Hbb Eti
Figure 1.20 Sequence variation in HBB. The DNA sequence of HBB has been found to be remarkably diverse, with many nonsynonymous variants resulting in amino acid changes. Single amino acid substitutions have been reported in at least 138 out of 146 codons in p globin with over 335 different single nucleotide changes as well as concurrent variants, insertions, and deletions Huisman et al. 1996 . The portion of the figure showing sequences, genomic location, and SNPs was adapted from a screenshot...
Box Transposable elements and exaptation
There are now a number of examples where relics of transposable elements can acquire functions that are advantageous to their host genome. A neuronal enhancer of the proopiomelanocortin POMC gene is thought to have arisen from a CORE-SINE retro-transposon some 170 million years ago in the lineage leading to mammals Santangelo et al. 2007 . This group of SINEs lost transposable activity about 100 million years ago in placental mammals where their estimated copy number is 300 000 but remained...
DNA transposons a fossil record in the genome
DNA transposons have only relatively recently been recognized in humans Morgan 1995 Oosumi et al. 1995 Smit and Riggs 1996 . They are thought to constitute 3 of the human genome Lander et al. 2001 . Active DNA transposon elements found in species such as Drosophila are characterized by encoding a transposase gene and having terminal inverted repeat sequences to which the transposase enzyme binds. Transposase catalyses transposition by cutting and pasting van Luenen et al. 1994 . The transposase...
Box Phase I HapMap populations
For phase I of the International HapMap Project, 270 individuals from four different populations were recruited. Two groups of individuals of Asian ancestry in geographic terms were genotyped 45 unrelated Han Chinese from Beijing, China, denoted the 'CHB' population, and 45 Japanese from Tokyo, Japan 'JPT' . For the other two populations studied, of African and European ancestry, each comprised of 30 parent-offspring trios a total of 90 individuals one cohort was from Yoruba in Ibadan, Nigeria...
Info Opf
2 3 4 5 6 7 8 9 10 11 12 13 14 15 AMY1 diploid copy number Figure 4.9 Copy number variation of AMY1 and traditional dietary starch intake. Comparison of copy number variation for AMY1 between populations traditionally having diets with high and low levels of starch. Reprinted by permission from Macmillan Publishers Ltd Nature Genetics Perry et al. 2007 , copyright 2007. COPY NUMBER VARIATION, DIET, AND DRUG METABOLISM 119 hunter gatherers such as the Biaka and Mbuti groups from central Africa,...
HLAB and susceptibility to ankylosing spondylitis
By the early 1970s there were growing numbers of reports of association between the possession of particular HLA antigens on the surface of white blood cells and susceptibility to disease, notably coeliac disease, multiple myeloma, lymphoma, systemic lupus erythematosus, and psoriasis. During the course of the year in 1972, independently reproducible and highly significant associations were found between the possession of HL-A1 and HL-A8 and coeliac disease Falchuk et al. 1972 Stokes et al....
Coreceptor ligands and HIV
HIV-1 suppressing factors produced by CD8 T cells were identified in 1995 as the chemokines RANTES regulated on activation normal T cell expressed and secreted , MIP1a macrophage inflammatory protein-1 alpha , and MIPip Cocchi et al. 1995 . These chemokines were found to be natural ligands for the CCR5 coreceptor necessary for macrophage tropic viral entry, and are associated with HIV-1 transmission and disease progression see Fig. 14.4 Gallo et al. 1999 . RANTES inhibits in vitro replication...
Info Oaa
D S1179 D2S1 D7S820 CSF1PO 12 alleles 24 alleles 10 alleles 10 alleles Ulknhih ilHilAUauuL AA Jl A A A A A A A llllllhll D3S1358 THO1 D13S317 D1 8 alleles 10 alleles 8 alleles 9i AMEL D5S818 FGA low FGA high 2 alleles 10 alleles 19 alleles 9 alleles 250bp 300bp 340bp 350bp 250bp 300bp 340bp 350bp LIZ-labelled GS500 DNA sizing standard Figure 7.3 Use of multiple short tandem repeat genotyping in forensic analysis. A Characteristics of 15 STR loci 205 alleles and a sex typing assay simultaneously...
Info Kub
Narcolepsy is a complex neurological disorder characterized by excessive daytime sleepiness Overeem et al. 2001 . In the majority of cases, cataplexy is also present - a dramatic symptom in which there is sudden bilateral loss of postural muscle tone in association with intense emotions such as laughter. Other rarer symptoms of narcolepsy include vivid dream-like experiences during the transition between wakefulness and sleep hypnagogic hallucinations and sleep paralysis, in which patients are...
Malaria parasites oxidative stress and GPD enzyme deficiency
It may seem remarkable that so many genetic variants are associated with resistance to malaria but this is considered to reflect the remarkably strong selective pressure exerted by malaria over recent human history. The enzyme glucose-6-phosphate dehydrogenase G6PD provides protection for the cell against oxidative damage, for example as a result of iron accumulating on the breakdown of haemoglobin by malaria parasites. Inherited deficiency of G6PD is commonly seen Box 13.2 and a striking...
HBB sequence diversity and sickle cell disease
Sequence diversity in the globin cluster plays an important part in the observed clinical heterogeneity in sickle cell disease for affected individuals when an individual inherits the Hb S variant on one allele and a different globin variant on the other. Thus while possessing two copies of Hb S is associated with the most severe disease, having a copy of Hb S combined with a chromosome with a non-functional HBB gene 0 thalassemia may be of comparable severity. Much less severe disease is...
Reviews Cqs
Reviews of subjects in this chapter can be found in the following publications Human genes influencing disease susceptibility and progression Theodorou et al. 2003 O'Brien and Nelson 2004 Resistance to HIV-1 among highly exposed persistently
Box DNA sequencing
In 1977 Maxam and Gilbert published a DNA sequencing method based on different chemical modifications of DNA such as dimethyl sulphate which then allowed cleavage of the DNA only at specific bases Maxam and Gilbert 1977 . The DNA was radio labelled and visualized by electrophoresis on a polyacrylamide gel, generating a ladder of fragments of different lengths terminating for example at 'A' nucleotides. Depending on the specific chemical modification used, other bases could be preferentially...
Hbq I Hba Lucl Hba
Figure 1.26 Deletions removing regulatory elements leading to a thalassaemia. Schematic of a globin cluster and flanking region showing multispecies conserved sequences MCSs and DNase hypersensitive sites DHSs together with deletions affecting regulatory elements that result in a thalassaemia. The shortest region of overlap between the deletions is shown shaded and includes MCS-R1 and 2. Adapted with permission from Higgs and Wood 2008b .
Cytoadhesion and immune evasion host and parasite diversity
After the parasite invades a red blood cell, a race against time ensues in which the parasite seeks to multiply while avoiding detection and destruction by the human immune system. One parasite strategy involves cytoad-herence, parasitized red blood cells sticking to vascular endothelium or other cells to avoid passing through the spleen, which is very efficient at recognizing and removing infected cells from the circulation. This can be achieved by the parasite expressing specific proteins...
Ataagaac Lwu
Cluster of apparent Hardy-Weinberg disequilibrium Figure 4.6 Discovery of segregating deletions using SNP genotyping data. Cluster patterns within SNP genotyping data showing apparent mendelian inconsistency for a family trio, clusters of null genotypes, and clusters of apparent Hardy-Weinberg disequilibrium, provide a 'footprint' suggestive of segregating deletions. Redrawn and reprinted by permission from Macmillan Publishers Ltd Nature Genetics McCarroll et al. 2006 , copyright 2006.
Golden zebrafish mutants led to the identification of SLCA
As an illustration of how a gene locus showing strong evidence of positive selection within a particular population was determined, there are few examples more elegant than the work implicating the gene SLC24A5. Lamason and colleagues utilized the power of studying a model organism to identify a human gene within which the pattern of nucleotide diversity, and in particular a specific nucleotide substitution, played a major role in determining the light skinned pigmentation phenotype observed...
Autophagy and Crohns disease
An unexpected insight into disease pathogenesis was provided by the genome-wide associations found involving autophagy Box 9.6 , specifically with SNPs at ATG16L1 on chromosome 2q37 encoding ATG autophagy-re-lated 16-like protein, and IRGM at chromosome 5q33 encoding the immunity-related GTPase family M see Fig. 9.24 . Hampe and colleagues carried out a nonsynonymous SNP scan involving 7159 informative SNPs in 735 Crohn's disease cases and 368 controls with replication of the observed...
APOBECG an innate host defence mechanism against retroviral infection
Another part of our defence arsenal against retroviral infection after viral entry into cells was identified in humans in 2002 by Malim and colleagues as apolipo-protein B-editing catalytic polypeptide 3G APOBEC3G Sheehy et al. 2002 . It had been recognized since 1987 that the virion infectivity factor Vif protein of HIV-1 was essential for viral infectivity Fisher et al. 1987 Strebel et al. 1987 and that this protein was required to overcome a restriction factor encoded by the host cell Madani...
Copy number variation in health and susceptibility to disease
Submicroscopic structural genomic variation includes genomic alterations involving segments of DNA more than 1 kb in size and typically less than 3 Mb, which result in a change in DNA dosage, referred to as 'copy number variants' Box 4.1 , together with chromosomal rearrangements leading to a change in position or orientation Scherer et al. 2007 . In this chapter the particular focus is on copy number variants that include deletions, duplications, or insertions, and such genomic loci may be...
Lactase persistence in Middle Eastern populations
Consumption of camel milk may have driven selection for an additional major allele associated with lactase persistence among certain Middle Eastern populations in whom the Arabian camel Dromedary camelous is the main domesticated animal used as a source of milk Enattah et al. 2008 . Pastoralist groups in this region, such as among Saudi Arabians, have a high prevalence of lactase persistence, yet the European lactase persistence allele T-13910 is almost completely absent Cook and al-Torki 1975...
Transitions versus transversions
Nucleotide substitutions comprise either transversions or transitions Freese 1959 . The A to T substitution responsible for Hb S is an example of a transversion transversions involve substitutions of pyrimidines for purines, or purines for pyrimidines A C, A T, C- G, G- T . In contrast, transitions involve substitution of a pyrimidine for a pyrimidine C for T and vice versa, C T , or a purine for a purine A G . Based on the number of possible combinations, a ratio of 2 1 in the occurrence of...