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26 Cards in this Set
- Front
- Back
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What is euploid and aneuploid? What are some fun aneuploid prevalence facts?
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Euploid: chromosome number that is a multiple of the haploid number (23)
Aneuploid: not a multiple of 23. -accounts for 3-4% of clinically recognized pregnancies -~50% of 1st tri miscarriage |
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What is FISH
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flourescence in situ hybridization-it is a molecular cytogenetic trechnique that labels probes that identify chromosomes, parts of chromosomes or deletions.
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What is chromosomal microarray? Does it detect balanced rearrangements?
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Analyzes hundreds to thousands of genes and gives a computer generated profile of gene expression. Does NOT detect balanced rearrangements.
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What percentage of miscarriages does aneuploidy account for? Turner syndrome?
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about 50%
turner syndrome-20% (monosomy 45,X) |
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What is the gene rearrangement in down syndrome? What is the frequency? Is there a maternal age effect?
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There is a trisomy on the 21 chromosome.
Freq: 1/800 Risk increases with maternal age |
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What is used to determine the number of copies of a specific segment of DNA?
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FISH
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What is used to detect chromosomal imbalance?
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chromosomal microarray
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What is a reciprocal translocation? How many chromosomes in karyotype
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non homologous chromosomes break and are rearranged. Nothing is rearranged. 46 chromosomes in karyotype
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What is a robersonian translocation? How many chromosomes in karyotype
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fusion of 2 acrocentric chromosomes with loss of p arms. karyotype 45 chromosomes
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What is paracentric inversion? Is it lethal?
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paracentric means inverted segment does NOT contain the centromere lethal
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What is a pericentric inversion? Is it lethal?
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Inverted segment includes a centromere. potentially viable.
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What is the inheritance pattern of turner syndrome? What is the incidence in female births? accounts for what percentage of miscarriages?
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x-linked. 1/4000 female births, 20% of miscarriages.
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What is anticipation?
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The progressively earlier appearance and or increasing severity of the disease phenotype in successive generations
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What is the penetrance of fragile X syndrome in men and women?
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80% in men, 30% in women
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What percentage of mental retardation does fragile X syndrome account for in total and out of x-linked MR
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2-4% of all in total and 40% of all x linked.
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What is the Sherman paradox
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there is unequal inheritance in fragile x syndrome. there is unequal penetrance in males who inherit the disease.
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What gene is effected in fragile x and how? What does that mean for the cell?
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the FMR1 gene is effeced. There are CGG repeats that only happen in female transmission. The repeats are methylated which represses the promoter and there is no mRNA translation.
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What is genetic imprinting?
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modification of the expression of a gene or chromosome segment that depends on the parental origin that chromosomal segment
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Describe the transmission and expression of imprinted chromosomes
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transmission-medelian but expression determined by the gender of transmitting parent. chromosome 11 &15 have the most imprinted genes
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What does epigenic mean? What are some epigenic modifiers?
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Epigenic- change the degree of expression that affects the phenotype but not the genotype. Modifyers include: methylation, phosphorylation, acetlyation, post translational modifiers.
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How does monoallelic expression happen?
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One parent's allele has been methylated and is not able to be expressed and therefore the other parent's allele is the sole allele being expressed
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Do imprinted genes make it into the next generation.
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No it starts over again.
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What are some commonalities in methylation patterns?
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they are the same in different individuals in the same gender.
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What are some features of Prader-Willi Syndrome
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hypotonia and poor feeding in infancy. mild to moderate MR, undescended testes, short stature, obesity in later childhood eventually INDISCRIMINANT EATING HABITS
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Features of Angleman's syndrome
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more severe MR, seizures, no speech, hand flapping, ataxic gain, inappropriate laughter.
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What is uniparental disomy UDP? Heterodisomy? Isodisomy?
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Two copies of a given chromosome are derived from one parent.
heterodisomy-error in meiosis 2 (two copies of one homolog) isodisomy-error in meiosis 1 (two different homologs from one parent) |
