Pathophysiology of Disease exam questions and answers fully solved
- AnswersRefers to the terminal location of the centromere on chromosomes 13, 14, 15,
21, and 22.
Allelic heterogeneitc - AnswersThe situation in which multiple alleles at a single locus
can produce one or more disease phenotypes.
Amorphic - AnswersRefers to pathogenic variants that cause a complete loss of function
for the respective gene and therefore yield the same phenotypeas a complete gene deletion.
Aneuploidy - AnswersA general term used to denote any unbalanced chromosome
complement.
Antimorphic - AnswersRefers 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 - AnswersThe 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 - AnswersLocated on chromosomes 1-22 rather than X or Y.
CpG island - AnswersA segment of DNA that contains a relatively high density of 5 ′CG3 ′
dinucleotides. Such segments are frequently unmethylated and located close to ubiquitously
expressed genes.
Dictyotene - AnswersThe end of prophase during female meiosis I in which fetal oocytes
are arrested prior to ovulation.
Dominant - AnswersA 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 - AnswersA type of pathophysiologic mechanism that occurs when a
mutant allele interferes with the normal function of the nonmutant gene product.
Dosage compensation - Answersmechanism 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.
Endproduct deficiency - AnswersA pathologic mechanism in which absence or reduction
in the product of a particular enzymatic reaction leads to disease.
Epigenetic - AnswersRefers 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 - AnswersThe extent to which a variant genotype affects phenotype,
including the tissues that are affected, and the severity of those effects.
Fitness - AnswersThe effect of a variant allele on an individual's ability to produce
offspring.
Founder effect - AnswersOne 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 - AnswersThe 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 - AnswersThe principle that the amount of product expressed for a
particular gene is proportionate to the number of gene copies present per cell.
Genetic anticipation - AnswersA 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.
Haplotype - AnswersA set of closely linked DNA sequence variants on a single
chromosome.
Hemizygous - AnswersA term referring to the presence of only one allele at a locus,
either because the other allele is deleted or because it is normally not present; eg, Xlinked
genes in males.
Heterochromatin - AnswersOne of two alternative forms of chromosomal material (the
other is euchromatin) in which chromosomal DNA is highly condensed and, usually, devoid of
genes that are actively transcribed.
Heteroplasmy - AnswersThe mixture of abnormal and normal mitochondrial DNA
molecules in a single cell.
Heterozygote advantage - AnswersOne way to explain an unexpectedly high frequency
of a recessively inherited pathogenic variant in a particular population. During recent evolution,
carriers (ie, heterozygotes) are postulated to have had a higher fitness than homozygous
wildtype individuals.
- AnswersRefers to the terminal location of the centromere on chromosomes 13, 14, 15,
21, and 22.
Allelic heterogeneitc - AnswersThe situation in which multiple alleles at a single locus
can produce one or more disease phenotypes.
Amorphic - AnswersRefers to pathogenic variants that cause a complete loss of function
for the respective gene and therefore yield the same phenotypeas a complete gene deletion.
Aneuploidy - AnswersA general term used to denote any unbalanced chromosome
complement.
Antimorphic - AnswersRefers 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 - AnswersThe 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 - AnswersLocated on chromosomes 1-22 rather than X or Y.
CpG island - AnswersA segment of DNA that contains a relatively high density of 5 ′CG3 ′
dinucleotides. Such segments are frequently unmethylated and located close to ubiquitously
expressed genes.
Dictyotene - AnswersThe end of prophase during female meiosis I in which fetal oocytes
are arrested prior to ovulation.
Dominant - AnswersA 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 - AnswersA type of pathophysiologic mechanism that occurs when a
mutant allele interferes with the normal function of the nonmutant gene product.
Dosage compensation - Answersmechanism 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.
Endproduct deficiency - AnswersA pathologic mechanism in which absence or reduction
in the product of a particular enzymatic reaction leads to disease.
Epigenetic - AnswersRefers 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 - AnswersThe extent to which a variant genotype affects phenotype,
including the tissues that are affected, and the severity of those effects.
Fitness - AnswersThe effect of a variant allele on an individual's ability to produce
offspring.
Founder effect - AnswersOne 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 - AnswersThe 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 - AnswersThe principle that the amount of product expressed for a
particular gene is proportionate to the number of gene copies present per cell.
Genetic anticipation - AnswersA 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.
Haplotype - AnswersA set of closely linked DNA sequence variants on a single
chromosome.
Hemizygous - AnswersA term referring to the presence of only one allele at a locus,
either because the other allele is deleted or because it is normally not present; eg, Xlinked
genes in males.
Heterochromatin - AnswersOne of two alternative forms of chromosomal material (the
other is euchromatin) in which chromosomal DNA is highly condensed and, usually, devoid of
genes that are actively transcribed.
Heteroplasmy - AnswersThe mixture of abnormal and normal mitochondrial DNA
molecules in a single cell.
Heterozygote advantage - AnswersOne way to explain an unexpectedly high frequency
of a recessively inherited pathogenic variant in a particular population. During recent evolution,
carriers (ie, heterozygotes) are postulated to have had a higher fitness than homozygous
wildtype individuals.
