of the A.gambiae complex are different species as defined by?

A

The biological species concept

They are reproductively isolated

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18
Q

Mosquitos belong to which order?

A

Diptera

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19
Q

What are polytene chromosomes?

A

These are giant chromosomes which have visible bands

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20
Q

How do polytene chromosomes form?

A

Endoreduplication

There is DNA replication but there is no cell division

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21
Q

What is thought to be the function of polytene chromosomes?

A

Allows larvae to develop much faster

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22
Q

What is endoreduplication?

A

Rounds of DNA replication without cell division

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23
Q

What can occur in polytene chromosomes?

A

Chromosomal inversions

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24
Q

What are chromosomal inversions and how do they form?

A

Form from two cuts occurring in a chromosome

Chromosomal inversions form when a segment of a chromosome becomes reorientated 180 degrees from the normal

25
Q

Pericentric inversions?

A

Include the centromere

26
Q

Paracentric inversions?

A

Do not include the centromere

27
Q

Issues of being an inversion heterozygote?

A

Looping out

Inversion loops form due to incorrect alignment

28
Q

Homologous recombination purpose?

A

To generate genetic diversity

To allow for different combinations to occur

29
Q

What is the issue associated with recombination occurring within chromosomal inversions?

A

Formation of acentric and dicentric chromatids

30
Q

Acentric chromatid?

A

No centromere

31
Q

Dicentric chromatid?

A

Two centromeres

32
Q

The products of recombination within an inverted repeat are?

A

Non-viable

33
Q

As the products of recombination within an inverted repeat are non-viable what occurs?

A

There is cross-over suppression

34
Q

As a result of cross-over suppression?

A

As a result of cross-over suppression the genes in the inversion are genetically linked

35
Q

What is genetic linkage?

A

Linkage is when genes located close together on a chromosome are inherited together

36
Q

The tendency for genes located close together on a chromosome to be inherited together is known as?

A

Genetic linkage

37
Q

What is the overall effect of chromosomal inversion?

A
  • Cross-over suppression

- Tight linkage in the inverted segment as a result

38
Q

What is a co-adapted gene complex?

A

A particular set of alleles at several genes on a chromosome that makes the individuals possessing them very well adapted

39
Q

What threatens to break-up a co-adapted gene complex?

A

Every cycle of meiosis

Genetic recombination

40
Q

What can protect a co-adapted gene complex?

A

If it occurs within an inverted segment where there is cross-over suppression

41
Q

There is very tight linkage of genes in?

A

An inverted chromosomal segment

42
Q

What are the two distinct forms of A.gambiae sensu stricto?

A

Mopti

Savannah

43
Q

What is the main difference between Mopti and Savannah?

A

Differential habitat preference

44
Q

Mopti prefers?

A

Semi-permanent bodies of water e.g. man made larval habitats such as rice fields or flooded areas

45
Q

Savannah prefers?

A

Temporary larval habitats such as puddles and other rain dependent sites

46
Q

What is thought to cause this differential habitat preference?

A

The chromosomal inversions associated with Savannah forms on Chr 2R… believed there is an associated co-adapted gene complex

47
Q

Are the M and S forms reproductively isolated?

A

Not in the lab

In the lab the crosses are viable and fertile

48
Q

Why are no M and S hybrids observed in the wild?

A

Due to pre-mating reproductive isolation mechanisms

49
Q

Are the M and S hybrids separate species?

A

They are not yet separate species but they are at the early stages of speciation

50
Q

Why is it important to know if they are reproductively isolated or not?

A
  • Important for gene drives etc…

- Important for the spread of resistance

51
Q

What allele confers resistance to pyrethroid insecticides?

A

kdr

knockdown resistance allele

52
Q

How has the kdr allele spread?

A

Originated in the S form

Now present in the M form

53
Q

How did the kdr allele enter the M form?

A

Introgression

54
Q

What is linkage?

A

Linkage is the tendency for genes/DNA that are closely associated on a chromosome to be inherited together

55
Q

What are QTLs?

A

There are loci which contain various genes contributing to a particular phenotype

56
Q

How are QTLs mapped?

A

By identifying molecular markers and associating them with certain phenotypes

57
Q

What are two markers which could be used?

A

SNPs

Microsatellites

58
Q

Which marker type is more polymorphic?

A

Microsatellites

59
Q

Once you find a QTL how do you find the causative gene?

A

Home in on the region and see if there are any genes already associated with the particular phenotype
Perform microarrays to see if there is differential expression of certain genes under specific conditions

Parasitology (17 decks)

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