Vector Biology And Genetics

Question 1

What makes a mosquito a good malaria vector?

Answer 1

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

Question 2

What does anthropophagic mean?

Answer 2

Preferentially feeds on humans

Question 3

What does endophilic mean?

Answer 3

Rest indoors, associated with the domestic environment

Question 4

What does endophagic mean?

Answer 4

Feeds indoors

Question 5

What is vectorial capacity?

Answer 5

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

Question 6

What are the factors contributing to vectorial capacity?

Answer 6

Mostly genetic

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

Question 7

What is the most important factor which impacts vectorial capacity?

Answer 7

The extrinsic incubation period

Question 8

What is the extrinsic incubation period?

Answer 8

It is the latent period of the parasite in the mosquito

Question 9

What is a species complex?

Answer 9

A group of morphologically indistinguishable species which are closely related

Question 10

What is the species complex in Africa?

Answer 10

A. gambiae sensu lato

Question 11

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

Answer 11

7

Question 12

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

Answer 12

A.gambiae sensu stricto

Question 13

Anopheles species complex properties?

Answer 13

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

Question 14

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

Answer 14

Behaviour, vector competence, spatial/temporal associations

Question 15

Population structure of A.gambiae complex?

Answer 15

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

Question 16

What does sympatric mean?

Answer 16

The species exist in the same geographical area

Question 17

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

Answer 17

The biological species concept

They are reproductively isolated

Question 18

Mosquitos belong to which order?

Answer 18

Diptera

Question 19

What are polytene chromosomes?

Answer 19

These are giant chromosomes which have visible bands

Question 20

How do polytene chromosomes form?

Answer 20

Endoreduplication

There is DNA replication but there is no cell division

Question 21

What is thought to be the function of polytene chromosomes?

Answer 21

Allows larvae to develop much faster

Question 22

What is endoreduplication?

Answer 22

Rounds of DNA replication without cell division

Question 23

What can occur in polytene chromosomes?

Answer 23

Chromosomal inversions

Question 24

What are chromosomal inversions and how do they form?

Answer 24

Form from two cuts occurring in a chromosome

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

Question 25

Pericentric inversions?

Answer 25

Include the centromere

Question 26

Paracentric inversions?

Answer 26

Do not include the centromere

Question 27

Issues of being an inversion heterozygote?

Answer 27

Looping out | Inversion loops form due to incorrect alignment

Question 28

Homologous recombination purpose?

Answer 28

To generate genetic diversity | To allow for different combinations to occur

Question 29

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

Answer 29

Formation of acentric and dicentric chromatids

Question 30

Acentric chromatid?

Answer 30

No centromere

Question 31

Dicentric chromatid?

Answer 31

Two centromeres

Question 32

The products of recombination within an inverted repeat are?

Answer 32

Non-viable

Question 33

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

Answer 33

There is cross-over suppression

Question 34

As a result of cross-over suppression?

Answer 34

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

Question 35

What is genetic linkage?

Answer 35

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

Question 36

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

Answer 36

Genetic linkage

Question 37

What is the overall effect of chromosomal inversion?

Answer 37

- Cross-over suppression | - Tight linkage in the inverted segment as a result

Question 38

What is a co-adapted gene complex?

Answer 38

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

Question 39

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

Answer 39

Every cycle of meiosis | Genetic recombination

Question 40

What can protect a co-adapted gene complex?

Answer 40

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

Question 41

There is very tight linkage of genes in?

Answer 41

An inverted chromosomal segment

Question 42

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

Answer 42

Mopti | Savannah

Question 43

What is the main difference between Mopti and Savannah?

Answer 43

Differential habitat preference

Question 44

Mopti prefers?

Answer 44

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

Question 45

Savannah prefers?

Answer 45

Temporary larval habitats such as puddles and other rain dependent sites

Question 46

What is thought to cause this differential habitat preference?

Answer 46

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

Question 47

Are the M and S forms reproductively isolated?

Answer 47

Not in the lab | In the lab the crosses are viable and fertile

Question 48

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

Answer 48

Due to pre-mating reproductive isolation mechanisms

Question 49

Are the M and S hybrids separate species?

Answer 49

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

Question 50

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

Answer 50

- Important for gene drives etc... | - Important for the spread of resistance

Question 51

What allele confers resistance to pyrethroid insecticides?

Answer 51

kdr | knockdown resistance allele

Question 52

How has the kdr allele spread?

Answer 52

Originated in the S form | Now present in the M form

Question 53

How did the kdr allele enter the M form?

Answer 53

Introgression

Question 54

What is linkage?

Answer 54

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

Question 55

What are QTLs?

Answer 55

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

Question 56

How are QTLs mapped?

Answer 56

By identifying molecular markers and associating them with certain phenotypes

Question 57

What are two markers which could be used?

Answer 57

SNPs | Microsatellites

Question 58

Which marker type is more polymorphic?

Answer 58

Microsatellites

Question 59

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

Answer 59

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