EB21

Question 1

How many deaths are Anopheles mosquitos responsible and how many of them are vectros

Answer 1

655k deaths per year
216 million alaria cases
70/465 are malaria vectors

Question 2

what do anopheles species tend to exist as

Answer 2

species complexes, very closely related groups of species which are morphiological indistinguishable
*adapted to lots of different habitats and ecologies

Question 3

What is An. gambiae

Answer 3

a complex
main vector of malaria in africa
*complex differs in ecology, chromosome inversionsa and genetics.

Question 4

what species are in the An. gambiae complex

Answer 4

1. an. gambiae (split into two forms previously called S adn M now gambiae and coluzii
2. An arabiensis: found in same place as gambaie
3. An. quadriannulatus
4. An ampharicus (prev. An. quadriannaltus)
5. An. bwambae (found in hot springs only)
6. An. merus*
7. An. melas *
   * both found in Bracchis coast regions

Question 5

what do crosses between an. complex species produce

Answer 5

sterile males, fertile females

except gambaie and colluzzi which are fully fertile.

Question 6

how are species in an. complex identified

Answer 6

by chromosomal inversions/banding patterns, via microscopcy of salivary gland

Question 7

what is a chromosomal inversions

Answer 7

chromosome rearragnemetn which occurs when a chromsooem breaks at two pointa nd the segment bounded by break points is reinserted in the reversed orientation
*the two types are paracentric and pericentric

Question 8

what is paracentric inversion

Answer 8

within chromosome arms, does not include the centromere

Question 9

what is a pericentric inversion

Answer 9

across a centromere

Question 10

what is the role of chromosomal inversions in speciation

Answer 10

1. appear to be associated with speciation. (also found in drosophila)
2. reduced recombinatio between different inversion types particularly at break points.
3. if recombination does occur creates unbalanced chromsomes

Question 11

how can formation of unbalanced chromsoomes due to different inversions lead to divergence

Answer 11

if there is an important gene within the inversion that allows adaptation, could cause rapid divergence
** unlikely to cause divergence between forms by itself

Question 12

what other common species have chromsome inversisions

Answer 12

humans and chimps

Question 13

what can we use to reconstruct a phylogeny of Anopheles

Answer 13

fixed and polymorphic inversions.

*several regions fixed within and between species which can be used to reconstruct a phylogeny

Question 14

describe the key X chromosome inversions which help reconstruct the anopheles phylogeny

Answer 14

Xbcd branches to An. arabiensis
Xag branches to An. hambiae and An. merus
X+ branches to An. guadriannalutus, An. bwambae and An. melas

Question 15

describe the patterns of inversion of the left arm of chromosome two 2La

Answer 15

An. arabiensis has 2La as does An. merus
An gambiae has 2L+/a
An. quadriannalutus, An. bwambae and An. melus have the 2L+ form

Question 16

Why did 2La inversion cause confusion

Answer 16

didnt seem to follow pattern expected from X inversion.
Would assume An. merus should be 2L+ not 2La
*assume 2L+ is ancestral

Question 17

Where is the most divergence between An. gambiae and An. arabiensis found, what does this suggest
*what was used to obtain the data

Answer 17

divergence does not vary across autosomes but is higher in X-linked inversions that elsewhere on X or autosomes,
this suggests that this inversion (or a gene within it) is important in the reproductive isolation between the two species
*genomic analysis using SNPs

Question 18

What did an Fst moving window of SNPs across gambiae and arabiensis 2La chromosome compare

Answer 18

An gambiae 2L+/2L+ vs araibiensis 2La/2La

An gambiae 2La/2La vs An arabiensis 2La/2La

Question 19

what were the results of Fst moving window of SNPs comparing 2La of gambiae and arabiensis consistent with

Answer 19

either 2L+ arising before An. gambiae/ararbiensis split. and then being lost in arabiensis or genome wide introgression.
*therefore 2La is now considered the ancestral form

Question 20

what is an introgression

Answer 20

movement of a gene from one species into the gene pool of another by repeated backcrossing of an interspecific hybrid with one of its parent species.

Question 21

what support did subsequent analysis of whole genome of An. gambiae provide for 2La ancestral theory

Answer 21

suggested 2La/2L+ is an ancient inversion polymorphism (segregating in ancestors) that predates the initial diversification of entire complex but is maintained as polymorphic in gambiae and coluzzi
** therefore predating split between arabiensis and gambiae

Question 22

what does fixation of polymorphic inversions between species imply

Answer 22

significant in speciation

Question 23

what could look at polymorphisms maintained within species help wih

Answer 23

working out speciation process.

Question 24

what is the pattern of recombination between inversion types

Answer 24

generally get less recombination betwee inversion types.

with large inversions get recombination in the middle, double crossing over etc.

Question 25

do inversions automatically become a barrier to gene flow

Answer 25

no some inversions remain polymorphic in a species.

Question 26

how are polymorphic inversions usually maintained in populations

Answer 26

at HWE

Question 27

how can inversion frequencies be related to habitat

Answer 27

sometimes there is a gradient of inversion frequencies associated with adaptation to different habitats

Question 28

what does degree of divergence and linkage disequilibrium (non-random association of alleles at different loci) depend on

Answer 28

genes within inversions - must also be selection

Question 29

what has the 2La inversion in anopheles been associated with

Answer 29

tolerance to aridity

Question 30

what inversions occur on chromosome 2

Answer 30

numerous inversions can be seen on chromosome 2 | however 2La is the largest

Question 31

what can frequency of 2La inversion be correlated with

Answer 31

positive correlation with more arid habitats. | *plotting according to habitat type; wet to dry transect clear increase in 2La frequency.

Question 32

what other inversions show an increase with aridity

Answer 32

2Lbc - however not as pronounced as 2La

Question 33

what was found to be a pattern in several inversions

Answer 33

that certain inversions always occured together in individuals and that certain combos never ocurred

Question 34

what happens if you group individuals based on corresponding inversions

Answer 34

found three formed | named Bamako, Savanna and Mopti.

Question 35

how were morpti, bamako and savanna further distinguished

Answer 35

ribosomal DNA marker found that distinguished Mopti from Bamako and Savanna led to formation of M and S molecular forms M: roughly corresponds to Mopti, savanna, forect and bissau S: roughly corresponds to Bamako, forest and savanna.

Question 36

how are S and M form distributed

Answer 36

Only S is found in east africa | both forms occur sympatrically in west and central africa. but skewed depending on habitat and dryness.

Question 37

what did the 2010 analysis of the two forms show?

Answer 37

high genome wide divergence, particularly at genes associated with odorant receptors (associated with mae choice) and resistance to insecticides (RdI gene; resistant to dieldrin)

Question 38

what did the 2012 analysis of the 2 forms of wild caught mosqutios show

Answer 38

again show high divergence in certain parts of the genome *places where two forms found together different parts of the genome has different levels of divergence. (some very high/overs less) - but gene flow did occur

Question 39

what was the 2012 analysis of the two forms in the wild

Answer 39

genome scan of divergence along chromosome arms between the two sympatric population samples of M and S at different locations,

Question 40

what was the 2013 analysis using SNPs of M and S

Answer 40

time series data collected for sympatric populations from a town. (selinkenyi) *looked at diagnostic SNPs in X, 2L and 3L chromosome arms

Question 41

what did the 2013 time series of M and S SNPS show

Answer 41

1. M and S seem to be mostly homozygous and seperate for the firsty 13 years of the study 2. in 2006 suddenly get large no. of heterozygotes (M/S) continuing for several years afterwards in X, 2L and 3L 3. after 4 years heterozygotes are much less common in X and 3L but still common in 2L. * found large section of 2L moved from S to M

Question 42

what was pattern in time series trend over the years found to be due to

Answer 42

section contained insecticide resistance gene selection pressure was spo strong that the small amount of natural hybridisation enabled spread. *assortative mating between M and S.

Question 43

are M and S are species?

Answer 43

usually look at hybridisation between the but quickly go back to segregating out and becomign quite divergent again across most of the genome

Question 44

what are the premating barriers to prevent hybridisation of M and S

Answer 44

1. male mosquitos form swarms; however mixed swarms are rare as tend to occur in different places. *seem to occur less frequently than would be statistically expected. 2. different habitat preference M prefers standing water (man-made irrigation areas), S more natural puddles 3. Flight tone variation; may be related to mate choice (sound different to females) **mixed swarms do occur with little or no mating discrimination in these.

Question 45

what are the post mating barriers of M and S

Answer 45

none hybridise freely in the lab to form chimeric strains *hybrids can be found in the wild (1-97% depending on location)

Question 46

in 2013 what was decided about M and S

Answer 46

they were two species M = colluzii S = gambiae ** however the debtate continues