Biology Quiz A Q5: Difference between revisions

Latest revision as of 09:55, 21 March 2025

Biology Quiz A Q5

The final stage of the malaria lifecycle is the re-infection of a mosquito that bites an infected host. This still has some relevance to diagnosis under particular circumstances.

Explanation of correct answer (click "Expand")
Short answer taken from section "Re-infection of the mosquito" (see the section for full details and links). When a mosquito feeds from a malaria infected host, the blood meal will contain parasites of all forms. Importantly these forms include male and female gametocytes. The pH and temperature changes with the mosquito midgut cause the gametocytes to gain full sexual maturity (gametogenesis). The male gametocyte then undergoes 3 cycles of division to generate 8 male sexual forms (gametes). These then 8 gametes then "break out" of the male microgametocytes in a process known as exflagellation, and fuse with the female oocyte (derived from the macrogametocyte). Then following successful fusion move to the next stage of development with the mosquito gut wall. Finally the parasite enter the salivary glands of the mosquito as sporozoites where a new infection can be initiated. If samples of blood undergo delayed spreading then the changes to pH and temperature caused by storage may partly mimic the conditions within the mosquito midgut leading to changes that would only normally be seen in the mosquito. Some may be difficult to recognise but are clearly atypical in appearance, others such as "exflagellation" have very clear appearances. It is important to be able to recognise these forms as they can cause confusion and misdiagnosis: The initial stage involves both the male microgametocytes and female macrogametocytes swelling and becoming more globular (these often clump together). The following stages are quite recognisable for the male gametocte as the male gametes burst from the erythrocytes in the process of exflagellation.

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 |colspan="1" style = "font-size:130%; color:black; background: FFFAFA"|<span style="color:black>'''Biology Quiz A Q5'''</span>
-</br><span style="font-size:90%">On completion of their growth and maturation as trophozoites, a proportion of parasites mature into the sexual (gametocyte) stage that will be concluded within the gut of the mosquito. The stage may form male or female forms which have different size.</span></br></br>
+</br><span style="font-size:90%">The final stage of the malaria lifecycle is the re-infection of a mosquito that bites an infected host. This still has some relevance to diagnosis under particular circumstances.</span></br></br>
 <gallery mode="nolines" widths=200px heights=250px>
-File:Mosquito uptake.jpg.jpg|link={{filepath:Mosquito uptake.jpg.jpg}}
+File:Mosquito uptake.jpg|link={{filepath:Mosquito uptake.jpg.jpg}}
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 {<span style="font-size:90%">Concerning gametocytes which statements are correct? ('''select all true statements''')</br></br>
 |type="[]"}
-- <span style="font-size:90%">The stage arises from schizonts
+- <span style="font-size:90%">Schizonts mediate infection of mosquitos
-+ <span style="font-size:90%">In ''P.falciparum'' they have a "rod" shape
++ <span style="font-size:90%">Sexual replication activates at low pH
-- <span style="font-size:90%">Microgametocytes are the female form
++ <span style="font-size:90%">Microgametocytes undergo exflagellation
-- <span style="font-size:90%">Pigment generally forms a single clump
++ <span style="font-size:90%">Exflagellation may be seen in stored blood
-- <span style="font-size:90%">Red cell size is generally normal
++ <span style="font-size:90%">Macrogametocytes aggregate in stored blood
 </quiz>
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 ! colspan="1" | Explanation of correct answer (click "Expand")
 |-
-|<span style="font-size:90%">''Short answer taken from section "Gametocyte Biology" (see the section for full details and links).</br></br>''A proportion of mature trophozoites give rise to the sexual gametocyte form, contained within ghost red cells (they have metabolised all haemoglobin in order to grow) - The red cell is therefore now simply a membrane that surrounds the parasite without any red colour, but generally retains any cytoplasmic dots typical of the species. Malaria pigment that represents the metabolised haem iron is prominent with different distributions that reflect the species. The appearance of gametocytes does vary according to species and this can aid morphological species identification with red cell appearances typical of the species, and (in the case of ''P.falciparum'' a distinctive straight or curved rod shape.</br></br>
+|<span style="font-size:90%">''Short answer taken from section "Re-infection of the mosquito" (see the section for full details and links).</br></br>''<span style="font-size:90%">When a mosquito feeds from a malaria infected host, the blood meal will contain parasites of all forms. Importantly these forms include male and female gametocytes. The pH and temperature changes with the mosquito midgut cause the gametocytes to gain full sexual maturity (gametogenesis). The male gametocyte then undergoes 3 cycles of division to generate 8 male sexual forms (gametes). These then 8 gametes then "break out" of the male microgametocytes in a process known as exflagellation, and fuse with the female oocyte (derived from the macrogametocyte). Then following successful fusion move to the next stage of development with the mosquito gut wall. Finally the parasite enter the salivary glands of the mosquito as sporozoites where a new infection can be initiated.</br></br>If samples of blood undergo delayed spreading then the changes to pH and temperature caused by storage may partly mimic the conditions within the mosquito midgut leading to changes that would only normally be seen in the mosquito. Some may be difficult to recognise but are clearly atypical in appearance, others such as "exflagellation" have very clear appearances. It is important to be able to recognise these forms as they can cause confusion and misdiagnosis: The initial stage involves both the male microgametocytes and female macrogametocytes swelling and becoming more globular (these often clump together). The following stages are quite recognisable for the male gametocte as the male gametes burst from the erythrocytes in the process of exflagellation.</span></br>
-''' ''P.falciparum'' ''' In this species the gametocytes have a "rod" shape which may be constricted by the remaining red cell membrane to form a curved shape (often described as banana-shaped).</span>
 |}
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+{| class="wikitable" style="width:300px; border-left:solid 4px navy;border-right:solid 4px navy;border-top:solid 4px navy;border-bottom:solid 4px navy; font-size:90%; color:navy; align:center"
-|colspan="1" style = "font-size:90%; color:black|<span style="color:black>[[Biology_Quiz_A_Q5|Go to next question (5 of 5)]]</span>
+|colspan="1" style = "font-size:90%; color:black|<span style="color:black>[[Biology_Quiz_Summary|NEXT PAGE]]</span>

Biology Quiz A Q5: Difference between revisions

From MalariaETC

Latest revision as of 09:55, 21 March 2025