PCOL 838 Genetic Disease Terms
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Acrocentric - correct answer. Refers to the terminal location of the centromere on
chromosomes 13, 14, 15, 21, and 22.
Allelic heterogeneity - correct answer. The situation in which multiple alleles at a
single locus can produce one or more disease phenotypes.
Amorphic - correct answer. Refers to pathogenic variants that cause a complete loss
of function for the respective gene and therefore yield the same phenotype as a
complete gene deletion.
Aneuploidy - correct answer. A general term used to denote any unbalanced
chromosome complement.
Antimorphic - correct answer. Refers to pathogenic variants that, when present in
heterozygous form opposite a nonmutant allele, will result in a phenotype similar to
homozygosity for loss-of-function alleles.
Ascertainment bias - correct answer. The situation in which individuals or families in a
genetic study are not representative of the general population because of the way in
which they are identified.
Autosomal - correct answer. Located on chromosomes 1-22 rather than X or Y.
CpG island - correct answer. A segment of DNA that contains a relatively high density
of 5′-CG-3′ dinucleotides. Such segments are frequently unmethylated and located
close to ubiquitously expressed genes.
Dictyotene - correct answer. The end of prophase during female meiosis I in which
fetal oocytes are arrested prior to ovulation.
, Dominant - correct answer. A pattern of inheritance or mechanism of gene action in
which the effects of a variant allele can be observed in the presence of a nonmutant
allele.
Dominant negative - correct answer. A type of pathophysiologic mechanism that
occurs when a mutant allele interferes with the normal function of the nonmutant gene
product.
Dosage compensation - correct answer. Mechanism by which a difference in gene
dosage between two cells is equalized. For XX cells in mammals, decreased expression
from one of the two X chromosomes results in a concentration of gene product similar to
an XY cell.
End-product deficiency - correct answer. A pathologic mechanism in which absence
or reduction in the product of a particular enzymatic reaction leads to disease.
Epigenetic - correct answer. Refers to a phenotypic effect that is heritable, through
somatic cell division and/or across organismal generations, but that does not depend on
variation in DNA sequence. Instead, epigenetic inheritance is associated with alterations
in chromatin structure such as DNA methylation or histone modification that can be
transmitted during cell division.
Expressivity - correct answer. The extent to which a variant genotype affects
phenotype, including the tissues that are affected, and the severity of those effects.
Fitness - correct answer. The effect of a variant allele on an individual's ability to
produce offspring.
Founder effect - correct answer. One of several possible explanations for an
unexpectedly high frequency of a deleterious gene in a population. If the population was
founded by a small ancestral group, it may have, by chance, contained a large number
of carriers for the deleterious gene.
Gamete - correct answer. The egg or sperm cell that represents a potential
reproductive contribution to the next generation. Gametes have undergone meiosis and
so contain half the normal number of chromosomes found in zygotic cells.
Gene dosage - correct answer. The principle that the amount of product expressed for
a particular gene is proportionate to the number of gene copies present per cell.
Genetic anticipation - correct answer. A clinical phenomenon in which the phenotype
observed in individuals carrying a deleterious gene appears more severe in successive
generations. Possible explanations include ascertainment bias or a multistep mutational
mechanism such as expansion of triplet repeats.
Questions And Answers 100% Guaranteed
Success.
Acrocentric - correct answer. Refers to the terminal location of the centromere on
chromosomes 13, 14, 15, 21, and 22.
Allelic heterogeneity - correct answer. The situation in which multiple alleles at a
single locus can produce one or more disease phenotypes.
Amorphic - correct answer. Refers to pathogenic variants that cause a complete loss
of function for the respective gene and therefore yield the same phenotype as a
complete gene deletion.
Aneuploidy - correct answer. A general term used to denote any unbalanced
chromosome complement.
Antimorphic - correct answer. Refers to pathogenic variants that, when present in
heterozygous form opposite a nonmutant allele, will result in a phenotype similar to
homozygosity for loss-of-function alleles.
Ascertainment bias - correct answer. The situation in which individuals or families in a
genetic study are not representative of the general population because of the way in
which they are identified.
Autosomal - correct answer. Located on chromosomes 1-22 rather than X or Y.
CpG island - correct answer. A segment of DNA that contains a relatively high density
of 5′-CG-3′ dinucleotides. Such segments are frequently unmethylated and located
close to ubiquitously expressed genes.
Dictyotene - correct answer. The end of prophase during female meiosis I in which
fetal oocytes are arrested prior to ovulation.
, Dominant - correct answer. A pattern of inheritance or mechanism of gene action in
which the effects of a variant allele can be observed in the presence of a nonmutant
allele.
Dominant negative - correct answer. A type of pathophysiologic mechanism that
occurs when a mutant allele interferes with the normal function of the nonmutant gene
product.
Dosage compensation - correct answer. Mechanism by which a difference in gene
dosage between two cells is equalized. For XX cells in mammals, decreased expression
from one of the two X chromosomes results in a concentration of gene product similar to
an XY cell.
End-product deficiency - correct answer. A pathologic mechanism in which absence
or reduction in the product of a particular enzymatic reaction leads to disease.
Epigenetic - correct answer. Refers to a phenotypic effect that is heritable, through
somatic cell division and/or across organismal generations, but that does not depend on
variation in DNA sequence. Instead, epigenetic inheritance is associated with alterations
in chromatin structure such as DNA methylation or histone modification that can be
transmitted during cell division.
Expressivity - correct answer. The extent to which a variant genotype affects
phenotype, including the tissues that are affected, and the severity of those effects.
Fitness - correct answer. The effect of a variant allele on an individual's ability to
produce offspring.
Founder effect - correct answer. One of several possible explanations for an
unexpectedly high frequency of a deleterious gene in a population. If the population was
founded by a small ancestral group, it may have, by chance, contained a large number
of carriers for the deleterious gene.
Gamete - correct answer. The egg or sperm cell that represents a potential
reproductive contribution to the next generation. Gametes have undergone meiosis and
so contain half the normal number of chromosomes found in zygotic cells.
Gene dosage - correct answer. The principle that the amount of product expressed for
a particular gene is proportionate to the number of gene copies present per cell.
Genetic anticipation - correct answer. A clinical phenomenon in which the phenotype
observed in individuals carrying a deleterious gene appears more severe in successive
generations. Possible explanations include ascertainment bias or a multistep mutational
mechanism such as expansion of triplet repeats.
