TitleAn experiment testing some of Mendels principles of mutation in fern Ceratopteris richardii.
Abstract: A mature C-Fern spore is a haploid, single cell encased in a spore wall. Upon germination, mitotic divisions give rise to a mature haploid gametophyte or prothallium. When grown in multispore cultures, two types of gametophytes are produced that bear male and/or female sex organs (gametangia), the antheridia and archegonia, respectively. The hermaphroditic gametophyte is the larger of the two and is characterized by a localized notch meristem that results in a heart or cordate shape. The hermaphrodite initially produces the female sex organs and subsequently produces a small number of male sex organs. The tongue-shaped male gametophyte is smaller, lacks a meristem, and only produces male sex organs. This investigation explores how these two types of gametophytes are produced.
Introduction: In this report, an experiment conducted with the aim of testing some of Mendels principles by follow the pattern of inheritance for a trait in the fern Ceratopteris richardii, referred to below as C-fern. The experiment was carried out to determined mutation which is a biological change in or damage of the DNA gene or physical genetic make-up of an organism leading to altering the genetic message carried by the gene. The trait causes chloroplasts within the cells to clump together, giving the plant tissue something of a polka-dot appearance. This organism has an advantage over many others because of the differences in the life cycle in terms haploid cells of the genotype of ferns compared to animals thus constitute the reason why it was preferred against other organism species.
Methods (or Procedure): A small Petri plate, about half filled with nutrient agar was obtained while a careful move maintained not to open the Petri plate to avoid contamination by bacteria and fungi. A grid was drawn on the bottom of the Petri plate with a marker pen to make counting the plants easier. The C-fern spores were sterilized and suspended in distilled water. Upon sterilization of C-fern spores, three drops of spore suspension were carefully added to the growth medium in your Petri plate using a glass pipette. A little air was then gently bubbled into the suspension before drawing it up into the pipette to ensure the spores are thoroughly mixed in the suspension. The spore suspension was gently spread around the surface of the growth medium using one of the sterile glass rods. The amount of time the lid is off the Petri plate was kept to a minimum with the aim of reducing the possibility of contamination. Thereafter, the spores were observed using a dissecting microscope while keeping the Petri plate lid on. The above procedure was repeated to produce 10 Petri plate replicates. After observing the C-fern cultures, the Petri plate was place in a warm humid location under continuous light.
Testing Procedure: When observe the C-fern culture using the dissecting microscope and keeping the lid on, the plants were seen growing from the spores are the gametophyte generation. During this stage, I was able to distinguish between the normal phenotypes and the polka-dot phenotypes. each individual growing in the dish were scored as normal or polka dot and results recorded. This procedure was repeated for each Petri plate replicate. When finished scoring the gametophytes in the Petri plates, 2 ml of sterile distilled water were added to each culture using a sterile pipette. The lid was closed, and the plate tilted back and forth to cover all of the gametophytes with water. During this time, the gametophyte culture was observed with a compound microscope using the low power objective lens, the swimming sperm were visible. Once observation of the plants was done, the Petri plate cover was replaced, and the culture returned to the growth location with continuous light. The counts from all cultures were combined into the total number of gametophytes with a normal phenotype and a total number of gametophytes with a polka-dot phenotype. And evaluation of the observations was carried out using a chi-square test to see if the observed gametophyte phenotypes meet the expected 1:1 Mendelian ratio.
Life cycle of a fern plant (-fern) under study
Discussion (or Conclusion): All of the cells in that C- fern plant contain two sets of chromosomes (the cells are diploid). In terms of its life cycle, this plant is said to be in the sporophyte generation. Within this sporophyte plant, at some time a few specialized cells will divide by meiosis rather than mitosis, producing cells that have only a single set of chromosomes (haploid cells) rather than twos sets. These haploid cells produced from the sporophyte plant are called spores. In ferns, these spores are released from the sporophyte plants to become independently established plants. When these haploid spores germinate and begin to grow by mitosis, a small multicellular plant is produced in which all of its cells contain only a single set of chromosomes. This phase of the plant life cycle is called the gametophyte generation. As the gametophyte fern plant matures, specialized cells, produced by mitosis, will form gametes (either sperm cells or egg cells). When the sperm cells are released from the gametophyte they will swim through a film of water to reach an egg cell, usually on a different gametophyte plant.
After fertilization of the egg by a sperm, a zygote is formed that contains two sets of chromosomes (its diploid). This zygote then begins to divide by mitosis and will grow into a new multicellular sporophyte fern, completing the life cycle. This experiment begins with spores in the ferns life cycle. These are germinated and grown into the fern gametophytes that are then allowed to produce sperm and eggs. The resulting zygote is then allowed to grow into young sporophyte plants. The phenotypes of the haploid gametophytes and the diploid sporophytes will be assessed to determine if inheritance of this trait, polka dot, follows Mendels expectations. The parent fern that produced the spores that were plated was heterozygous for this trait (Pp). Therefore, according to Mendels expectations, half of the spores (so half of the gametophyte plants) to receive the dominant normal allele (P) and half of the spores/gametophytes to receive the recessive polka-dot allele (p), and 1:1 ratio.
These two phenotypes appeared in the gametophyte plants that grew. The numbers of each phenotype were counted in the 10 Petri plates. When the sperm and eggs from the gametophyte generation unite to form new sporophytes, according to Mendels expectations we would see genotypes of PP, Pp and pp appear in the new generation. These would be formed in a phenotype ratio of 3 dominant for every 1 recessive. Both normal and polka-dot phenotypes appeared in the new sporophyte generation. The number of each phenotype were counted in the 10 Petri plates CITATION Les98 \l 1033 (Lesilie G. & Thomas R. Warne).
BIBLIOGRAPHY Lesilie G. & Thomas R. Warne. Laboratory InvestigationWith C- Fern (Ceratopteris richardii).
PhD Thesis. Toronto: Association for Biology Laboratory Education (ABLE) Press, 1998. Document.
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