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126 Cards in this Set
- Front
- Back
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Biosafety
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the control of organisms etc.
-to prevent harm to self and environment -the control of the processes of modern biotechnology |
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Epigenetics
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"above/over genetics"
-changes in phenotype or gene expression caused by mechanisms other than changes in the DNA sequence -non-genetic factors cause organism's genes to behave or express themselves differently -modification of nucleotides and/or histones can cause these effects |
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Proteomics
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-the analysis of the expression, localization, functions, and interactions of the proteins produced by the genes of an organism
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Bioinformatics
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-the applications of IT to molecular bio
-the creation and advancement of databases, algorithms, computational and statistical techniques, and theory to solve formal and practical problems arising from the management and analysis of biological data |
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genetics
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-the study of genes and how they're spread
-study of how genes function (structure, organization, function, and transmission, biological inheritance, into next generation) |
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inheritance
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how you transmit genes from one generation to the other (not synonymous w/ genetics), because it also involves culture, material things, etc...not FULLY dealing w/ genetics...
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verticle inheritance
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-from one generation to the other
-parents to offspring |
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horizontal inheritance
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-no way to control it
-from parents to "parents" -ex.. "transmosomes" |
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molecular genetics
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-"fathers" are watson and crick
-in 1953 when they developed DNA molecule's structure (w/ Rosalind Franklin's stolen picture) -introns, translation, etc... |
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classical genetics
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deals mainly with transmission of traits and inheritance
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Osteogenesis Imperfecta
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-autosomal dominant disease
-"brittle bone disease" -most cases caused by defects in type I collagen (alpha 1 or 2 chains of type I collagen) -Null mutations produce a milder form of the disease. Missense mutations that act in a dominant negative manner are often perinatal lethal -no cure |
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Type I Osteogenesis Imperfecta
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-mild bone fragility
-blue sclera -hearing loss in 50% of patients -NORMAL STATURE -few bone deformations |
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father of genetics? explain
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-austrian monk gregor mendel
-advanced genetics w/ exp. on garden peas -formulated "fundamentals principles of heredity" -published these exp. results in 1865...his discoveries received no recognition for about 35 years -his conclusions were based on #'s...he was a mathmatician |
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type II osteogenesis imperfecta
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-the perinatal lethal form
-most severe form -a common mutation in the type I collagen formation is the replacement of glycine w/ another AA, and only glycine is small enough to be accomodated in the middle of the triple helix, so poorly formed fibrils are made and are unstable (MOST COMMON IN THIS TYPE OF O.I.) |
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type III osteogenesis imperfecta
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-severe bone fragility
-very short stature -variably blue sclera -dentinogenesis imperfecta common -progressive bone deformities |
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type IV osteogenesis imperfecta
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-short stature
-normal sclera -mild to moderate bone deformity -hearing loss in some patients -dentinogenesis imperfecta common -variable bone fragility |
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Xeroderm pigmentosum
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-autosomal recessive
-variable expressivity -genetic heterogeneity -"abnormal skin pigment" - a disease of faulty DNA repair -exposure to UV radiation gives u potentially harmful PYRIMIDINE DIMERS in the DNA of skin cells -a highly efficient system of enzymes usually repairs these dimers in normal ppl -those w/ the disease don't have this system working properly -neurological abnormalities seen in some cases -skin tumors risk elevated 1000x -usually begins w/ 1st 10yrs of life -can die before age 20 when severe -2 distinct classes of mutations -the repair enzyme mutations occur in the germ line and so can be transmitted to the next generation |
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what are the repair enzymes involved in correcting pyrimidine dimers (that those w/ XP may lack)
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-helicases (unwinds DNA helix)
-endonucleases (cuts DNA @ dimer site) -exonuclease (removes dimer and nearby nucleotides) -polymerase (fills the gap w/ DNA bases) -ligas (rejoins the corrected DNA) |
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Where very first studies of genetics occured
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-Ancient hebrews and greeks
-later medical scholars described many genetic phenomena and proposed many theories...many incorrect |
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-at about the same time [1] formulated his theories of evolution, and his cousin [2], performed family studies on [3] (especially) to understand the influence of heredity on various human traits
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1-Darwin
2-Francis Galton 3-twins |
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genetics today is largely a result of [1] century research
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1-20th
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mendel's principles were rediscovered in [1] by [2] different scientists in 3 different locations. Who were the 3 scientists? This year [3] also discovered the ABO blood group
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1-1900
2-3 3-Landsteiner The three scientists were ~Carl Correns ~Hugo de Vries ~Erich von tschermak |
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in [1] the "first inborn error of metabolism" was described by [2], and this error was called [3]
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1-1902
2-Archibald Garrod 3- Alkaptonuria |
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In [1] the term "gene" was coined by [2] as the basic unit of [3]
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1- 1909
2- Johannsen 3- heredity |
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[1] researched the genetic consequences in radiation in fruit flies
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1- H.J Muller
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Much of the theoretical basis of population genetics was developed by who?
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1. Ronald Fisha
2. J.B.S. Haldane 3. Sewall Wright |
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In [1] who showed that genes were made of DNA?
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1- 1944
Oswald Avery |
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In [1] Watson and Crick specified the physical structure of DNA in their paper [2]
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Basis for molecular genetics
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in [1] the correct number of chromosomes (human) was determined to be [2]
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1- 1956
2- 46 |
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in the [1] technological developments like gene mapping came about
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1960's
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in [1] the human genome project started and it completed mapping the human genome in [2]
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1- 1990
2- 2003 |
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Mendel called "genes" what?
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"factors of inheritance"
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what does chromatin consist of?
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DNA and proteins (histones)
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what are the symptoms/features of XP? (xeroderm pigmentosum)
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-skin is dry and scaly
-extensive freckling -abnormal skin pigmentation |
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Define "gene"
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-a peice of DNA that encodes for MRNA (proteins), tRNA, rRNA
-the genes occupy space in the DNA |
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Define "locus" and the different loci that the teacher covered.
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-"location"
-genes don't occupy only one permanent space in the DNA - we have : ~split genes (divided by introns + other genes) ~overlapping genes ~jumping genes (ex. transposones...no control over where they go in the DNA) |
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True/False---MOST genes are probably like permanent genes.
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True
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Alleles
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the genes on the chromosome that encode for the same trait
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different alleles arise from where?
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mutations (good or bad mutations)
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genome
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all the genetic makeup of anything...species, etc...
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genotype
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Teacher def:
-the genetic makeup of a few genes...for one INDIVIDUAL -the genetic makeup (alleles) of an INDIVIDUAL for a given gene or a few genes Book Def: -the alleles present at a given locus |
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what are the 3 kinds of genotypes?
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-homozygotes (2 alleles are the same)
-heterozygote -hemizygote (only have 1 allele...ex. men have one X and one Y chromosome |
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Phenotype
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-can be expressed physiologicaly, behaviorlly, morphologically
-expression of the genotype in the INIDIVIDUAL -could also depend on the environment |
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dominance
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allele is always expressed
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recessive
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allele can only be expressed if other allele is recessive
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codominance
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when both alleles are expressed
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how many pairs of autosomes do we have?
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22
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sex-influenced inheritance
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a gene that is an autosome, but some are expressed and others are not (ex. male baldness, women's breasts)
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maternal inheritance
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from moms to sons and daughters. (but there have been some few instances where males have been found to transmit it)
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chromosome abnormalities
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parts/whole chromosomes are either missing, extra, or misplaced (ex. down syndrome, klinefelter, turner)
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multifactorial
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environment factors x genetic factors (ex. size/height/weight/volume, hypertension/cancer/bipolar D
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sickle cell anemia
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-chromosome 11
-autosomal recessive -caused by a single missense point mutation that replaces glutamic acid with valine at position 6 of the beta-globin polypeptide chain -autosomal recessive |
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In [1] form the AA substitution of sickle cell anemia alters the characteristics of the hemoglobin molecule such that the erythrocytes assume a characteristic "sickle" shape underconditions of [2]. these conditions are experienced in [3], the tiny vessels whos diameter is smaller than that of the erythrocyte. Normal erythrocytes can squeeze through capillaries, but sickled erythrocytes are less [4] and unable to do so. Also, the sickled erythrocytes tend to [5] to the vascular endothelium. Resultant vascular obstruction produces localized [6], painful [7], and [8] of various tissues, including bone, spleen, kidneys, and lungs.
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1-homozygous
2-low oxygen tension 3-capillaries 4-flexible 5-stick 6-hypoxemia 7-sickle crisis 8-infarctions |
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in sickle cell anemia, premature destruction of the sickled erythrocytes [1] the number of circuating erythrocytes and the [2] level, producting [3]. Also, splenomegaly occurs, but [4] eventually destroy the spleen, producing some loss in [5] function...this contributes to the recurrent [6] infections (especially [7]) that are commonly seen in individuals with SCD and frequent cause of [8]. In North America, it's estimated that the life expectancy of individuals w/ SCD is decreased by about [9] years
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1-decrease
2-hemoglobin 3-anemia 4-infarctions 5-immune 6-bacterial 7-pneumonia 8-death 9-30 |
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Thalassemia
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-autosomal recessive
-2 major groups: alpha and beta -affects the SYNTHESIS of the globulin chain, not the chain itself -when 1 type of chain is decreased in number, the other chain type, unable to participate in normal tetramer formation, tends to form molecules consisting of 4 chains of the excess type only...these are called homotetramers in contrast to heterotetramers normally formed by alpha and beta chains |
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In alpha-thalassemia the [1] globin chains are deficient, so the [2] chains are found in excess. They form homotetramers that have a greatly [3] oxygen-binding capacity producing [4]
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1-alpha
2- beta 3-decreased 4-hypoxemia |
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In beta-thalassemia, the excess [1] chains form homotetramers that precipitate and damage the [2] of RBC precursors (ex. the cells that form the circulating erythrocytes). This leads to premature erythrocyte destruction and [3]
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1-alpha
2-cell membrane 3-anemia |
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Most cases of alpha-thalassemia are caused by [1] of alpha-globin genes. The loss of 1-2 genes have [2] effect. The loss or abnormality of 3 of the alpha genes produces [3] anemia and splenomegaly ([4] disease). The loss of all 4 alpha-genes (seen mainly in [5]) produces hypoxemia in the fetus and [6], a condition where there is a massive buildup of fluid. Severe hypoxemia invariably causes [7] or [8] death. FATAL
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1-deletion
2- no 3-moderately severe 4-HbH disease 5-southeast asians 6-hydrops fetalis 7-stillbirth 8-neonatal death |
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People with beta-globin mutation in one copy of chromosome [1] (heterozygotes) are said to have beta-thalassemia minor. A condition that involves little or no [2] and doesn't ordinarily require [3] management.
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1-11
2-anemia 3-clinical |
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People whom both copies of the chromosome carry a b-globin mutation develop either b-thalassemia major ([1]) or the less serious beta-thalassemia intermedia. Beta-globin may be completely absent ([2]) or it may be reduced to about 10-30% of the normal amount [3].
[2] produces a more severe disease phenotype, but bc disease features are caused by an excess of alpha-globin chains, ppl with [2] are less severely affected when they also have alpha-globin mutations that [4] the quantity of alpha-globin chains. |
1-Cooley's anemia
2-BetaO-thalassemia 3-Beta+ thalassemia 4- decrease |
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B-globin is not produced until after [1], so the effects of B-thalassemia major are not seen clinically until the age of [2]. These patients develop severe [3], if untreated, substantial growth [4] can occur, and death in the first [5] years of life. The anemia cause bone marrow [6], which produces skeletal changes.
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1-birth
2-2-6months 3- anemia 4-retardation 5-10 6- expansion |
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In contrast to alpha-thalassemia, gene [1] are relatively rare in B-thalassemia. Instead, most cases are caused by [2] mutations. Nonsense and frameshift mutations usually produce [3]. Alterations in [4] are often seen also, in addition to mutations in the beta-globin gene itself
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1- deletions
2-single base 3-BetaO-thalassemia |
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If a point mutation occurs at a donor or acceptor site, normal splicing is [1] completely, producing BetaO-thalassemia. Mutations in the surrounding consensus usually produce [2]
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1-destroyed completely
2- Beta+ thalassemia |
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Leber Hereditary Optical Neuropathy
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-missence (single AA change) mutation in protein-coding mitochondrial DNA (mtDNA)
-mitochondrially inherited degeneration of retinal ganglion cells and their axons. -leads to an acute or subacute loss of central vision -affects predominantly young adult males -characterized by rapid loss of vision in the central visual field as a result of optical nerve death. -vision loss typically begins in the 3rd decade of life and is usually irreversible. -males are more commonly affected than females. women tend to develop the disorder slightly later in life and may be more severely affected |
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Hemophilias
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-x-linked (A +B), autosomal recessive (C)
-autoimmune disorder -platelets intact (so minor lacerations don't lead to excessive bleeding) -effects the CLOTTING FACTORS, not the hemoglobin -the most common severe bleeding disorder -caused by deficient or defective factor 8, a key component of the clotting cascade. -fibrin formation is affected resulting in prolonged and severe bleeding from wounds and hemorrhages in the joints and muscles -increase viral infections due to blood transfusions -factor 8 gene has been mapped to the distal long arm of X chromosome |
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In hemophilic patients, those with nonsense mutations are [1] hemophiliacs, those with missence mutations are [2] hemophiliacs
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1-severe
2- mild |
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Hemophilia A (Classical Hemophilia) affects clotting factor [1] and it is a [2] trait. Hemophilia B (Christmas Disease) affects clotting factor 9, it is [3] severe than A, and it is a [4] trait. Hemophilia C affects clotting factor [5], and it is a [6] trait.
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1-8
2-x-linked 3-less 4-x-linked 5-11 6-autosomal recessive |
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Duchenne's Muscular Dystrophy
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-Dystrophin (DMD)- deletions
-x-linked recessive -caused by multiple loss-of-function mutations in muscle protein -fatal, most severe, most common -no cure -keratin kinase increases when muscles die -affects young males bc x-linked -XP 21 gene mutation -Dystrofin protein is destroyed (it connects cytoskeleton of cell with integral proteins that then connect to the membrane -33% are new mutations |
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DMD covers approx. 2.5 Mb of DNA, making it the [1] gene known in humans. The amino terminus of dystrofin binds [2], a key cytoskeletal protein. The carboxyl terminus binds a complex glycoprotein [3] that spans the cell membrane and binds to extracellular proteins. Lacking dystrophin, the muscle [4] as they're stressed by muscle contractions.
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1-largest
2-F-actin 3-dystroglycan-sarcoglycan complex 4-dies |
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Becker Muscular Dystrophy
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-x-linked recessive
-less severe and common than DMD -progression also much slower w/ onset at 11 years of age -some never lose their ability to walk |
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BMD and DMD are caused by different mutations at the same [1], which is an example [2]. Both diseases usually result from [3] or [4], which produce frameshifts (mostly) in DMD and in-frame alterations (mostly) in BMD.
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1-locus
2-allelic heterogenecity 3-deletions 4-duplications |
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Cystic Fibrosis
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-autosomal recessive characterized by variable expressivity, and genetic heterogeneity
-gene responsible is in chromosome 7q -this gene encodes a protein product labeled the "cystic fibrosis transmembrane regulator" (CFTR) -85% of patients have pancreatic insufficiency -95% of males are sterile -obstruction of lungs by heavy, thick mucous -abnormal sweat glands, so high levels of chloride in sweat -in more than 90% of CF pts there is death from pulmonary disease |
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CFTR forms cyclic AMP-regulated [1] ion channels that span the membranes of specialized epithelium cells. They're also involved in regulating the transport of [2] ions across epithelial cell membranes. Defective ion transport results in [3] imbalances, depleting the airway of water and producing the thick, obstructive secretions seen in lungs and [4]
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1-chloride
2-Na 3-salt 4-pancreas |
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The most common CF mutation (there are more than 1,000 different mutations) is a [1] base deletion that results in the loss of a [2] molecule at position [3] of the CFTR protein (delta F508). delta F508 accounts for nearly [4] of all CF mutations.
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1-3
2-phenylalanine 3-508 4-70% |
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Huntington Disease/"Chorea" (dance)
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-Gene/defect: Huntingtin (HD)- CAG repeat expansion w/in exon 1
-chromosome 4 -gain-of-function mutation -shows anticipation -autosomal dominant -1/20,000 ppl of European descent -usually presents b/n ages 30-50 -progressive loss of motor control, loss of brain neurons/psychiatric problems, -early sign is decreased glucose uptake in the brain |
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The area MOST noticeably damaged is the [1] in HD. As in many neurological disorders, patients experience difficulty swallowing, [2],...and this is the most common cause of death. Affected [3] appear to display exactly the same clinical course as [4] (in contrast to most dominant disorders, in which homozygotes are more severely affected.) Therefore, mutation causes a [5] of function.
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1-corpus striatum
2- aspiration pneumonia 3-homozygotes 4-heterozygotes 5-gain |
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HD is the [1] genetic disease mapped to a specific chromosome using an RFLP marker. James Gusella et al mapped the disease gene to chromosome 4 in [2]. The mutation is a [3] expanded repeat located w/in the cloning portion of the gene. The normal repeat ranges from [4], 27-25 repeats are [5] but can transmit larger # of repeats to their kids. [6] or more copies of the repeat cause disease. 36-41 repeats have [7] penetrance
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1-first
2-1983 3-CAG 4-10-26 5-unaffected 6-36 7-incomplete |
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In HD, the higher amount of repeats leads to [1] age of onset. When males transmit disease there are [2] repeat expansions. The gene product is [3], which is involved in the [4] of vesicles in cellular secretory pathways.
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1-earlier
2-more 3-huntingtin 4-transport |
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Fragile X Syndrome
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-X-linked dominant (females less severely affected)
-inheritance characterized by anticipation gene defect: FMR1-CGG trinucleotide repeat expansion in 5' untranslated region of the gene (expansion occurs exclusively in the mother) -boys w/ syndrome have long faces, prominent jaws, large ears, large testis, and are likely to be mentally retarded -can be manifested in females; multistep mechanism |
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Huntingtin is necessary for normal production of brain-derived [1] factor. CAG repeats makes a lengthened series of [2] residues near huntingtin's [3] terminal. The precise role of the expanded glutamine tract in disease cause is [4], but it leads to a buildup of toxic [5] aggregates w/in or near neuronal nuclei. Buildup correlated w/ early [6] death that is characteristic of HD.
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1-neurotrophic
2-glutamine 3-amino 4-unclear 5-protein 6-neuron |
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Marfan Syndrome
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-chromosome 15 and 5
-gene FBN1 (fibrillin-1 gene) -Protein: microfibril-forming CT protein -Autosomal dominant (dominant negative effect) -Pleitropy -abnormalities of the skeleton, heart, pulmonary system,and joints. -congestive heart failure frequent cause of death |
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Retinoblastoma
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-chromosome 13
-heredity: reduced penetrance -pRb gene (tumor suppressor) -bilateral and multicentric -characterized by malignant eye tumors and affects 1/20,000 children. -the tumor begins during embryologic development and presents itself by the age of 5 -the reason for reduced penetrance is that 2 events (mutations) must occur in order to show symptoms for the disease. First, inherit a mutation on one member of the chromosome 13 pair. Second, a somatic mutation must occur in the same region of chromosome 13 in a developing retinal cell of the fetus and has a low probability of occurring. |
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Neurofibromatosis
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-autosomal dominant
-caused by multiple loss-of-function mutations in a signaling molecule type 1- chromosome 17 (mutation in type 1=somatic mosaicism) type 2- chromosome 22 (rarer and no neurofibromas, and encodes a tumor suppressor protein called merlin or schwanomin) protein (NF1): Neurofibromin (tumor suppressor) gene defect: microdeletion at 17q11.2 involving the NF1 gene. UV endonuclease deficiency (type 1) -characterized by numerous benign tumors of the PNS -50% are new mutations -cafe au lait spots, increase tumor susceptibility -good example of variable expression -penetrance is 100% |
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Down Syndrome
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-Trisomy 21
-non-segregation at Chromosome 21 |
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Patau Syndrome
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Trisomy 13
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Klinefelter's Syndrome
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-47 XXY
-Males |
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Edward's Syndrome
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-Trisomy 18
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Turner Syndrome
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-45 X
-females -nondisjunction in sex chromosome |
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Noonan Syndrome
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1
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XYY Syndrome
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-47 XYY
-Males |
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XXX Syndrome
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-trisomy X (XXX)
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Prader Willi/Angelman Syndrome
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-Microdeletion of the PWS region and AS gene
-chromosome 15 -can also be caused by uniparental disomy involving chromosome 15 -These type of diseases are due to genomic imprinting. -The sex of the parent will influence in the disease because the way the chromosome is expressed in the offspring. The sex of the offspring does not influence in the expression of the disease. -Epigenetic effects can lead to methylation and cause the disease. -mother (angelman)-short stature, severe mental retardation, spasticity, seizures, character. stance -father (prader...): obesity, excessive gorging, small hands, feet, hypogonadism, mental retardation |
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Blending Inheritance
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used to be believed and mendel proved that it was wrong, with his Factors of Inheritance.
-He crossed sweet peas |
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1st mendelian law
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-Dominance/Recessive
-opposed blending inheritance -implies that genes are independent entities, though not always expressed, and that each individual has 2 gene copies -looking at the numbers he concluded that we needed to have 2 copies of the same trait -exception to this law is CODOMINANCE |
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2nd mendelian law
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-Law of Segregation
-those 2 copies must seperate before going to the offspring and each offspring gets 1 from each parent -exception is failure to segregate (abnormal) |
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3rd mendelian law
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-Independent Assortment
-How alleles seperate and combine with other alleles of different genes -exception to this law are alleles on the same chromosome with a reduced rate of recombination and those that are very close not segregating at all |
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Backcross
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technique used to determine the genotype of an individual with the dominant phenotype
-the individual is crossed w/ a known homozygous recessive |
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Hemizygous
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gene present in a single copy (ex. Y chromosome)
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Heteroplasmia
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-existence of differing DNA sequences at a locus within a single cell, as in mitochondrial genes, also several alleles within single organism for one gene
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autosomal inheritance
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-aka mendelian
-assumes dominant and recessive alleles and SEX has no influence in the outcome |
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Lyons Hypothesis
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A proposal, now verified, that one X chromosome is randomly inactivated in each somatic cell of the normal female embryo (lyonization), resulting in a Barr body
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Pleitropy
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-presence of genes that have more than one discernable effect on the body
-one gene influencing several traits. A mutation at this gene will result in all traits affected (Marfan's syndrome) |
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Heterogeneity
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refers to the causation of teh same disease phenotype by mutations at different loci
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Locus heterogeneity
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condition occurs due to a mutation at either of a group of genes as in Osteogenesis Imperfecta
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Silent Mutation
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DNA changes do NOT cause a change in the resultant protein due to the redundancy of the genetic code
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Missence mutation
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A type of mutation that results in a single AA change in the translated gene product (ex. SC, and CF)
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Nonsense mutation
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a type of mutation in which an mRNA STOP codon is produced, resulting in premature termination of translation, or removed, resulting in an elongated protein product
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Frameshift mutation
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An alteration of DNA in which a duplication or deletion occurs that is not a multiple of three base pairs, resulting in changes in entire code from that point.
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Delayed onset of expression
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the disease does NOT manifest until later in life as in Huntington's disease
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Reduced Penetration
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genotypes in a population do not express the condition to its fullest capacity
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VAriable expression
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among those with a specific genotype, there's a gamut of degrees in the severity of the disease from mild to severe and even death
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Genetic imprinting
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the same genetic deletion causes a different syndrome depending on which parent passed it down
-ex. Prader-Willis syndrome is inherited from the father while the same deletion coming from the mother is called Angelman Syndrome. -The symptomatology is different in each |
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Anticipation
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describes a disease in which every generation that the disease is passed on, it becomes worse with an earlier onset
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Consanguinity
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-mating between closely related individuals in which offsprings have a higher probability to inherit recessive alleles which pair up to manifest disorders
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Incomplete Dominance
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manifested as a different phenotype than either parent in the offspring
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Gene flow
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exchange of gene w/n different populations
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Founder effect
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a large shift in gene frequencies that result when a small founder population which contains limited genetic variation, is derived from a larger population.
-It can be considered a speical type of "genetic drift" |
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Multifactorial inheritance
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polygenic; diseases that are influenced by genetics and environment in which the genetic element involves several genes (hypertension and diabetes)
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Penetrance
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refers to how many people are affected despite having the genetic make-up
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The possible causes of variable expression
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-environment causes different expression
-gene regulation: variability in controlling sequences -epigenetic effects: same gene with same sequence...but maybe methylation causes changes...and too much may inactivate the gene |
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Karyotype
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the characteristic chromosome complement of a eukaryotic species
-labeled by: 1. size 2.shape (metacentric, submetacentric) 3.bending pattern |
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The types of chromosome abnormalities
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-NUMERICAL
~"true ploidy" aka Euploidy...haploid, diploid ~"not true ploidy" aka Aneuploidy...not whole sets are missing...monosomy 2n-1, trisomy 2n+1, tetrasomy 2n=2 -STRUCTURAL ~in same position but may be backwards |
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The causes of chromosome abnormalities
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Deletions
Insertions (ex. translocation) Duplications |
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Describe 2 types of translocations
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1. Robertsonian (the short arm of chromosome cut and joined to another cut chromosome)
2. Annular (circular cut and left w/ sticky ends) |
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Gene/Defect of XP?
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-Anyone of the nine genes involved in nucleotide excision repair (locus heterogeneity)
-Ptch amd p53 affected -chromosome 9 |
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Colorblindness
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-x-linked recessive
-their expression in females and males is not the same bc the genes on the Y chromosome don't exactly pair up with the genes on the X. -X-linked recessive genes are expressed in females only if there are two copies of the gene (one on each chromosome)., however, for males, there only needs to be one copy of an X-linked recessive gene in order for the trait or disorder to be expressed. |
