Polytene Chromosomes in the Salivary Glands of Drosophila melanogasterFull description
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Observing Polytene Polytene Chromosomes in the Salivary Glands of Drosophila virilis Using Wet Mounts and Heat Shock Treatments
evina Chaudhary !"""#$% &Savannah &Savanna h Turon' Turon' &!"()*(('
Section C#
+ab emos Mary ,nn Perron Cloe Petrin
-an "(th. *($/
e0artment of 1iology
University of Otta2a
34T5OUCT3O4 The 0ur0ose of this lab 2as to observe the 0olytene chromosome found in the salivary gland of the fruit 6y larvae7 1y using a control sam0le &in room tem0erature' and com0aring it to a heat shock sam0le &done in an incubator' both the room tem0erature and heat shock chromosomes 2ere observed under a com0ound microsco0e and digital 0hotos 2ere ca0tured7 The lab 2as done in three basic sections. in section one the salivary glands 2ere isolated by dissecting a fruit 6y larva under the dissection microsco0e7 1y 0utting some saline solution on the larva and using t2o needles to remove the head&bringing 2ith it the salivary glands'7 These isolated salivary lands 2ere then 0laced in a 0etri dish 2ith a moist tissue underneath and ke0t aside in room tem0erature7 This 0rocess is done again only 0lacing the ne8t 0etri dish in an incubator at "! degrees Celsius for 9( minutes7 The second 0art of the lab is colouring the chromosomes using aceto:orcein and returning the slide 2ith the dissected larva into the covered 0etri dish for ;ve minutes7 They slides 2ere then removed and observed under the com0ound microsco0e7 3n the last 0art of the lab images of the 0olytene chromosomes 2ere taken using the 3n;nity Ca0ture 0rogram by ad
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A 3b
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B
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3b
Figure 1. &,' The 0olytene chromosomes in the salivary gland of the Drosophila virilis larva at room tem0erature> &1' the 0olytene chromosomes in the salivary gland of the Drosophila virilis larva after a heat shock &"! degrees'7 With 3b being the interbands and 1 are the bands7 Scale bar is */ micrometers in 2idth for both &,' and &1'7 The ;gure above sho2s the cells found in the larva of Drosophila virilis. The chromosomes can b seen inside the nuclei of both the room tem0erature and heat shock sam0le7 3n &,' and &1' the dark banded sections on the chromosomes are called the bands and the more translucent regions are referred to as the interbands7 The heat shock chromosomes are more enlarged and clearly visible under the microsco0e in com0arison to the room tem0erature sam0le7 3SCUSS3O4 $' The 0olytene chromosomes are a good model to sho2 inter0hase stage in the cell. by sho2ing ho2 the chromosomes 2ould be 0ositioned7 3t also hel0s us understand the organi?ation of cells 2hile the undergo cell division. the transcri0tion factors and the overall cycle of cell division7 This is made 0ossible because of the 0olytene chromosomes undergo many series of re0lication containing homologous 0airs and those remain attached &or syna0sed' even 2ithout nuclear division or by being segregated and se0arated7 We also have used heat shock treatments to
study the cell stress res0onse 2hen undergoing more ra0id environment changes &4ordheim.$%)$' 7 @inally scientists have discovered a steroid hormone that undergoes its biochemical 0ath2ay through activation genes7 This 2as found to follo2 a similar activation cycle as the 0uAng of 0olytene chromosomes seen in the lab7 *' The 0olytene chromosomes have lots of 4, and al2ays in inter0hase7 This makes them easier to see inside the nucleus as they are enlarged and the bands and interbands are more clearly distinguished7 Since heat causes the chromosomes to uncoil during 0uAng the chromosomes are less in coiled com0arable to regular cell division &4ordheim. $%)$'7 "' ,s the Drosophila virilis larvae gro2 to2ards the 0u0ation stage they increase in si?e by consuming large amounts of food &similar activity as cater0illars before forming a cocoon to become a butter6y7 1y the Drosophila virilis increasing in its si?e the salivary glands gro2 enormously to hel0 2ith the ingestion and breaking do2n of food. by 0roviding the digestive en?ymes to break do2n the food into its macromolecules7 The salivary glands do not increase in si?e because of ra0id cell division instead the enlarged glands are
chromosomes 2hen the cell 2ill have a high level of 54, 0roduction. 2hich increases the gene activity. due to transcri0tion in the cell7 Transcri0tion can be aected 2hen the environment of the cell is high> this results in the uncoiling of the chromosomes 2hich 2as observed 2hen 2e 0laced the slides under the com0ound microsco0e &,shburner.$%!%' 7 /' The environmental factors can be the eect of hormones that enter or e8it the cell and any genetic mutations &@icB. $%/!'7
5eferences ,shburner. M7. D 1onner. -7 -7 &$%!%'7 The induction of gene activity in roso0hila by heat shock7 Cell. 17&*'. *9$:*/97
@icB. ,7. D Pavan. C7 &$%/!'7 ,utoradiogra0hy of 0olytene chromosomes of 5hynchosciara angelae at dierent stages of larval develo0ment7
4ordheim. ,7. Pardue. M7 +7. +afer. =7 M7. MEller. ,7. Stollar. 17 7. D 5ich. ,7 &$%)$'7 ,ntibodies to left:handed F:4, bind to interband regions of roso0hila 0olytene chromosomes7
