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21 Cards in this Set
- Front
- Back
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What do point mutations along the "rigid interface" do to hemoglobin? (i.e. proline in the wrong place)
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causes the hemoglobin to become unstable and precipitate. RBCs are filled with precipitated hemoglobin and are removed from spleen causing anemia
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What are the two scenarios if there is a mutation in the pocket where the heme group is contained?
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1) lose entire heme group, you can't carry oxygen as well
2) heme pocket becomes more flexible allowing H20 to enter, oxidizing iron to from methemoglobin (which also doesn't carry oxygen as well) |
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What is the difference between the hemoglobinopathies and thalassemias?
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Thalassemias is not caused by an abnormal chain but by a decreased production of a chain.
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What are some common characteristics seen with all thalassemias:
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microcytosis: low MCV, hypochromic
basophilic stippling |
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Why are thalassemias hemolytic?
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if you are deficient in one type of chain, you have an excess of another to compensate. This excess will precipitate and damage the membrane of the RBC.
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A normal person has __ total genes for alpha chains.
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4 (2 from each parent)
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What happens if you lose 1 gene for the alpha chain?
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May not have clinical presentation. A reduced MCV. This is called ALPHA THALASSEMIA MINIMA.
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What are the TWO possibilites if you lose 2 genes for the alpha gene?
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1) Lose one from each chromosome -- Type 2
2) Lose two from the same chromosome -- Type 1 |
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Type 1 Thalassemia is fairly common in people of ___ descent.
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Asiatic
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What happens if you lose 3 genes for the alpha chain?
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significant anemia and presence of Hemoglobin H
Hemoglobin H - tetramer of beta chains that does NOT carry oxygen |
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What happens if you lose 4 genes for the alpha chain?
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not compatible w/ life, problem in asiatic groups
around birth, start making gamma chains that form tetramers called Hemoglobin Bart's |
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Beta thalassemias (BT) are not usually caused by gene deletion but a ______.
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point mutation w/in gene
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If the mutation in BT is in an exon, the beta chain is ____.
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never produced b/c mRNA will be corrupt
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If the mutation in BT is in an intron, the beta chain is ____.
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put together incorrectly due to a splicing error
decreased amount o quality mRNA |
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The beta gene is located near ___ and ___ hemoglobin regions. If there is a problem in the beta region, this can lead to _____ of these genes.
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delta and gamma
amplification |
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In a BT with a high level of fetal hemoglobing, what two things can happen?
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1) variation in cell to cell over how much fetal hemoglobin is produced
2) condition known as Hereditary Persistence of Fetal Hemoglobin, where individual produces almost 100% fetal hemoglobin, this is fine |
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Why is there no good way to diagnose AT in a lab?
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no compensatory hemoglobin chains are produced, so electrophoresis is useless
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Why in a Sickle Cell Trait (SCT) patient would you find 60% A hemoglobin and 40% Sickle hemoglobin instead of 50/50?
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Because affinity btwn normal chains is higher than affinity btwn abnormal and normal chains.
Also, RBCs w/ abnormal pairings have a shorter lifespan so looking at the total demographic, you see more normal hemoglobin. |
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What happens when someone gets Hemoglobin S and AT?
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the smaller amount of alpha chains will have higher affinity for NORMAL beta chains. the excess beta S chains will form tetramers, etc. and degenerate
Therefore a person w/ SCT and AT is in better shape than just SCT. |
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What happens when someone gets Hemoglobin S and BT?
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Relative excess of beta S chains (depression of regular chains) which combine w/ alpha chains
This leads to a worse phenotype than SCT alone. |
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A person inherits SC and HPFH?
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do very well b/c fetal hemoglobin prevents sickling of RBCs
depends on distribution of fetal hemoglobin |
