Answer:
The correct answer is E. All of the above
Explanation:
Variation in offspring can be contributed by many different events that change the DNA sequence in gametic cells. These events are crossing over, mutation, independent assortment, and random fertilization.
During the gamete formation, the different genes are assorted independently from the other gametes which results in forming various possible combinations of genes in a gamete increasing the genetic variation.
Crossing over occurs during meiosis between the homologous chromosome that results in exchange of genetic material that brings genetic variation in gametes. During random fertilization, the two gametes fuse and genetic material of two different individual comes to make an offspring which forms a genetical different offspring.
Mutation in the gametic cell is transferred to the offspring during fertilization. Therefore all contributes to variation in offspring produced by sexual reproduction.
Answer:
2. plant cell has more defined shape than the shape of an animal cell, because the plant cell has a cell wall that gives it a rigid shape
Answer:
towards the cell, because salt, and the cell may die
Explanation:
1. Dysentery caused by <em>Shigella dysenteriae</em><em> </em>is isolated using MacConkey Lactose agar and Xylose Lysine agar
2. Antibiotic associated diarrhea caused by <em>Clostridium difficile</em> (detection of toxin) is isolated using <em>Clostridium difficile</em> selective medium
3. Dermatophyte infection in the nails is isolated using potatoes dextrose agar
4. Dengue fever by immune response is isolated using minimal essential medium (MEM)
1. Dysentery caused by <em>Shigella dysenteriae</em>
- Collection of fecal specimens and poultry (100) fecal samples collected from were processed according to published protocols.
- Streak one loopful of fecal sample on MacConkey Lactose Agar (MLA) and Xylose Lysine agar
- Incubated at 37 C for 24 hours
- The MLA plates showing the presence of convex and colorless colonies are considered for further identification.
- Similarly, the XLD plates showing appearance of presence of translucent or red colored colonies are taken for further identification.
2. Antibiotic associated diarrhea caused by <em>Clostridium difficile </em>(detection of toxin)
- Mix equal parts of industrial absolute alcohol and the fecal specimen.
- Homogenize using a vortex mixer.
- Leave at room temperature for 1 hr.
- Inoculate on <em> </em><em>Clostridium difficile </em>Selective Agar
- Incubate at 37ºC in a conventional anaerobic gas jar
- Observe after 24-48 hours in anaerobic environment .
- Use gram stain reagent and Malachite green for morphological study.
- Observe positive bacillus cell shape with single or chains(2-6)cell and sub terminal endo spore forming after gram staining
3. Dermatophyte infection in the nails
- Prepare potatoes dextrose agar (PDA)
- Collect clippings from the nail with a sterile scalpel after carefully washing the site with 70% alcohol.
- Dissolved in two drops of 10% KOH on a glass slide, if the sample is thick, use 20% KOH
- Heat the slide few seconds over a spirit lamp, do not allow to boil.
- Observe preparation under a low power of the microscope in reduced light.
- Look out for presence of mycelia fragments and the distribution of spores inside.
4. Dengue fever by immune response
- Dilute blood samples in minimal essential medium (MEM) containing 2% fetal bovine serum (FBS)
- Add diluent to a cultured monolayer of C6/36 cells for 1 hour with gentle rocking in a 28 °C CO2 incubator.
- After 1 hour, remove the inoculum and cells
- Culture for 7 days in MEM with 2% FBS and antibiotics.
- Collect culture supernatant on day 7 and infect a new batch of C6/36 cells
- Repeat the procedure three times to achieve passage 3 (P3) isolates.
Learn more about culturing of microorganisms here:
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