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89 Cards in this Set
- Front
- Back
Cystic Fibrosis is..?
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a fatal genetic disorder
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cause of CF?
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a gene on chromosome 7 that provides the instructions for building a plama membrane protein called CFTR
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CF is a result of
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a faulty CFTR gene is inherrited from both parents
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CF is usually fatal before..?
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the age of 30
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symptoms of CF
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thickened mucus clogs airways, infections develop from bacteria growing in the mucus (normally die of infections)
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people who are ___ are guaranteed to get CF
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homozygous recessive
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treatments for CF
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physiotherapy- thumping on the back and chest to loosen mucus
antibotics-to cure infections |
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gene-chromosome connections
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1.particular locus for each gene
2.a diploid cell has homologous pairs of chromosomes:one from each parent 3.crossing over occurs during meiosis 4.genes in a diploid cell have two alleles 5.independent assortment of chromosomes |
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linkage
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distance is short between chromosomes they are "linked"
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the closer chromosomes are
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less likely to be seperated during crossing over, tend to stay together
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karyotype
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visualizes the chromosomes/gives a portrait of chromosomes in a cell
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a karyotype is..?
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the outward appearance of chromosomes
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in a karyotype you..
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extract cells and grow in tissue cultures
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once cell is culture is established what is added?
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colchicine is added to stop mitosis at metaphase
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after the colchince is added..?
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centrifuge to move cells to bottom of the test tube, add saline and a fixative to the cells
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last step for karyotype
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visualize under microscope, photograph one cell, enlarge picture, arrange chromsomes
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sex chromosomes carry?
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genes associated with sexual traits
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human sex chromosomes
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x chromosome and y chromosome
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X chromosome
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x chromosome- XX (female), most genes deal with nonsexual characteristics, genes refered to as X-linked genes
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Y chromosome
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Y chromosomes- XY(male), gender determined by SRY gene(when gene is expressed testes form in the embryo), genes are refered to as Y-linked genes
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females have two x chromosomes, are both active?
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one x is inactivated
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x inactivation
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most or all of one of a females x chromosomes are turned off soon after first division of zygote, inactivated x is condensed into a Barr body
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incontinentia pigmenti
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x-linked disorder, darker patches of skin are visible in tissue where the mutated x chromosome is active
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sex influenced traits
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appear more often in one gender than the other
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where are genes for sex influence traits located?
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on autosomes
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example of sex influenced trait
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patterened baldness, males are heterozygous, females must be homozygous recessive
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sex-limited genes
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males and females inherit the same genes (on the x chromosome) but only the genes appropriate for the persons gender are turned on
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example of sex-limited genes
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mans beard or a womans breast
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pedrigee chart
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tracks several generations of a family, showing who exhibited the trait being investigated
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pedrigees are often used to?
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identify those at risk of trasmitting or developing the trait in question
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huntingtons disease
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nervous system progressively deteriorates
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Who constucted a pedigree for a huge family in venezuela? (about 10000 people)
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Nancy Wexler
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genetic abnormality
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deviation from the average (6 toes)
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genetic disorder
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causes mild to severe medical problems
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syndrome
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set of symptoms that usually occur together are characterize a disorder
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humans are carries of how many lethal genes?
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3-8 lethal genes
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genetic analysis
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determine genotype or each parent
use family pedigrees one the extent of the risk has been deteremined is is the same for each pregnancy |
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recessive alleles:
parents are heterozygous parents are homozygous |
hetero- 25% chance of offspring being homozygous recessive
homo- 100% of the offsping will have the trait |
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Inherited recessive traits on autosomes cause what disorders?
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cystic fibrosis, phenylketonuria, tay sachs disease
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Cystic Fibrosis
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faulty CFTR gene
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Phenylketonuria
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abnormal build up of the amino acid phenylalanine (phe), possible mental retardation, diet should be low in phe
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tay-sachs disease
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lacking hexosaminidase, symptoms- lose motor function, become deaf blind or mentally retarded
death usually occurs in early childhood most common among children of eastern european jewish descent |
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Autosomal dominant disorders
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dominant allele expressesed even in heterozygotes
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offspring of a heterozygous parent and normal homozygous recessive parents
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50% likely to be heterozygous
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severity of autosomal dominant disorders varies with the
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condition
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disorders due to dominant genes
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huntingtons disease, marfan syndrome, achondroplasia, familial hypercholesterolemia
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huntingtons disease
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symptoms appear after age 30:fatal
mutation on chromosome 4 |
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marfan syndrome
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defective form of protein fibrilin
symptoms include weakening of the wall of the aorta about 1 in 5000 humans have marfan syndrome |
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achondroplasia
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cartilage of limb bones doesnt develop properly
short stature |
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familial hypercholesterolemia
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leads to elevated blood levels and cholesterol
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genes on the x chromosome also are inherrited according to..?
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predictable patterns
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who are affected more?
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many more males than females
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why are females less affected?
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a recessive x allele can be masked in females
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who do daughters receive the affected allele from?
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an affected father
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disorders that are recessive x linked traits
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hemophilia,duchenne muscular dystrophy (DMD), red/green color blindness
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hemophilia
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two types: hemophilia A and hemophilia B
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hemophilia A
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most common form
mutation in the gene for clotting protein factor VIII |
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hemophilia B
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mutation in the gene for clotting protein factor IX
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why did queen victorias family have a higher frequency of hemophilia?
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due to marriage between close relatives
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duchenne muscular dystrophy (DMD)
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mutation in gene that encodes the protein dystrophin
weak muscles:break down of muscles death usually begins at age 20 due to cardiac repspitory failure |
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red/green color blindess
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mutation in the gene tat encodes for the protein opsin
genes for opsin and blood clotting factor VIII are closely linked |
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Rare X-linked abnomalities
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faulty enamel trait, testicular feminizing syndrome
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faulty enamel trait
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dominant x-linked allele
improper development of tooth enamel |
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testicular feminizing sydrome
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XY individual develops as a female externally
mutation on the X chromosome produces defective receptors for male hormones |
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what are factors that complicate genetic analysis?
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genetic analysis is a difficult task
may be necessary to combine pedigrees of similar families research will yield more information about genetic disorders |
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pharmacognetics
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identify genes that control common reactions to various drugs
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what would an idividual need?
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a genetic profile
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what could the physician select?
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the best drugs for that individual illness, improve patient care
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gene mutation
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change in one or more of the nucleotides that make up a gene
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various changes in chromosomes that could cause genetic disorders
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deletion, duplications, translocation, inversion
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what does deletion of part of a chromosome cause?
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spontaneous, viral, irradiation, chemical, or enviormental
permanent loss of genetic material |
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cri-du-chat
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one deletion of chromosome 5
abnormal mental development misshapen larynx |
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duplications
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gene sequences that are repeated
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translocations
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part of one chromosome exchanges places with corresponding part of a nonhomologous chromosome
rare cancers including leukemia |
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philidelphia chromosome
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extra-long chromosome 9 due to a piece of chromosome 22
(9/22 translocation) |
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inversion
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a segment of a chromosome is inverted 180 degrees
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aneuploidy
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embryo does have have an exact multiple of 23 chromosomes
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polyploidy
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embryo has three four or more set of 23 chromosomes (3n, 4n)
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when can chromosome numbers change?
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during mitosis, meiosis, or fertilization
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what is a common cause of abnormal numbers or autosomes?
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nondisjunction
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nondisjunction
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one or more pairs of chromosomes fails to seperate during cell division
increases with a womans age if such a gamete is fertalized: trisomy-3 of a certain chromosome monosomy- one |
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down syndrom, trisomy 21
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metal retardation, abnormal skeletal development, motor functions delayed, and weaker muscles
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what can nondisjunction also change?
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number of sex chromosomes
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turner syndrome (X)
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missing an x chromosome: XO
female: webbed neck, no secondary sexual traits at puberty, sterile, may age prematurely |
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poly-X female (XXX, XXXX)
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XXX develop normally (tend to be tall and thin)
XXXX severely mentally challenged |
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klinefelter syndrome (XXY)
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low fertility, metal retardation, small testes, sparse body hair, enlarged breasts
testosterone injections may reverse phentype |
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jacobs syndrome (XYY)
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taller
normal male phenotype severe acne speech and reading problems |
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non-disjuction that can lead to change in number of sex chromosomes
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turner syndrome (X), poly-X female (XXX, XXXX), klinefelter syndrome (XXY), jacobs syndrome (XYY)
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genetic disorders can result from?
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nondisjunction of x chromosomes
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