Genetic Assessment PDF

Genetic Assessment Interphase: G1: the cell individually itself grows S phase: Replication of DNA (s= synthesis) G2: the cell grows some more in preparation for mitosis Checkpoints: One in G1: Checks if the cell is growing well enough, if the DNA is damaged. Second in G2: Checks if the DNA was rep...

Genetic Assessment Interphase: G1: the cell individually itself grows S phase: Replication of DNA (s= synthesis) G2: the cell grows some more in preparation for mitosis Checkpoints: One in G1: Checks if the cell is growing well enough, if the DNA is damaged. Second in G2: Checks if the DNA was replicated correctly back in the S phase Third in M: Checks the stage metaphase to make sure that chromosomes are lined up in the middle correctly and if they are attached to the spindle correctly. G0: resting phase, cells here are still performing cell functions, but they’re not performing to divide. Some cells go here temporarily, maybe if there’s not enough resources around for example. But some cells stay here permanently, which means they will never get to M phase so they will not divide (like neurons) 1. Explain step by step of mitosis - Before mitosis starts the cell needs to duplicate the genetic material into 46 chromosomes and 92 chromatids which happens in interphase. The PMAT - P: Prophase- Is the very first step because it’s the beginning step, the nucleus is still there and it’s going to go away later on but this is a stage. The chromosomes are visible, in fact they’re condensing which means they are thickening and visible. - M (middle): Metaphase- In this stage the chromosomes line up in the middle of the cell. The nucleus has been disassembles, and is no longer there so we got the chromosomes in the middle waiting there - A (away): Anaphase- The chromosomes move away, they are moving to opposite sides of the cell, so they are moving towards the poles of the cells. These chromosomes are not moving by themselves, they have something called spindles, These spindles are made of microtubules fibers that help the chromosomes to the ends. These spindles are attached with a centriole who is located at the ends of the cell. - T (Two, 2): Telophase- The chromosomes are at the complete opposite ends and new nuclei are forming on each side to make these new cells. The nuclei are starting to surround the chromosomes on both sides. - Cytokinesis- is responsible for the final separation into two cells by splitting the cytoplasm which completes after the PMAT mitosis stages  2. Explain step by step of meiosis Meiosis makes sperm and egg cells, also called as gametes in our body. Most of our cells have 46 chromosomes, but there are some that don't have 46 chromosomes, human sperm, egg cells have 23 chromosomes. Meiosis is a reduction division because we have a starting cell that has 46 chromosomes and at the end we only have 23 chromosomes. Before meiosis can start the cell needs to go through interphase first, where the cell is growing, replicating its DNA. The starting cell has 46 chromosomes and that needs to get duplicated into 46 chromosomes but 92 chromatids. Because we are going from 46 chromosomes to 23 chromosomes, cell division needs to divide twice. The PMAT I - Prophase I: This is where the chromosomes are going to condense and thicken, and they are going to line up with their homologous pairs. Homologous means that the chromosomes are approximately the same size and that they contain the same types of genes in the same location. It’s during Prophase I that crossing over occurs, this is when these chromosomes are lined up in homologous pairs, they have this way they can transfer genetic information and exchange it bw each other. These types of chromosomes with transferred genetic material are called recombinant chromosomes, which can eventually contribute to the variety of siblings even if they have the same parents. - Metaphase I (middle): The chromosomes are going to be in the middle of the cell, it's going to be different tho, from mitosis, because they are still going to be in pairs in the middle of the cell so it's not a single file line, they are in pairs in the middle. - Anaphase I (away): The chromosomes are going to be pulled away by the microtubules spindle fibers which are attached with centrioles which are located at the opposite sides of each other. - Telophase I (two): We end with telophase where two newly formed nuclei. - Cytokinesis: Splitting the cytoplasm so two new cells are made. The PMAT II Prophase II: Homologous pairing and the crossing over part does NOT happen again the prophase II. The spindles are starting to form like in prophase I. Metaphase II (middle): The chromosomes are going to line up in the middle, this time they are in a single file line. They are not in pairs as they were in Metaphase I. Anaphase II (away): This time it's the chromatids that are going to get pulled away by the spindles fibers. Telophase II: The nuclei reforming and the 2 cells are each going to divide so we can see that 4 cells are going to be formed. Cytokinesis: Follows by splitting the cytoplasm. 3. Explain the difference bw metaphase I and metaphase II The main difference is that the chromosomes are not in homologous pairs in metaphase II, as they were in metaphase I. 4. Explain the difference bw anaphase I and anaphase II The main difference is that in anaphase I, the spindles were separating the homologous pairs' chromosomes from each other but in anaphase II the spindles were separating the chromatids. 5. How many bivalents, chromosomes, and chromatids would you expect to find in prophase I n= 23 chromosomes 2n= 46 chromosomes 4n= 92 chromatids 6. During which stage of gametogenesis are the homologous chromosomes separated? In anaphase I 7. In which phase of meiosis the chromatids separate In anaphase II 8. In which stage of gametogenesis the number of chromosomes become haploid Telophase II 9. List the differences bw spermatogenesis and oogenesis Feature Spermatogenesis Oogenesis Location Occurs in the testes Occurs in the ovaries start time Begins at puberty Begins during fetal development End time Continues throughout life Completes at menopause Duration Continues and takes about Cyclinal and can take years 64-72 days per cycle (Paused at stages) Primary products Produces four haploid sperm Produces one haploid egg cell cells from each precursor and polar bodies Cytokinesis Equal division of cytoplasm in Unequal division of cytoplasm; all resulting cells egg gets most Cell output Produces millions of sperm Usually one mature egg per daily menstrual cycle Timing of meiosis Meiosis is completed Meiosis I completed at continuously once started ovulation, Meiosis II upon fertilization Resource Allocation Sperm are small, with few Eggs are large, rich in nutrients stored resources for embryo 10. In which phase of meiosis the cells have the least amount of the chromosomal material In prophase I 11. By which process of reproduction the diploid number of chromosomes is restored The diploid condition of an organism is restored by fertilization Cancer cells Cancer cells tend to not know when to stop dividing, which means that they are dividing frequently, the cells are not regulated; they are uncontrolled. Cancer cells can also have another problem which is that they do not communicate with each other healthy cells, they may not be able to carry out normal cell functions, they may not securely anchor themselves like other cells do which can make them more likely to travel somewhere else. Cancer cells have the ability to secrete their own growth hormone. That naked blood vessels divert over to those cancer cells and supply the cancer cells with nutrients, which take nutrients away from healthy cells. Why are cancer cells a bitch? With some cancer cells, there may be genetic links making some cells more susceptible to having problems, these genetic factors might run in families. Exposure to toxins, radiation, or excessive exposure to UV light can be risk factors for some cells to become cancerous. The uncontrolled growth that cancer cells have gives rise to more cells like them, which can develop into a tumor. Some tumors stay put but some do not. Treatments: Scientists try to develop better treatments which include destroying the cancer cells with radiation or medication, such as chemotherapy which will target cells that divide frequently. 3. GAMETOGENES 4. CELL DIFFERENTIATION Stem cells will activate certain areas of the DNA in their process of differentiating into certain types of cells. Transcription factors have a major role in determining which genes are expressed in a cell because a cell that is going to become a skin cell is going to have different areas of genes expressed than a cell that is going to be a for example stomach cell. There are both internal and external cues for stem cells which can involve these transcription factors. Example of an internal cue is transcription factors present in the cytoplasm of the original starting zygote cell, which will eventually be present in the cells that originate from it. The specific location of the stem cell within the developing embryo can matter, because the transcription factors in different areas of the developing embryo can differ in quantity and type, which could impact what a stem cell differentiates into. Examples of external cue signaling from other cells next to it, external cue can also be from environmental effects like temperature. Stem cells are basically unspecialized, undifferentiated cells that can become other cells in our body. But not all stem cells are found in a developing embryo. Stem cells can be found everywhere in our body for example, muscle, skin, liver, bone and so on, these are called somatic stem cells. Totipotent stem cells: Can give rise to any of the 220 cell types in the embryo Pluripotent stem cells: Can give rise to all cell types except the placenta Multipotent stem cells: Can give rise to a limited number of the cell types CELL AGING CELL DEATH Can go through different pathways to ultimately lead to cell death. Apoptosis: Step 1: Initiation Intrinsic pathway- Triggered by internal cell damage, leading to mitochondrial release of proapoptotic factors. Extrinsic pathway- Triggered by external signals where death ligands bind to cell surface receptors. Step 2: Signal Transduction Intrinsic pathway- Pro-apoptotic proteins are activated, causing mitochondrial permeabilization. Extrinsic pathway- Death receptors activation recruits initiator caspases Step 3: Activation of initiator Caspases Initiator caspases like caspase- 8 or caspase-9 gets activated Step 4: Execution Phase Executioner caspases break down cellular components, fragmenting DNA and degrading proteins. Step 5: Formation of Apoptotic bodies Necrosis: The cell shrinks and break into small, membrane-bound pieces Step 6: Phagocytosis Nearby cells engulf the apoptotic bodies, clearing them without inflammation. Necrosis Step 1: Cell Injury Caused by factors like trauma, infection, toxins, or loss of blood supply Step 2: Loss of membrane integrity Damage leads to disruption of the cell membrane, causing an influx of ions and water, which swells the cell. Step 3: Organelle swelling and dysfunction Mitochondria and other organelles swell and lose function. ATP production declines, disrupting cellular processes. Step 4: Enzyme release Lysosomal enzymes leak out and digest cell components, breaking down proteins, lipids, and nucleic acids. Step 5: Cell lysis and contents release The cell membrane ruptures, releasing the cell’s contents into the surrounding tissue. Step 6: Inflammatory response The released contents attract immune cells, leading to inflammation and potential damage to nearby cells and tissues. CELL REGENERATION Regeneration is a process by which the remaining cells of an injured organ regrow to offset the missed cells.