Guide to STPM Practicals For Third Term
Construction of a Dichotomous Key Using Local Specimens This experiment enables students to: 1. Identify the external features (morphology) (morphology) of an organism to be grouped into a phylum phylum or a class 2. Increase their knowledge knowledge in the eld of taxonomy 3. To use a dichotomous dichotomous key to identify unknown plants or animals. Organisms such as Amoeba sp sp.. (slide), Hydra sp. (slide), ant, snail (garden snail), shrimp, Marchantia Mar chantia sp. (moss), Dryopteris (moss), Dryopteris sp. (with sori on the undersides of the fronds) and grass were examined under the microscope or using a magnifying glass (× 10). The opposing features, which clearly differentiate the organisms from one another, were noted down. A dichotomous key for this group of organisms was then constructed up to the category of phylum and class. Characteristics of organisms noted: Organism
Characteristics
Grass
Green, containing chlorophyll; does not produce spores; has owe owers, rs, roots, stems and leaves
sp.. Dryopteris sp
Containing chlorophyll; produces spores; fronds sub-divided into pinnae and pinnules bearing sori on undersides undersides
Marchantia sp sp..
Containing chlorophyll; produces spores; thalloid body with rhizoids; has gemma cups, antheridiophores and archegoniophores as reproductive structures
Amoeba sp sp..
Organism without chlorophyll; unicellular. unicellular.
Hydra sp sp..
Multicellular; soft cylindrical body without exoskeleton; body wall comprises of two layers of cells − ectoderm and endoderm; has tentacles, a gut cavity and a mouth
Snaail Sn
Multicellular; wit ith h exoskeleton; ha has so soft mu musc scu ular fo foot an and calcareous sh shell
Ant
Invertebrate with jointed legs; body divided into head, thorax and abdomen; has three pairs of legs; wingless
Shri Sh rimp mp
Inver Inv erte teb bra rate te;; bod body y div divid ided ed in into to ce cep pha halo loth tho ora rax x an and abd abdom omen en;; has has tw two o pai pairs rs of antennae and ve pairs of jointed legs
From the above observations, it can be inferred that, Mar Marchantia chantia sp. is able to live successfully in highlands and damp areas due to its special rhizoids. The structural differences between Mar between Marchantia chantia and Dryopteris and Dryopteris are that Mar that Marchantia chantia has a thalloid body and gemmae cups whereas Dryopteris has roots, stems, and leaves with the presence of sori on the underside of its fronds. Ant and shrimp share the same phylum, Arthropoda Arthropoda as both have segmented body with wit h exoskeleton and jointed legs. The structural differences between them can be seen in the table below: Ant
Shrimp
(a) Segmented body with exoskeleton which is Segmented body with exoskeleton which is divided into head, thorax and abdomen divided into cephalothorax and abdomen (b) 3 pairs of jointed legs
5 pairs of jointed legs
(c) A pair of antennae
2 pairs of antennae
(d) Tr Tracheal system for respiration
Gills for respiration © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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A simple spider key, showing contrasting characteristics ca n b e u sed to differentiate the organisms for the purpose of constructing a dichotomous key. Organisms Organisms with chlorophyll
Organisms without chlorophyll Amoeba, Hydra, ant, snail, shrimp
Marchantia, Dryopteris, grass non-flowering/producing spores
flowering/not producing spores
unicellular
multicellular Hydra, ant, snail, shrimp
Marchantia, Dryopteria Without archegonia and antheridiophores
Dryopteris
Grass with archegonia and antheridiophores
Amoeba
without tentacles
Ant, snail, shrimp
Hydra
with leg
Marchantia
without leg
Ant, shrimp
six legs
Snail
ten legs
Ant
Dichotomous key A1 With chlorophyll A2 Without chlorophyll B1 Does not produce spores but has owers, roots, stems and leaves B2 Produces spores C1 Fronds sub-divided into pinnae and pinnules bearing sori on undersides C2 Thalloid body, has gemma cups, antheridiophores and archegoniophores as reproductive structures D1 Unicellular D2 Multicellular E1 Soft cylindrical body without exoskeleton. Body wall comprises of ectoderm and endoderm. Tentacles, gut cavity and mouth present E2 With exoskeleton F1 Invertebrate with soft muscular foot and calcareous shell F2 Invertebrate with jointed legs G1 Invertebrate; body divided into head, thorax and abdomen. Has three pairs of legs; wingless G2 Invertebrate; body divided into cephalothorax and abdomen. Has two pairs of antennae and ve pairs of legs
2
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with tentacles
Shrimp
refer to B refer to D Phylum Angiospermae (Grass) refer to C Phylum Filicinophyta ( Dryopteris) Phylum Bryophyta ( Marchantia) Phylum Protoctista ( Amoeba) refer to E
Phylum Cnidaria ( Hydra) refer to F Class Mollusca (Snail) refer to G Class Insecta (Ant)
Class Crustacea (Shrimp)
Guide to STPM Practicals
Preservation of Plant and Insect Specimens This experiment enables students to: 1. Learn the skill of preservation of plants and insects prior to related experiments 2. Understand better the eld of taxonomy 3. Identify the morphological features of plants and insects 4. Determine the phylum, class and order of the preserved plants and insects Below are some of the plants and insects that can be preserved by dry or wet preservation techniques using FAA solution or 70% ethanol as preservative. Both these techniques can cause the colour of the specimens to fade and therefore their original colour should be noted before preserving them. Insects can be killed by squeezing their thorax or abdomen gently to block their air passages. Both the preservation techniques enable the plants and i nsects to be preserved for a long time. Gemma cups
Male “umbrellas”
Female “umbrellas”
Marchantia sp . is a liverwort commonly found in owerpots in green houses, on moist bricks in gardens and on badly drained soils. On its thalloid body are small gemma cups with small oval pieces of tissue, which can be spread by raindrops and become new plants. This dioecious bryophyte can easily be identifed by its male and female “umbrellas” which carry the male and female receptacles. Marchantia belongs to the division, Bryophyta and class, Hepaticae. Dryopteris sp . which belongs to the division, Filicinophyta and class, Filicinae is a common fern found growing in dry open area. It is a hardy plant which reproduces rapidly and asexually by means of spores found in the sporangia that grow in clusters called sori on the underside of its fronds. The fern is also capable of reproducing sexually.
or
Both the housey and the dragony or grasshopper (or locust) belongs to the phylum, Arthropoda which has the characteristics of segmented body, jointed legs in pairs, chitinous exoskeleton and open circulation. Both the animals belong to the class Insecta, which can be characterized by their bodies being divided into 3 distinct regions, that is, the head, thorax and abdomen. The head bears a pair of antennae, the thorax bears 3 pairs of jointed legs and the body is well supplied with respiratory tubes or trachea. The housey belongs to the order Diptera, whereas the grasshopper/ locust belongs to the order Orthoptera. Dragonies, however belong to the order Odonata. © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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Guide to STPM Practicals
Collection of Insects This experiment enables students to: 1. Be aware of the diversity of insects in Malaysia 2. Learn the insects’ habitats, feeding and sexual behaviour, and their economic values 3. Strengthen their concept and understanding of classication and nomenclature 4. Inculcate their love towards all living things and nature Capturing of insects and preserving them 1. Insects can be captured by: (a) Sweeping small bushes with a net (b) Catching ying insects like butteries directly with a net (c) Using a light trap to catch nocturnal insects
2. The captured insects are then placed into the killing jar containing cotton wool soaked in concentrated ethanol. After the insects have been fully paralyzed, they are pinned on a piece of polystyrene to x the position. 3. With suitable dissecting tools, the abdomen of the insect is slit open and the internal organs were removed. A wad of formalin-soaked cotton wool is then inserted into the abdominal cavity (see diagrams below). 4. Formalin is also injected into parts which are too small to be cut. The slit is then sealed.
The abdomen of the insect is slit open and the internal organs are removed
A wad of formalin-soaked cotton wool is inserted into the abdominal cavity
5. The preserved insects are then clearly displayed and pinned onto a polystyrene. Each insect is labeled as follows: Local name: Order: Location: Habitat: Date of collection: Collector’s name: ( A total of 10 different species from ten different orders of insects are to be collected ) 6. A suggested list of insects is given below. (a) Local name: Longhorn beetle Scientic name: Batocera davidis Order: Coleoptera (b) Local name: Brown spruce longhorn beetle Scientic name: Tetropium fuscum Order: Coleoptera 4
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(c) Local name: Titanic stag beetle Scientic name: Dorcus titanic Order: Coleoptera (d) Local name: Elephant beetle Scientic name: Xylotrupes ulysses Order: Coleoptera (e) Local name: Click Beetle Scientic name: Limonius canus Order: Coleoptera (f) Local name: Sloe bug Scientic name: Dolycoris baccarum Order: Hemiptera (g) Local name: Carpenter bee Scientic name: Xylocopa violacea Order: Hymenoptera (h) Local name: Carpenter bee Scientic name: Xylocopa aruana Order: Hymenoptera (i) Local name: Honey bee Scientic name: Vespa afnis Order: Hymenoptera (j) Local name: Peacock pansy Scientic name: Junonia almana Order: Lepidoptera (k) Local name: Striped albatross Scientic name: Appias libythea olferna Order: Lepidoptera (l) Local name: Paper kite Scientic name: Idea leuconoe Order: Lepidoptera (m) Local name: Great orange-tip buttery Scientic name: Hebomoia glaucippe Order: Lepidoptera (n) Local name: Pepatung merah Scientic name: Nannophya pygmaea Order: Odonata (o) Local name: Ruby meadowhawk dragony Scientic name: Crocothemis servilia Order: Odonata (p) Local name: Red grasshawk dragony Scientic name: Neurothemis uctuans Order: Odonata (q) Local name: Common skimmer Scientic name: Neurothemis intermedia Order: Odonata (r) Local name: Blue dragony Scientic name: Trithemis festiva Order: Odonata © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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(s) Local name: Common eld grasshopper Scientic name: Chorthippus brunneus Order: Orthoptera (t) Local name: Short horned grasshopper Scientic name: Chorthippus parallelus Order: Orthoptera (u) Local name: Grasshopper Scientic name: Valanga nigricornis Order: Orthoptera (v) Local name: Katydid Scientic name: Pterophylla camellifolia Order: Orthoptera (w) Local name: Sawy Scientic name: Arge humeralis Order: Hymenoptera (x) Local name: Stick insect Scientic name: Phasma reinwarditi Order: Phasmida (y) Local name: Cicada Scientic name: Cicadetta montana Order: Homoptera 7. Some interesting insects that are found around your neighbourhood.
6
Local name: The wood nymph Order: Lepidoptera
Local name: Stick insect Order: Phasmida
Local name: Stag beetle Order: Coleoptera
Local name: Red dragonfly Order: Odonata
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Guide to STPM Practicals
Collection of Plants
This experiment enables students to: 1. Be aware of the plant diversity in Malaysia 2. Inculcate the love for plants and nature 3. Strengthen their understanding of classication of plants and nomenclature 4. Learn the economic values of Malaysian plants Collection and preservation process 1. Plant specimen to be collected should not be too young or too old and cut to the size to t a tabloid newspaper. Only the leaf and stem (owers if any) should be collected.
2. Specimens are pressed immediately after collection and put into the oven at 105 °C to rid them of water (see pictures below).
The selected specimen immediately after collection.
is
pressed
The specimen is then put into the oven at 105 °C to dry it.
Dried stems and leaves are then mounted.
3. The dried specimen is then mounted onto drawing papers of size 6 in. × 10 in. or 13 in. × 8 in. 4. Each plant specimen is fully labelled as follows: Local name: Family: Location: Habitat: Date of collection: Collector’s name: ( A total of 10 different species from ten different families of plants are to be collected ) 5. A suggested list of plants that can be collected: (a) Local name: Asoka Scientic name: Saraca indica Family: Fabaceae (b) Local name: Sial menaun Scientic name: Pternandra coerulescens Family: Melastomataceae (c) Local name: Pandan jepun Scientic name: Pandanus amaryllifolius Family: Pandanaceae (d) Local name: Ubi kayu Scientic name: Manihot utilissima Family: Euphorbiaceae © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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(e) Local name: Angsana Scientic name: Pterocarpus indicus Family: Papilionaceae (f) Local name: Tecoma Scientic name: Tabeayaia pentaphylla Family: Bignoniaceae (g) Local name: Beringin/ Malayan Banyan Scientic name: Ficus microcarpa (van nitida) Family: Moraceae (h) Local name: Pulai Scientic name: Alstonia scholaris Family: Apocynaceae (i) Local name: Kelat paya Scientic name: Eugena papilosa Family: Myrtaceae (j) Local name: Gapis Scientic name: Saraca thaipingensis Family: Caesalpiniaceae (k) Local name: Saga Scientic name: Adenanthera pavonina Family: Fabaceae (l) Local name: Melinjau Scientic name: Gnetum gnemon Family: Gnetaceae (m) Local name: Duku Scientic name: Lansium domesticum Family: Meliaceae (n) Local name: Durian Scientic name: Durio zibethinus Family: Bombacaceae (o) Local name: Gelam Scientic name: Melaleuca leucadendron Family: Myrtaceae (p) Local name: Gaharu Scientic name: Aquilaria malaccensis Family: Thymelaeaceae (q) Local name: Gajus Scientic name: Anacardium occidentale Family: Anacardiaceae (r) Local name: Mango Scientic name: Mangifera indica Family: Anacardiaceae (s) Local name: Cempedak Scientic name: Artocarpus champeden Family: Moraceae 8
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(t) Local name: Berangan Scientic name: Castanopsis inermis Family: Fagaceae (u) Local name: Penaga lilin Scientic name: Mesua ferrea Family: Clusiaceae (v) Local name: Nangka Scientic name: Artocarpus heterophyllus Family: Moraceae (w) Local name: Ixora Scientic name: Ixora javanica Family: Rubiaceae (x) Local name: Kayu manis hutan Scientic name: Cinnamomum iners Family: Lauraceae (y) Local name: Badam Scientic name: Prunus spp. Family: Rosaceae 6. Some interesting plants that can be collected.
Lidah buaya – Aloe vera
Cekur – Kaempferia galanga
Hempedu bumi – Andrographis paniculata
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Guide to STPM Practicals
Ecological Study of a Terrestrial Ecosystem This experiment enables students to: 1. Learn the basic principles of ecology through hands-on experience 2. Understand the biotic and abiotic elements of ecosystems 3. Understand the dynamic relationship of elements and energy ow in an ecosystem 4. Learn the simple instrumentations (improvised or otherwise) in ecological studies 5. Learn the methods of collecting and analysing ecological data 6. Write a systematic ecological study report 7. Inculcate the love for nature 8. Inculcate good moral values, independence and self-condence Some of the useful ecological tools that you may use in the course of your study.
10
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Determination Of Plant Population Using A Quadrat Sampling Technique 1. Students may carry out this study in groups of 4 or 5 but individual report is required. 2. Each group should determine the area to be studied, the objectives, rough working plan, and the techniques to be carried out. 3. The plant distribution of a terrestrial habitat can be determined by using quadrats. 4. The results can be tabulated (see tables and examples below) and calculations should be done using the formulae given below. Quadrat sampling of plants in an open area
Quadrat size: 0.5 m 2 (Random sampling)
An open area (Notice the laterite soil)
Formula:
(a) Species × frequency =
no of quandrat containing the species x
(b) Relative species × frequency =
(c) Species × density =
Species x frequency Total frequency of all species
× 100
Total number of the species x (Total number of quadrat x area of each quadrat)
(d) Relative species × density =
(e) Species × coverage =
× 100
total number of quandrats
Species x density Total density of all species
Total area of coverage of species x Total number of quandrat
(f) Relative species × coverage =
× 100
× 100
Species x coverage Total coverage of all species
× 100
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Table 1: Presence of plant species
Quadrat
Total number Species of quadrat frequency containing (%) 10 species x
Plant species ( x) 1
2
3
4
Acantha sp.
5
6
�
Ischaemum sp.
�
�
�
�
�
�
7
8
9
�
�
�
4
40
12.12
�
�
�
9
90
27.27
1
10
3.03
�
6
60
18.18
�
4
40
12.12
�
5
50
15.15
�
2
20
6.67
�
2
20
6.67
33
330
Imperata cylindrica
�
Lycopodium sp.
�
�
�
�
�
Melastoma malabathricum
�
�
�
Eleucine sp.
�
�
�
Polygala sp.
�
Bryophyllum sp.
Relative species frequency (%)
�
�
Total Table 2: Number of plant species Plant species
1
Acantha sp. Ischaemum sp.
2
3
15 55 50
Imperata cylindrica Lycopodium sp.
Total Species number of density (/m ) 10 species x
Quadrat
4
5
6
7
8
9
5
56 49 13 13 60 32 28 26 30
2
11 30 10 20
Melastoma malabathricum Eleucine sp. Polygala sp.
3
8
5 70
7 7 23 98 55 20 10 25
5
Bryophyllum sp.
14
4
6
Total
Relative species density (%)
131 301
52.4 120.4
15.23 35.00
11
4.4
1.28
85
34.0
9.88
42
16.8
4.88
253 27
101.2 10.8
29.42 3.14
10
4.0
1.16
860
344.0
10
Total area Species of coverage coverage of species x (%) (cm2) 2100 21000 5720 57200
Table 3: Area of coverage Quadrat (area covered by each spp, cm2 ) Plant species Acantha sp. Ischaemum sp. Imperata cylindrica Lycopodium sp. Melastoma malabathricum Eleucine sp. Polygala sp.
1
150
2
3
1000 1000
4
5
50
1000 1200
6
7
8
9
640
900 560
100 520
100 600
220 600
200
400
30
80
90
70
980
2200 1500
50
Bryophyllum sp.
70
80
400 800 120
Relative species coverage (%) 12.61 34.35
220
2200
1.32
280
1590
15900
9.55
460
690
6900
4.14
200
5280 850 200 16650
52800 8500 2000 166500
31.71 5.11 1.20
Total
The plant species that shows the highest species frequency / species density / species coverage is the most dominant species in the habitat. 12
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Soil Analysis 1. Soil sampling technique Metal cylinders or tin cans (improvised tools) are pressed or hammered into the soil to collect the soil sample. The soil sample is taken back to the school science laboratory in the cylinder for further analysis (see picture below).
Soil sample in metal cylinder
Laterite soil from open area
Soil colour hints its content
2. Determination of soil texture Students may use a soil sieve or measuring cylinder to determine the percentage of each soil component as shown below.
Sieves of different mesh sizes are used to determine the amount of clay, silt and sand in the soil sample. A measuring cylinder (on the right) can also be used for the same purpose. Calculation of the percentage of components of soil sample Formula Percentage of soil component
height of soil component =
total height of soil sample
× 100% (using measuring cylinder method)
Working: Percentage of clay 5.55 = × 100% = 59.67 % 9.30
Percentage of silt 1.87 = × 100% = 20.11 % 9.30 Percentage of sand 1.88 = × 100% = 20.22 % 9.30 Texture of soil
Height (cm)
% of soil component
clay
5.55
59.67
silt
1.87
20.11
sand
1.88
20.22
Total
9.30
100.00 © Oxford Fajar Sdn. Bhd. (008974-T) 2013
13
Y L A C T N E C R E P
P E R C E N T S I L T
PERCENT SAND
3. Determine of soil sample pH A sample of soil is added to a test tube contain a spatula of barium sulphate which helps to 3 precipitate the clay particles in a soil sample suspension. The test tube is then lled with 4 water and shaken after adding 5-6 drops of Universal Indicator. A clear coloured liquid is formed above the soil which is noted and the pH recorded as shown in Table 4. The pH of the soil is then correlated to the plant species that is most suitable to live in this pH condition. Table 4: Soil sample
Colour
pH
1
red
4
2
red
4
3
yellow
6
4
red
5
5
yellow
6
Average pH
5
The colour of the liquid above the soil sample is compared with the Universal Indicator Chart to determine the pH of the soil.
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Use of the χ2 Test in Monohybrid and Dihybrid Genetic Crosses This experiment enables students to use the χ 2 test to determine whether a set of experimental data obeys Mendel’s rst and second law. The monohybrid ratio 3:1 and dihybrid ratio 9:3:3:1 are hypothetical estimations based on dominant and recessive genes, segregation, independent assortment and random fertilisation which may be inuenced by chance events and will be subjected to normal deviation. To assess a genetic hypothesis, a χ2 test was used which can change the deviation from the expected value/ ratio to the probability that chance alone could be responsible for the deviation. This test takes into account the sample size and the number of parameters (degree of freedom). For most problems in genetics, the degree of freedom (df) is one less the number of classes of phenotypes (n). For example, in a monohybrid cross, where only one trait, that is, the colour of maize seed (purple which is dominant over yellow) is considered (n = 2), then the df is n – 1 = 2 – 1 = 1. In a dihybrid cross, where two traits, that is, the colour of maize seed (purple and yellow) and the conditions of maize seed (smooth which is dominant over wrinkled) are considered ( n = 4), then the df is n – 1 = 4 – 1 = 3. In this experiment, the phenotypes of the maize seeds are counted from the ears of corn given as below and the results tabulated. 1. Ears of corns from monohybrid crosses (a) The phenotypes: purple and yellow seeds (b) The phenotypes: smooth and wrinkled seeds
Purple seed
Yellow seed
2. Ears of corns from dihybrid cross The phenotypes: purple / yellow and smooth / wrinkled seeds.
Purple wrinkle seed Purple smooth seed Yellow wrinkle seed Yellow smooth seed
From the results, the values of χ2 are calculated and compared with the values given in the table below.
χ2 =
∑(o – e)
2
(e)
o = observed value, that is, the actual number of seeds of a particular phenotype e = expected value, that is, the number of seeds of a particular phenotype calculated from the monohybrid and dihybrid ratios © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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χ2 table df\p
.99
.98
.95
.90
.80
.70
.50
.30
.20
.10
.05
.02
.01
1
.00016 .00063
.0039
.016
.064
.148
.455
1.074
1.642
2.706
3.841
5.412
6.635
2
.0201
.0404
.103
.211
.446
.713
1.386
2.408
3.219
4.605
5.991
7.824
9.210
3
.115
.185
.352
.584
1.005
1.424
2.366
3.665
4.642
6.251
7.815
9.837
11.341
4
.297
.429
.711
1.064
1.649
2.195
3.357
4.878
5.989
7.779
9.488
11.668 13.277
p − Probability df − Degree of freedom Monohybrid cross (Mendel’s rst law) Phenotype
Expected Observation Expected ratio (o) number of count (e)
Divergence Divergence2 Divergence2 / (o – e) (o – e)2 Expected no. of count (o – e)2 /(e)
Yellow
1
79
72.75
6.25
39.0625
0.537
Purple
3
212
218.25
6.25
39.0625
0.179
291
Total
0.716
χ2 = 0.716
Conclusion: The calculated χ2 value (0.716) is found to be lower than the value (3.841) given in the χ2 table (P0.05, df = 1). Therefore the deviation is not signicant and the result obeys Mendel’s rst law. Dihybrid cross (Mendel’s second law) Phenotype
Expected Observation ratio (o)
Expected Divergence Divergence2 Divergence2 / number of (o – e) (o – e)2 Expected no. of count count (e) (o – e)2/(e)
Purple smooth
9
669
675
–6
36
0.053
Yellow smooth
3
232
225
7
49
0.218
Purple wrinkled
3
231
225
6
36
0.160
Yellow wrinkled
1
68
75
–7
49
0.653
Total
1200
1.084
χ2 = 1.084 Conclusion: The calculated χ2 value (1.084) is found to be lower than the value (7.815) given in the χ2 table (P0.05, df = 3). Therefore the deviation is not signicant, the dihybrid ratio of 9:3:3:1 is accepted and the result obeys Mendel’s second law.
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Guide to STPM Practicals
Extraction of Plant DNA This experiment enables students to: (a) To indicate the presence of DNA in living cells. (b) To describe the physical characteristics of DNA. Deoxyribonucleic acid (DNA) is a nucleic acid that contains the entire genetic information of an organism is found in its nucleus. DNA is formed from nucleotide subunits namely thymine (T), adenine (A), guanine (G) and cytosine (C). In a cell, DNA exists in the form of double-stranded helix molecule of polynucleotide where there is base-pairing between A and T, and G and C. These two strands run in opposite directions to each other and are anti-parallel. A segment of DNA that carries the genetic information is called a gene. In this experiment, students will use nely-crushed onion succulent leaves and a DNA Extraction Kit (see below) to help them to extract DNA from the onion leaves following the instructions given. The onion leaves must rst be homogenized to break down the cell wall as to release the DNA from the plant cell. The isopropanol is used to precipitate the DNA extracted. In a proper forensic investigation, DNA in a solution can be visualized using the electrophoresis method.
At the end of the experiment, a whitish, sticky and slimy DNA is extracted and precipitated at the tip of a pooling stick.
A whitish, sticky and slimy DNA is extracted and preciptated at the end of a pooling stick. © Oxford Fajar Sdn. Bhd. (008974-T) 2013
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