Sarah Hill 0583028
Lab #2 Cells, Chromosomes, and Mitosis
Part 1:
1. What are the various phases that make up the cell cycle?
The period of time before mitotic replication is known as interphase (Campbell et al., 2008, pp 303). The next phase is prophase, where chromosomes divide and copy (Campbell et al., 2008, pp 303). In metaphase, chromosomes move to the centre of the cell and arrange single-file (Campbell et al., 2008, pp 303). During anaphase, sister chromatids break apart and move to opposite ends of the cell (Campbell et al., 2008, pp 303). Finally, during telophase/cytokinesis, the cytoplasm of the cell splits in half and the cell splits into two identical, diploid, daughter cells (Campbell et al., 2008, pp 303).
2. How is
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Score Vicia root top cells. Calculate the mitotic index.
Number of cells in mitosis = 2 (a)
Number of cells in interphase = 48 (b)
Calculate the mitotic index = a/(a+b)=2/(2+48)=0.04
4. Estimate the duration of mitosis.
19 hours = 1140 minutes
Duration of mitosis = (# min cell cyce)x(mitotic index) = (1140min)x(0.04) = 45.6
Part 2:
5. Score 50 Allium root tip cells. Calculate the mitotic index.
Number of cells in mitosis = 30 (a)
Number of cells in interphase = 20 (b)
Calculate the mitotic index = a/(a+b)=30/(30+20)=0.6
6. Estimate the duration of mitosis.
16.5 hours = 990 minutes
Duration of mitosis = (# min cell cyce)x(mitotic index) = (990min)x(0.6) = 594
7. How does mitosis in animal cells differ from mitosis in plant cells?
As observed in the laboratory, there are a number of differences in the mitotic divisions of animal and plant cells. In general, the nucleus of the animal cell seemed to take up less space than that of the plant cell. The chromosomes in the animal cell seemed to be less numerous or less tightly packed when viewed under a microscope. The most distinct difference that was noticed was the difference in the last stage of cell division. The membrane of the animal cell seemed to pinch in the middle and split between the two daughter cells. In comparison, the daughter cells of the plant where observed to be two distinct rectangular cells and no pinching of the cell membrane was observed. Therefore, it can be hypothesised as a result of what was observed in
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Explain how the giant chromosomes are produced and discuss the role of the puffs of protein synthesis. What do the bands represent?
There are large numbers of identical chromosomes in the nucleus of specific species. If these copies line up they will join to form giant chromosomes. The DNA in bands are responsible for particular genetic duties, each band being responsible for a difference task (Miller, 2005). Puffs are enlargements of the bands which are the location of the synthesis of RNA which happens when the genes on specific bands are activated (Miller, 2005).
10. What exactly is a gene? Explain how gene expression is regulated?
Genes pass genetic information from parents to offspring by coding for certain traits. Genes are located on specific loci within chromosomes, which are carried by gametes. In this way, genetic information is inherited (Campbell et al., 2008, pp 296). Gene expression is controlled by transcription, the beginning stage of DNA replication, in which DNA is transcribed into RNA (Campbell et al., 2008, pp 403).
Draw a diagram of earthworm spermatogenesis. Include an
10.4) In animal cells cytokinesis involves the formation of a cleavage furrow which pinches the cell in two. While in plants cells cytokinesis involves the division of cytoplasm by late telophase, so the daughter cells appear shortly after the end of mitosis.
During interphase, the cells in both animals and bacteria carry out their division general functions according to the type of their cells. Unlike in plants, a preprophase group of cytoskeletal proteins emerge at a future location of the cell plate. At prophase stage, duplicated chromosomes compress in a way that can be seen with the help of a microscope. On the other hand, the mitotic spindle is formed at one side of nucleus, whereas in plants, spindle is formed around the nucleus. During prometaphase in animals and bacteria, the nuclear membrane disappears, the chromosomes attach themselves to mictotubules and start to move. In plants, however, the preprophase group dissolves while at metaphase stage, the chromosomes get aligned at the core of the cell. At anaphase, there are fewer differences between animals and plants. The chromosomes shift apart towards the both par...
In telophase, these separate chromatids uncoil to become chromosomes. This division produces two identical cells.
The process of mitosis can take place in either a haploid (23 chromosomes) or a diploid (46 chromosomes) cell. Before a cell can be ready for a mitotic division it must primarily undergo its interphase stage. Following the interphase stage several other stages come into play. These stages are prophase, prometaphase, metaphase, anaphase, and telophase. During each specific stage certain sequences of events take place that assist to the completion of the division.
Transcription factors are proteins that help turn specific genes "on" or "off" by binding to nearby DNA.
“A gene is a segment of DNA or a sequence of nucleotides in DNA that code for a functional product,” Tortora. Microbiology. p. 575. The syllable of the syllable. These genes not only affect our outlook, but also play a role.
A chromosome is made up of two identical structures called chromatids. The process of nuclear division is called interphase; each DNA molecule in a nucleus makes an identical copy of itself. Each copy is contained in the chromatid and a characteristic narrow region called the centromere holds the two chromatids together. The centromere can be found anywhere along a chromosome but the position is the characteristic for a particular chromosome. Each Chromatid contains one DNA molecule. DNA is the molecule of inheritance and is made up of a series of genes. The fact that the two DNA molecules in the sister chromatids, and hence their genes, are identical is the key to precise nuclear division.
The two new pair of centrioles arise from the proximal end of each of the older centrioles, and elongate to reach the same length as the parent centrioles. The original mother and daughter centrioles completely separate from each other, along with their new daughter centrioles to form two new centrosomes. Each of the two resulting centrosomes thus contain one centriol from the older generation and one newly formed centriole (semiconservative replication). The PCM also gets divided between the two new centrosomes. The sequence of steps of the centrosome duplicaiton cycle shows variations in some cells. For example, in Drosophila melanogaster embryo, the PCM divides before the new daughter centrioles are
The process of cell division plays a very important role in the everyday life of human beings as well as all living organisms. If we did not have cell division, all living organisms would cease to reproduce and eventually perish because of it. Within cell division, there are some key roles that are known as nuclear division and cytokinesis. There are two types within nuclear division. Those two types being mitosis and meiosis. Mitosis and meiosis play a very important role in the everyday life as well. Mitosis is the asexual reproduction in which two cells divide in two in order to make duplicate cells. The cells have an equal number of chromosomes which will result in diploid cells. Mitosis is genetically identical and occurs in all living
In this cell though, the nucleus was not present. The plant cells and animal cells were very different. In the plant cells there was motion of cell parts but in the animal cells there was no motion. Also, the nucleus and chloroplast of the plant cell were towards the outside of the cell because the chloroplast can receive sunlight better on the outside of the cell than on the inside. In the animal cells though, the nucleus and cell organelles, were towards the middle of the cell.
The Animal Cell is a little bit different than the Plant Cell for only a couple of reasons. One is how the Plant Cell has a cell wall and the Animal Cell doesn’t. The cell wall protects and gives structure to the cell. Then there is the Nucleus, which serves as a control center for the cell. Inside the Nucleus there are one or more Nucleoli. They are dense, granular bodies that disappear at the beginning of cell division and reappear at the end. Then you have the Cytoplasm. This is the watery material lying within the cell between the cell membrane and the nucleus. The Cytoplasm also contains organelles, which have specific functions in the cell metabolism. Then there are the Golgi Bodies, which serve as processing, packaging, and storage for the cell. These organelles package and ship things out. Another parts of the cell, a very important one in fact, are the Lysosomes. These organelles are used to break things down and contain enzymes.
During prophase I, homologous chromosomes pair and form snynapses. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.
Genes from parents are passed down to their children and this sets up their lifelong development. When a male cell meets with female reproductive cell, they start a process for a new life in a woman’s womb. The sperm has a different copy of the gene and an egg the same and so when they meet, two copies of genes are present and through them a new life begins and it will comprise both genes. From the eyes to the color of the hair, genetics plays a role in a person’s biological make up and development. Genes can predetermine many different characteristics in human development.
Genetics is the passing of characteristics from parents to offspring through genes. Genes are information
During this phase the DNA aka “deoxyribose nucleic acid” clone then forms chromatin. Chromatin is the mass of genetic material that forms into chromosomes. Interphase is divided into smaller parts: G1 Phase, S phase and G2 Phase. Throughout all the phases, the cells continuously develop by producing mitochondria, endoplasmic reticulum, and proteins. The actual division occurs during the S phase bur the G phases are mainly for the purpose of growing. Starting with the G1 phase the cell grows in preparation for certain intracellular components and DNA replication. This phase makes sure the cell is prepared for the process of DNA replication. It reviews the size and environment to ensure that is it ready to go, and cannot leave the G1 until it is complete. But what happens to a cell when it is not complete and cannot exit out of the phase? It will pause and transfer to phase G0. There’s no certain time to be in this phase but it will remain until it reaches the fitting size and is in a supportive surroundings for DNA replication. It will exit either G1 or G0 and there is no other way besides these. Then the cell will advance to the next phase which is the S phase. Synthesis, or more known as S phase is the section of the cell cycle when the DNA is wrapped into chromosomes then duplicated. This is a very important part of the cycle because it grants each of them that is created, to have the exact same genetic