Term
| What are two examples of physiological variation? |
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Definition
Pharmacokinetics - inherited sensitivity to drugs - warfarin has up to a 20-fold variation in effective dosage - based on warfarin metabolism and the target protein
Colour vision |
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Term
| What is colour vision mediated by and what codes for them? |
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Definition
| Red/green/blue cone cells - red and green opsin genes on X chromosome, blue opsin gene on chromosome 7 |
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Term
| What are the common variants of loss of full colour vision |
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Definition
Dichromacy - loss of red or green opsin
Anomalous trichromacy - shift in spectrum of red or green |
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Term
| What is a defect in the red pigment called? |
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Definition
| A protanomaly, disease is protanopia, people are protans |
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Term
| What is a defect in the green pigment called? |
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Definition
| Duetanomaly - people are deutans, disease is deutanopia |
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Term
| How are red-green colour vision defects inherited? |
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Definition
|
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Term
| What are the proportions of people with variant colour vision? |
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Definition
| 50% deutans, the rest split between three equal parts |
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Term
| What is the normal structure of the red/green opsin genes? |
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Definition
| single red opsin, tandem repeats of 1-3 green opsin genes |
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Term
| How do protans lose red vision function? |
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Definition
| Fusion of the red gene with a green gene |
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Term
| What are the most common ways for deutans to lose green vision? |
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Definition
Deletion of green genes - about 1/3
Normal red and green genes with hybrids - fusions mostly, but certain arease are 'patchy' - possibly due to gene conversion |
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Term
| What is blue cone monochromacy? |
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Definition
| No functional red/green genes due to deletion in the control region upstream, leading to no expression, or loss of function mutations in both red and green genes |
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Term
| What three examples can you give of genetic variation causing variation in appearance? |
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Definition
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Term
| Where is there likely to be a major eye colour gene and which eye colour appears to be dominant? |
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Definition
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Term
| Why is SLC24A5 important? |
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Definition
| Skin colour gene - fixed in europeans, almost absent from africa/asia - strong signature of selection in surrounding markers -therefore asian skin lightening was due to independent variants at other loci |
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Term
| How is the H locus related to the ABO system? |
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Definition
| It determines the synthesis of H, which is modified by the product of the ABO locus |
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Term
| What is the Bombay phenotype? |
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Definition
| Individuals cannot make the substrate H (they are genotype hh) for modification by the product of the ABO locus, and so appear as O regardless of ABO genotype |
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Term
| How can you tell the Bombay phenotype apart from a natural O blood group? |
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Definition
| Pedigree chart - see it cannot be O |
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Term
| What is the para-Bombay phenotype? |
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Definition
| Antigens are also present in saliva in around 75% of people - this secretion is controlled by Se. Se and H are linked but distinct, so individuals that are Se+/hh have no detectable red cell antigens but have antigens in saliva |
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|
Term
| What are the antigenic differences due to? |
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Definition
|
|
Term
| What are the H molecule, and A/B antigens made by? |
|
Definition
H - fucosyltransferase
A - N-acetylgalactosaminyl transferase
B - galactosyl transferase |
|
|
Term
| What does the ABO locus encode? |
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Definition
|
|
Term
| What does H encode and how are Bombay individuals different? |
|
Definition
| Fucosyl transferase responsible (FUT1), they have a point mutation which inactivates the enzyme |
|
|
Term
| What does saliva secretion of ABO antigens results from? |
|
Definition
| Modification by FUT2 - non secretors have inactivating mutations |
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|
Term
| What blood type is associated with less severe malaria? |
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Definition
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|
Term
|
Definition
| Likely due to bloodborne pathogens and parasites |
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Term
| Why is Rhesus important in birth? |
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Definition
| IF the mother is RH- and the child Rh+, and the mother has been previously immunized to Rh+, either by a previous child or blood transfusion, the mothers immune system will attack the childs red cells - haemolytic disease of the newborn |
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Term
| How can HDN be prevented? |
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Definition
| Identify RH- mothers, give Rh antibodies immediately after the first birth - mops up Rh+ cells without sensitizing mother |
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|
Term
| What are the antigenic determinants for Rh? |
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Definition
C/c,D/d,E/e
D is the major determinant - Rh+ means positive for the D antigen
Two genes - D and CE |
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|
Term
| What is Rh- due to in Europeans? |
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Definition
|
|
Term
| What is Rh- due to in Asians and Africans? |
|
Definition
| RHD is present but not expresesd |
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|
Term
| What methods are available for genotyping SNPs? |
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Definition
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|
Term
| How does LD arise in hapltoypes? |
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Definition
| Mutations creating SNPs arise sequentially |
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Term
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Definition
| The commonest dispersed repeats- about 300bp long each, polyadenylated |
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Term
|
Definition
| Line1 elements, polyadenylated |
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Term
| What are the forms of dispersed repeat variation? |
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Definition
| Absence/presence of dispersed repeats, and internal variation of dispersed repeats |
|
|
Term
| What are recentyl inserted Alus? |
|
Definition
| Present in humans, absent from other primates, polymorphic in humans |
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|
Term
| What age are most alu elements? |
|
Definition
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