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Sindh Botany 2022 — Solved Past Paper with Answers
All 15 MCQs from Sindh Botany 2022, solved with the correct answer highlighted and a full explanation for every question. This is a free MDCAT Sindh / DUHS past paper — no signup, no ads. Practise it interactively in timed mode, drill more with free MDCAT MCQs, or browse all Sindh / DUHS papers.
Attempt this paper interactively →Q1. Enzyme are protected at high temperature by:
- A. Freezing tolerance
- B. Super Cooling
- C. Heat Shock Proteins✓
- D. Boiling Tolerance
Explanation: HSPs are widely distributed in cells and participate in a variety of cellular processes to keep cell integrity, maintain protein homeostasis, and response to stresses. They also participate in regulation of cell cycle, apoptosis, signal transduction, and other physiological processes.
Why the other options are wrong
- A. Freezing tolerance describes the ability of plants to withstand subzero temperatures through the formation of ice crystals in the xylem and intercellular space, or apoplast, of their cells.
- B. In supercooling, an object cools below the freezing point without solidification or crystallization. Supercooling is the process of decreasing a liquid's or gas's temperature below the freezing point without allowing it to solidify. This process is also known as undercooling.
- D. This is incorrect.
Q2. Chromosomal Theory of Heredity was proposed by:
- A. George Beadle
- B. Carl Correns
- C. Hershey and Chase
- D. Walter Sutton✓
Explanation: In 1902 and 1903, Sutton and Boveri published independent papers proposing what we now call the chromosome theory of inheritance.
Why the other options are wrong
- A. George Wells Beadle studied corn, fruit flies, and funguses in the US during the twentieth century. These studies helped Beadle earn the 1958 Nobel Prize in Physiology or Medicine. Beadle shared the prize with Edward Tatum for their discovery that genes help regulate chemical processes in and between cells.
- B. He rediscovered and independently verified the work of Mendel in a separate model organism. He also discovered cytoplasmic inheritance, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype.
- C. Hershey and Chase were able to separate the phages into radioactive sulfur-containing protein ghosts and radioactive phosphorus-containing DNA
Q3. In this sub-stage of Meiosis Prophase I, Terminalization occurs:
- A. Pachytene
- B. Diakinesis✓
- C. Diplotene
- D. Leptotene
Explanation: Diakinesis stage of the meiotic prophase shows terminalisation of chiasmata as its distinctive feature.
Why the other options are wrong
- A. The long pachytene stage begins with the completion of synapsis and is associated with further thickening and shortening of chromosomes. During this stage, exchanges of chromosome material between maternal and paternal homologous chromosomes occur by crossing over.
- C. Diplotene stage is characterized by desynapsis and chiasmata formation. In the diplotene stage synaptonemal complex formed during zygotene dissolve and desynapsis of homologous chromosomes start. Homologous chromosomes separate from each other except at the sites of crossing over called chiasmata.
- D. In the leptotene stage, chromosomes become visible in the form of thread-like structures (leptos = thin threads). Chromomeres, the beads-like structure can be seen. The Leptotene stage is also known as the bouquet stage due to the specific alignment of chromosomes in the nucleus.
Q4. A cell division without spindle is:
- A. Amitosis✓
- B. Apomixis
- C. Meiosis
- D. Mitosis
Explanation: Amitosis is direct cell division by simple cleavage of the nucleus, without spindle formation or the appearance of chromosomes.
Why the other options are wrong
- B. Apomixis is the process of asexual reproduction through seeds that is increasingly being viewed as a deregulation of sexual reproduction rather than an independent pathway.
- C. Meiosis is a type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes (the sex cells, or egg and sperm).
- D. Mitosis is the process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division. Mitosis is generally followed by equal division of the cell's content into two daughter cells that have identical genomes.
Q5. This is present in RNA but not in DNA.
- A. Uracil✓
- B. Guanine
- C. Adenine
- D. Cytosine
Explanation: Uracil is the nitrogenous base present only in RNA, but not in DNA. Thymine is in DNA. DNA have thymine, guanine, adenine and cytosine. Thymine is replaced by uracil in RNA.
Why the other options are wrong
- B. Uracil is the nitrogenous base present only in RNA, but not in DNA. Thymine is in DNA. DNA have thymine, guanine, adenine and cytosine. Thymine is replaced by uracil in RNA.
- C. Uracil is the nitrogenous base present only in RNA, but not in DNA. Thymine is in DNA. DNA have thymine, guanine, adenine and cytosine. Thymine is replaced by uracil in RNA.
- D. Uracil is the nitrogenous base present only in RNA, but not in DNA. Thymine is in DNA. DNA have thymine, guanine, adenine and cytosine. Thymine is replaced by uracil in RNA.
Q6. The multiple effects of a single gene is termed as:
- A. Polygenic inheritance
- B. Pleiotropy✓
- C. Multiple Alleles
- D. Incomplete Dominance
Explanation: Pleiotropy: One Gene Can Affect Multiple Traits.
Why the other options are wrong
- A. Polygenic Inheritance refers to an inheritance of a single phenotypic trait controlled by multiple independent genes.
- C. Multiple alleles can be defined as a series of forms of a gene situated at the same locus of homologous chromosomes. According to Mendel, each gene had two alternate forms or allele morphs are being dominant and the other being recessive.
- D. Incomplete dominance pertains to the genetic phenomenon in which the distinct gene products from the two codominant alleles in a heterozygote blend to form a phenotype intermediate between those of the two homozygotes.
Q7. If the sequence of base in fits Partner in the duplex is: one chain is ATTGCAT, the base sequence
- A. ATAGCAT
- B. TAACGTA✓
- C. GCCATTA
- D. AATGCAT
Explanation: Complementary base pairing is the phenomenon where in DNA, guanine always binds to cytosine and adenine always binds to thymine. Guanine and cytosine share three hydrogen bonds while adenine and thymine always share two hydrogen bonds. RNA replaces thymine (T) with a different pyrimidine base called uracil (U).
Why the other options are wrong
- A. Complementary base pairing is the phenomenon where in DNA, guanine always binds to cytosine and adenine always binds to thymine. Guanine and cytosine share three hydrogen bonds while adenine and thymine always share two hydrogen bonds. RNA replaces thymine (T) with a different pyrimidine base called uracil (U).
- C. Complementary base pairing is the phenomenon where in DNA, guanine always binds to cytosine and adenine always binds to thymine. Guanine and cytosine share three hydrogen bonds while adenine and thymine always share two hydrogen bonds. RNA replaces thymine (T) with a different pyrimidine base called uracil (U).
- D. Complementary base pairing is the phenomenon where in DNA, guanine always binds to cytosine and adenine always binds to thymine. Guanine and cytosine share three hydrogen bonds while adenine and thymine always share two hydrogen bonds. RNA replaces thymine (T) with a different pyrimidine base called uracil (U).
Q8. The first line of defence against plants
- A. Endodemis
- B. Cuticle✓
- C. Cortex
- D. Epidermis
Explanation: The first line of defense in plants is an intact and impenetrable barrier composed of bark and a waxy cuticle. Both protect plants against herbivores. Other adaptations against herbivores include hard shells, thorns (modified branches), and spines (modified leaves).
Why the other options are wrong
- A. The first line of defense in plants is an intact and impenetrable barrier composed of bark and a waxy cuticle. Both protect plants against herbivores. Other adaptations against herbivores include hard shells, thorns (modified branches), and spines (modified leaves).
- C. The first line of defense in plants is an intact and impenetrable barrier composed of bark and a waxy cuticle. Both protect plants against herbivores. Other adaptations against herbivores include hard shells, thorns (modified branches), and spines (modified leaves).
- D. The first line of defense in plants is an intact and impenetrable barrier composed of bark and a waxy cuticle. Both protect plants against herbivores. Other adaptations against herbivores include hard shells, thorns (modified branches), and spines (modified leaves).
Q9. Gemination of seed within fruit still to the plant is:
- A. Hypogeal
- B. Imbibed
- C. Epigeal
- D. Viviparous✓
Explanation: Viviparous germination is one in which a seed germinates inside the fruit while it is still attached to the parent plant.
Why the other options are wrong
- A. Epigeal germination indicates the germination of the plant above the ground. Hypogeal germination is an Indicative of plant germination under the ground.
- B. The adsorption of water by hydrophilic-protoplasmic and cell wall elements in plant cells is referred to as imbibition. Imbibition induces seed enlargement, which causes the seed coat or testa to break. Seed germination is the first step of imbibition.
- C. Epigeal germination indicates the germination of the plant above the ground. Hypogeal germination is an Indicative of plant germination under the ground.
Q10. Protecting of flowering by cold treatment given to imbibed seeds is
- A. Vernalization✓
- B. Parthenocarpy
- C. Apomixis
- D. Phototropism
Explanation: The acquisition of ability to flower by cold treatment is called as. Photoperiodism. Vernalization.
Why the other options are wrong
- B. Parthenocarpy refers to the development of fruit without fertilization. The process produces a sterile fruit that lacks seeds. This means that the pollination results in a production of berries that are completely seedless (Colova-Tsolova et al., 2003).
- C. Apomixis is the process of asexual reproduction through seeds that is increasingly being viewed as a deregulation of sexual reproduction rather than an independent pathway.
- D. Phototropism is the ability of the plant to re-orient the shoot growth towards a direction of light source. Phototropism is important to plants as it enhances the ability of plants to optimize their photosynthetic capacity. As discussed above, phototropic response is exclusively controlled by phots.
Q11. Both polynucleotide strands of DNA remain separated by:
- A. 20 A✓
- B. 15 A
- C. 5 A
- D. 2 A
Explanation: The B-DNA is 20 Angstroms wide, and the distance between base sets is 3.4 Angstroms, or 0.34 nm. The base matching of inverse strands is stereo chemically specific, with adenine constantly blending with thymine and guanine constantly blending with cytosine.
Why the other options are wrong
- B. The B-DNA is 20 Angstroms wide, and the distance between base sets is 3.4 Angstroms, or 0.34 nm. The base matching of inverse strands is stereo chemically specific, with adenine constantly blending with thymine and guanine constantly blending with cytosine.
- C. The B-DNA is 20 Angstroms wide, and the distance between base sets is 3.4 Angstroms, or 0.34 nm. The base matching of inverse strands is stereo chemically specific, with adenine constantly blending with thymine and guanine constantly blending with cytosine.
- D. The B-DNA is 20 Angstroms wide, and the distance between base sets is 3.4 Angstroms, or 0.34 nm. The base matching of inverse strands is stereo chemically specific, with adenine constantly blending with thymine and guanine constantly blending with cytosine.
Q12. Dark zone of oceanic region is:
- A. Euphotic
- B. Profundal
- C. Neritic
- D. Aphotic✓
Explanation: The aphotic zone is also known as the "midnight zone". Since sunlight doesn't reach this part of the ocean, this area is entirely black and devoid of daylight. Some sea creatures are bioluminescent, meaning their bodies emit light that allow them to see in the area they inhabit.
Why the other options are wrong
- A. The upper 200 meters of the ocean is called the euphotic, or "sunlight," zone. This zone contains the vast majority of commercial fisheries and is home to many protected marine mammals and sea turtles. Only a small amount of light penetrates beyond this depth.
- B. The profundal zone is a deep zone of an inland body of freestanding water, such as a lake or pond, located below the range of effective light penetration. This is typically below the thermocline, the vertical zone in the water through which temperature drops rapidly.
- C. Neritic zone, shallow marine environment extending from mean low water down to 200-metre (660-foot) depths, generally corresponding to the continental shelf. Neritic waters are penetrated by varying amounts of sunlight, which permits photosynthesis by both planktonic and bottom-dwelling organisms.
Q13. The cotyledon in monocot seed is called:
- A. Epicotyl
- B. Scutellum✓
- C. Coleoptile
- D. Coleorhiza
Explanation: In monocot, the first cotyledon is called scutellum while the second cotyledon is rudimentary and is called. A. radicle.
Why the other options are wrong
- A. The epicotyl is a segment of the embryonic axis that runs between the cotyledons and the plumule, whereas the hypocotyl is a segment of the embryonic axis that runs between the cotyledonary node as well as the radicle. The main distinction between epicotyl & hypocotyl is this.
- C. Coleoptiles are cylindrical organs that ensheath the first leaf and shoot apex in grass seedlings. They help in the emergence of the first leaf (and shoot apex) by protecting it during its passage through the soil. On emergence, the first leaf breaks through the coleoptile tip.
- D. The coleorhiza or root sheath is a layer of tissue that surrounds the inner roots of the seed and prevents monocotyledonous plants. Coleorhiza is the first part that remains on the ground and develops from seeds that are not green in color.
Q14. Example of ecosystem having lotic water is
- A. Waterfall✓
- B. Toitings
- C. Pond
- D. Swamp
Explanation: Lotic ecosystems are characterized by flowing waters. Examples include rivers, streams, brooks and springs.
Why the other options are wrong
- B. Lotic ecosystems are characterized by flowing waters. Examples include rivers, streams, brooks and springs.
- C. Lotic ecosystems are characterized by flowing waters. Examples include rivers, streams, brooks and springs.
- D. Lotic ecosystems are characterized by flowing waters. Examples include rivers, streams, brooks and springs.
Q15. In guttation plants lose excess water in the form of liquid from special pores on leaves called:
- A. Air pores
- B. Cuticle
- C. lenticel
- D. Hydathodes✓
Explanation: Guttation exudes water through pores called hydathodes. Bleeding happens through the cut surface of plants. Transpiration is the loss of water vapor from the aerial parts of the plant.
Why the other options are wrong
- A. Guttation exudes water through pores called hydathodes. Bleeding happens through the cut surface of plants. Transpiration is the loss of water vapor from the aerial parts of the plant.
- B. The aerial surfaces of plants are covered by a protective barrier formed by the cutin polyester and waxes, collectively referred to as the cuticle. Plant cuticles prevent the loss of water, regulate transpiration, and facilitate the transport of gases and solutes.
- C. A lenticel is a porous tissue made up of vast intercellular gaps between cells. On stems and roots, lenticels appear as elevated circular, oval, or elongated patches. Lenticels allow gases to pass between the atmosphere and the organs' interior tissues.
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