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99 Cards in this Set
- Front
- Back
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What is Genotype ?
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The Actual gene sequence
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What is Phenotype?
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The expression of a gene that can be seen or observed
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What does constitutional mean?
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Born with the Mutation
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What is an Allele?
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Alternative forms f a gene in the population each person has two alleles for a particular gene
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What is Hemizygous?
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Refers to an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two one example is the x-linked genes in male who under usual circumstances on have one X c'some
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What is Heteromorphism?
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having a variation from the normal gene sequence/location
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What is a Isochromosome
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It is a Chromosome that has lost one of its arms and replaced it with and exact copy of the other arm. Sometime seen is some females with Turner Syndrom or in tumor cells
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What is Retrotransposition
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Genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA. The copy themselves by making a mRNA and then via reverse transcriptase make a cDNA that inserts somewhere else in the DNA
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What does Reverse Transcriptase do?
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It takes a mRNA or other RNA sequence and converts it to the DNA sequence also known as cDNA
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What is Haploisufficiency?
When does this occur? |
It occurs when a diploid organism only has one functional copy of a gene and the other is mutated but the WT copy is unable to produce enough of the gene product to produce the WT effect so that individual has the mutated phenotype this occurs in Autosomal Dominant Disorders
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What is Genomic Imprinting?
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a genetic phenomenon when only a certain gene either from the mother or father is expressed and the other one is silenced. occurs in a parent of origin specific manner. Does not follow classical mendelian genetics.
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What is Heteroploid?
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When a cell ha a chromosomal number that is not an even multiple of the haploid chromosome number for that species
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What is a Karyotype?
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It is a characteristic chromosome complement of a eukaryote specie.
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What are the steps to Karyotyping?
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Blood samples are coagulated and seperated. Then the cells are grown in a media and then colchecine is added to prevent spindle fomation and cells in the metaphase stage and stained and examined
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What us a Giemsa Staining?
Bands? |
trypsin staining creates light and dark bands. Dark bands are A-T rich so for high resolution cells stopped at prometaphase
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Why are Alu and L1 sequences important in chromosome analysis??
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Because these sequences are involved in retrotranspotion and sometime these sequences cause mutation especially via hereditary disease like BRCA1
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Describe the BRCA1 gene, Tumor suppressor or oncogene?
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Tumor Supressor that could be made into an oncogene
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What is aneuploidy
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Any other number except an exact multiple of the haploid (euploid) like monosomy and trisomy
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What are the three trisomies and their names?
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21-down syndrom
18- Edwards Syndrom 13- Pateu syndrome |
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When could a trisomy be generated?
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from nondisjunction during meosis I and II
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What is the most common chromosome disorder
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tri-21
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What are older mother at risk for? Why?
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trisomies 13-18-21 because their eggs which have been with them all their lives may not have proper chromosomal separation during fertilization and could cause some chromosome not to detach from each other.
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What are some characteristics of Down Syndrome?
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Hypotonia, brachycephaly, flat occiput, short neck, flat nasal bridge, low set ears, mouth open showing furrowed protruding tongue, short finger and simian crease, fifth finger clinodatyly and eyes have brushfield spots
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What are some organ defects associated with down syndrom?
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low IQ, congenital heart defects, tracheoesophageal fistula, duodenal atresia, 15 times more likely to develop leukemia 50% live past 50 premature senility
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Define some features associated with Edwards syndrome?
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most female, 1in 8000 hypertonia, short sternum, prominent occiput, heart defect, receding jaw, specific fist clenching, low set malformed ears, rocker bottom feet, nails hypoplastic severe mental retardation most die by 6 month
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What are the features associated with Patau Syndrome?
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1in25000, most die by 6 month 50%by 1 month. severe growth and mental retardation, cleft lip/palate, congenital hear defects
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What is the genetic difference b/w nondisjunction occurring during meiosis I vs II
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I-gametes contain both parental chromosome which failed to separate.
II- the gametes will contain two identical copies of the same chromosome or neither |
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What is Euploid?
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an exact multiple of the haploid:
Diploid 2N, Triploid 3N, Tetraploid 4N |
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What is heteroploid?
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Chromosome something other than normal
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What is triploidy? viable? caused by?
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Three set of Chromosome 69 XXX, XXY, XYY
Rarely liveborn growth retardation and dysmorphic Caused by sperm that is diploid or an egg that is diploid that did not shed the polar body |
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What is tetraploidy? Viable? Why does it occur?
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4 sets of chromosomes:92 xxxx,xxyy
Rarely liveborn have severe mental retardation and dysmorphic features caused by mitotic nondisjunction in the first zygotic division |
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What monosomy is the only viable one? what is it called?
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X chromosome called turners syndrom
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What is the downfall of karyotyping?
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it has difficulty detecting chromosomal changes less that 3Mb
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WHat does FISH stand for?
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Fluorescence in situ hybridization
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WHat is FISH used for?
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used to diagnose a variety of syndromes, trisomies, and sub microscopic rearrangements
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At what stage does the cell have to be to perform FISH?
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can be performed on dividing or uncultured cells at interphase
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What is the use of Satellite probes and telomere probes in Fish
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to determine the # of a particular chromosome telomere -detect short repeats on end
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what can whole chromosome paint probes identify?
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only during metaphase can detect small chromosome rearrangements
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What are cosmids or region specific probes used for
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they are locus specific, used to detect microdeletions syndromes, gene mapping etc... cells can be in meta or interphase
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What types of abnormal chromsomes can you have?
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Numerical Defects, structural defects(present at birth) balanced structural abnormality-(no loss or gain of genetic material)
Unbalanced- you can get loss or gain |
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List the Chromosomal structural abnormalities
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Inversion
Insertion Deletion Duplication Translocations Robertsonian Translocation Ring Chromosome Isochromosome |
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WHat occurs during a chromosomal deletion?
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part of the chromosome is removed as to have a lost of genes can have interstitial (2 breaks in chromosome) or Terminal (1 break in chromosome)
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What occurs during chromosomal insertion? how many type? what are they?
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refers to a DNA segment the is removed and inserted somewhere else on the DNA 2 types-
Direct-same orientation as it was before in the DNA Inverted- orientation of DNA is reversed to the of the original |
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What is chromosomal translocation? what are the two types
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exchange of chromosomal material between two or more non-homologous chromosomes- results in two dericatives each name for the centromere they originated from two types reciprocal and robertsonian
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What is the difference between Insertion and Translocation
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Insertion you have no exchange of information between non homologous chromatids and does not involve recombination
Translocation is the actual movement of a loci and is usually reciprocal involves non homologous and it is the result of a recombination event |
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What is Duplication?
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When an additional copy of a chromosome segment which results in partial trisomy. results from unequal crossing over. less harmful than deletions however the chromosome break does disrupt genes which can lead to some phenotypic abnormalities
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What is a ring chromosome?
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Formed when two ends of a chromosome break and join forming a ring like structure. rings are unstable and may be lost during cell division
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WHat is an Isochromosome
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When you lose one arm and duplicate the other arm. result in three copies with lost of genetic material. Formed from abnormal division of the centromere
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What is Inversion? What are the two types
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When a segment of a chromosome is cut in two places turns around and rejoins. Paracentric-breaks on same chromosome does not involve centromere. Pericentric- involves centromere break on short and long arm of chromosome. Changes c;some. pairing leads to loop formation which after recombination events can lead to chromosomally unbalanced gametes. Dublication partial trisomy or deletion partial monosomy
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What can result in the children of chromosomal rearrangement carriers? two types
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Unbalanced- mentally retarded
Balanced- carriers are phenotypically normal but are at risk for producing a child with an unbalanced chromosome complement |
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what things can lead to trisomies
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non-disjunction as in trisomy 21, Robertsonian trans., q21q21 translocation, mosaic down syndrome (somatic mosaicism), partial trisomy.
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What occurs during robertsonian translocation? Which chromosomes does this occur with?
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you get fusion of the centromere region of two acrocentric chromosomes with a loss of the shortarm. 13,14,15,21,22
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During Robertsonian Trans why is no phenotypic defect seen?
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because there are no genes on the short arm
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What can be produced from robertsonian translocation?
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14,21balanced/t21tri/14mono/t14tri/21monosomy
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Are carriers of robertsonian translocation normal? Are they at risk for miscarriages and abnormal children?
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Yes
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What is ssomatic Mosaicism?
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When some cells have a trisomy while others dont. Caused by nondisjunction after fertilization
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What is partial trisomy? rare?
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Rare onl on a part of the long are q of chromosome 21 is present in triplicate
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What is an autosomal deletion syndrome?WHat is an example?
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Associated with either large or small deletion on chromosome. Cri du Chat syndrom-infant sounds like meowing cat due to hypertelorism which is epicanthal folds on the nose and have retro gnathia caused by a deletion in 5p mentally retarded
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What is the syndrome called from the 5p deletion? Hint 1% of mental institution people
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Cri du chat
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How does cri du chat result? IS it a cytogenetically visible autosomal deletion?
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15 % from unbalanced product from balanced parent. yes
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how are microdeletions and autosomal deletions detected?
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fish or high resolution chromosome analysis
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What causes DiGeorge syndrome? What is the frequency? AD or AR? location? Phenotype?What is used to detect it?
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Caused by a 3000 bp deletion 30 genes.
1:2000-4000 live birth AD on 22q11 Cranio facial anomalies, mental retardation and heart defect have tetrology of Fallot 40% pulomonary atresia and 60% absent pulmonary valve. Fish |
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What cause Prader-Willi Syndrome? PHenotype?
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Deletion of 15q11-13 on paternal chromosome
baby eating problems hyperphagia and obesity hypotonia cognitive impairment small hands and feet short stature MENTAL RETARDATION dysmorphism 70% caused by deletion |
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What is Angelman Syndrome
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a neuro-genetic disorder characterized by intellectual and developmental delay, sleep disturbance, seizures, jerky movements especially hand-flapping, frequent laughter or smiling, and usually a happy demeanour. AS is a classic example of genetic imprinting in that it is usually caused by deletion or inactivation of genes on the maternally inherited chromosome 15q11-13.
Short Stature seizures happy puppet |
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What is genomic imprinting?
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Imprinting is whether maternal or paternal genes are silenced or expressed in the baby at the chromatin level. Modified by methylation of cysteine or histone substitution. reversible
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WHen does genomic imprinting occur?
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Before fertilization
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What is Uniparental Disomy?
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When a child gets two copis of a chromosome like 15 is PWS or AS and the other parents contribution is missing
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What is a Hydatidiform Mole?
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An abnormal pregnancy where the placenta has grape like mass and the chorionic villi have epithelium wchi proliferates and the stroma undergoes cistic cavitation (mole)
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What causes hydatidiform mole? what can it lead to?
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when a sperm or egg fertilize an egg or sperm with no chromosome and the the csome double. Leads to choriocarcinoma
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WHat types of Hydatidiform mole can you have
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COMPLETE AND PARTIAL
Complete-trophoblast hyperplasia and atretic fetus Partial have triploidy with extra chromosomefrom from dad. have some fetal development and abnormal placenta short lived. If from mom then fetus completly atretic and severely abnormal development of the placenta and aborted |
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What is a teratoma? caused by?
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benign tumors caused from a 46 xx cells containing only maternal chromosomes
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What is Lyonization?
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when the X-chromosome is radomly inactivated but different in each cell allows for mosaicism. BARR BODIES
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How is a Barr Body created?
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Made from the Xist gene which inactivates one of the Xs in females
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What are common sex chromosome abnormalities in males and females?
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Males- Kleinfelters syndrome 47 XXY(tall male) or XYY syndrome (tall male).
Females- Turner syndrom (45X-) 47 XXX |
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What are is Klinefelters Syndrome?
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XXY 1:1000
infertile Normal till puberty then small testest, gynecomastia, learning dificulties below normal |
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Where does the defect occur usually in 50% of the cases in Klinefelters?
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from paternal Meosis I and in from females also in MI
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WHat are some other variations of Klinefelters?
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48-xxxt,xxyy, 49 xxxxy, and 46 xy/47 xxy mosaicism and wide phenotypic variaility
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What is 47 xyy syndrome? phenotype?
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cause by paternal nondisjunction at MII.
1:1000 tall normal intelligence, fertility normal add, impulsice slightly lower IQ |
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Turner Syndrome?
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1:4000 45x,46x/ixq, 45x/46xx etc...
Short stature, webbed neck, gonadal dysgenesis, low posterior hairline, widely spaced nipples, normal intelligence, spacial deficiency and fine motor.lymphedema of the hands and feet. 99 % of fetuses abort spontaneously. |
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Can Turner Syndrome be identified at birth?
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Yes
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Can turners be ring chromosome?
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yes and have mental retardation
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What is 47 XXX syndrome?
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1:1000 female births above average height. Normal phenotype and fertile but children are at risk from abnormality. learning difficulties and result from maternal meiosis errors and can also be xxxx, xxxxxx with more serious complications
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How can XY females arise?
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1-deletion of adrogen receptors from x chromosome also known as testicular feminization
2-Deletion of the TDF(SRY) Testes determining factor from the P arm of y due to inappropriate recombination |
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Are XY females fertile?
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NO
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XX males how does this monstrosity occur?
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abnormal remobination b/w X and Y in the pseudoautosomal region in male meiosis. So you have short arm translocation of the X so they are phenotypic males
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mechanism for XX Males? what is it a defect in?
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Female pseudohermaphroditism- masculinized external genitalia of 46 XX caused by adrenal hyperplasia where instead of producing the normal 3 adrenal steroids 2 are shunted to be converted to androgen production. due to a 21-hydroxylase defect
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At what age should women be screened?
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35 and above or previous child with abnormalities like trisomy, if parents have balanced chromosomal rearrangement, previous child with NTD or risk of genetic disease or if triple screen came back positive
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What is the triple screen test for?
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serum Alpha fetal protein ( fetus leaks fetal glycoprotein due to NTD) HCG and unconjugated Estriol (UE3)
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When should a triple screen be done
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15-20 weeks
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What does high AFP indicate
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NTD or Down
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What should the levels be for down
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AFP and uE3 low and HCG up
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What should the levels be for trisomy 18
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ALl down AFP uE3 and HCG
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WHat should the levels be for NTD
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AFP up
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When should someone get a chromosome analysis
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when a neonate is born with defects, growth problems, still birth, fertility problems, family history of csome problem, neoplasia, advanced menstrual age
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WHat type of screening is used for cancer?
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Spectral Karyotyping (SKY) where csome gain or loss can be seen by painting each csome differenctly
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Does a loss of a cell checkpoint result in genomic instability?
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Yes
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Can FISH be used for cancer cell analysis?
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yes
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If p53 is mutated in cancer cells how fast is csome amplification ?
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1000 fold
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What are the two types of chromosomal amplifications?
WHat are they a sign of |
Intrachromosomal amp- homogeneously staining region and Extrachromosomal amp- double minute chromosome dmin. THe are tags used in fish to identify what is being applified and how much and used to determine if a cell/s are cancerous
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