Tutor profile: Savannah E.
Subject: Biomedical Science
What is one way that Natural Killer cells identify their targets? Explain.
When a cell is infected with a virus, the virus will often cause the cell to downregulate the surface expression of MHC1 which serves to present proteins from inside the cell to surveilling immune cells. Natural Killer (NK) cells have inhibitory receptors on their cell surface that recognize MCH1 and prevent the NK cells from killing the cells in the body. If a cell is infected with a virus and MHC1 is downregulated, then the NK cell does not get the inhibitory signal and thus a target for cell killing is identified. This method is called the missing self hypothesis.
Subject: Basic Chemistry
Does ionization energy increase or decrease as you move up within a group on the periodic table of elements? What is the reason behind this?
It increases. As you move up within a group on the periodic table, the outer electron shell is closer to the nucleus and thus the electrons within that shell feel a stronger pull from the positively charged protons in the nucleus. This stronger pull makes it harder to eject electrons from the outer shell and to do so requires more energy, thus the closer the outer shell to the nucleus, and the higher up in the group the element, the larger the ionization energy.
Can the DNA in mitochondria become mutated and if so, how does this impact the offspring of a male with a mutation?
Mitochondrial DNA can become mutated just like our genomic DNA. Mitochondria replicate separately from the rest of the cell and if the DNA in one mitochondrion gets mutated that does not mean that all the mitochondria in the cell will have the mutation. During fertilization, in most cases, all the mitochondria from the sperm are destroyed and thus the offspring will only have maternal mitochondria. This means that although the father has a mitochondrial mutation, his offspring, with rare exceptions, won't be affected by it.
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