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MMSC 491 EXAM 2 QUESTIONS AND ANSWERS
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MMSC 491 EXAM 2 QUESTIONS AND ANSWERS
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MMSC 491 EXAM 2 QUESTIONS AND ANSWERSThe term phenotype can be applied to a wide range of manifestations. Which of the following properties, if any, do not constitute a phenotypic manifestation?
a. The number of digits a person has.
b. The transcriptome of a single T cell.
c. The sequence of a persons beta globin gene.
d. autistic behavior - Answer- c. The sequence of a persons beta globin gene.
Which, if any, of the following is incorrect? When used in human genetics,
a. the terms dominant and recessive apply equally to alleles and phenotypes.
b. dominant describes a phenotype that is manifested in the heterozygote, that is, the phenotype is attributable to just a single allele.
c. recessive describes a phenotype that is manifest as a result of the combined effects of both alleles at a locus.
d. the AB blood group is an example of a co-dominant phenotype. - Answer- a. the terms dominant and recessive apply equally to alleles and phenotypes.
With respect to autosomal recessive inheritance, which, if any, of the following statements is incorrect?
a. Affected individuals normally have unaffected parents.
b. For unaffected parents who have a previously affected child, there is a 1 in 4 risk of having an affected child on each occasion that they produce a new child.
c. Heterozygotes are always asymptomatic carriers.
d. Some affected individuals have alleles with identical pathogenic mutations but many have two different mutant alleles - Answer- c. Heterozygotes are always asymptomatic carriers.
With respect to X-chromosome inactivation in females, which, if any, of the following statements is incorrect?
a. X-inactivation first occurs in the preimplantation female mammalian embryo.
b. One of the two X chromosomes in each diploid cell of a normal woman is randomly selected to undergo X-inactivation and becomes highly condensed.
c. The process involves epigenetic silencing of each gene on one of the two X chromosomes, either the maternal X chromosome or the paternal X chromosome.
d. Once - Answer- c. The process involves epigenetic silencing of each gene on one of the two X chromosomes, either the maternal X chromosome or the paternal X chromosome.
With respect to X-linked recessive inheritance, which, if any, of the following statements is false? a. Males with just one mutant allele are affected because, lacking a second X chromosome, they do not have a normal allele.
b. Women are always asymptomatic.
c. The disorder is not transmitted from fathers to sons.
d. Each child born to a normal man and a carrier woman has a risk of 1in 4 of being affected. - Answer- b. Women are always asymptomatic.
With respect to X-linked dominant inheritance, which, if any, of the following statements is false?
a. There are significantly more affected females than males.
b. Each child born to an affected mother has a risk of 1 in 2 of being affected.
c. Each daughter born to an affected father has a risk of 1 in 2 of being affected.
d. Each boy born to an affected father has a negligible risk of being affected. - Answer- c. Each daughter born to an affected father has a risk of 1 in 2 of being affected.
With respect to mitochondrial inheritance, which, if any, of the following statements is false?
a. Affected individuals can be of either sex.
b. Mitochondrial disorders are transmitted virtually exclusively through the maternal line.
c. Both the sperm and the egg contribute mitochondrial DNA to the zygote, however, the
paternal mtDNA is destroyed in the early embryo.
d. Clinical variability is a common feature of mitochondrial DNA disorders.
e. All of the statements are true - Answer- e. All of the statements are true
With respect to mosaicism, which, if any, of the following statements, is false?
a. Any person who has two or more cells that have a different genetic constitution is a mosaic
b. All women are genetic mosaics
c. Every person is a genetic mosaic.
d. Mosaicism is the inevitable consequence of germline mutations. - Answer- d. Mosaicism is the inevitable consequence of germline mutations.
Purifying selection results in which of the following?
a. Removes harmful alleles from the population
b. Amplifies genes which can compensate for the loss of function mutant allele
c. Increases the frequency of a fitness conferring gene in the population
d. The process by which DNA is purified to carry out genetic testing. - Answer- a. Removes harmful alleles from the population
With respect to how miRNAs work, which, if any, of the following statements, is false? a. An miRNA is initially composed of two RNA strands, a passenger strand that will be destroyed and a complementary RNA, the guide strand, that is required for it to work.
b. an active miRNA regulates target protein-coding genes by binding to complementary sequences in the mRNA
c. A single miRNA normally binds to transcripts from just one target gene
d. A single type of mRNA can be regulated by multiple diffe - Answer- c. A single miRNA normally binds to transcripts from just one target gene
Which, if any, of the following is not regularly an epigenetic phenomenon that depends on DNA methylation or chromatin modification?
a. X-chromosome inactivation.
b. A position effect in which a gene is silenced by an inversion where both breakpoints occur within a euchromatic environment. c. Establishment of heterochromatin at a centromere. d. Imprinting - Answer- b. A position effect in which a gene is silenced by an inversion where both breakpoints occur within a euchromatic environment.
With respect to histone modifications, which, if any, of the following statements, is true?
a. histone acetylation always means adding an acetyl group to the side chain of a lysine
residue.
b. in histone acetylation each lysine of the histone is acetylated.
c. in histone phosphorylation a phosphate group is transferred to the side chain of a serine .
d. in histone methylation it is the DNA that coils around a nucleosome that is methylated, not the histone itself. - Answer- a. histone acetylation always means adding
an acetyl group to the side chain of a lysine residue.
With respect to noncoding RNA (ncRNA) , which, if any, of the following statements, is false?
a. Many long noncoding RNAs work in epigenetic regulation of gene expression.
b. Most regulatory long ncRNAs work as trans-acting regulators.
c. HOTAIR RNA is produced by a gene in the HOXC homeobox gene cluster at 12q13 but can regulate multiple genes within the HOXD gene cluster on chromosome 2.
d. HOTAIR RNA works as a scaffold that binds specific protein regulators at its two ends. - Answer- b. Most regulatory long ncRNAs work as trans-acting regulators
With respect to epimutations, which, if any, of the following statements, is false, from a practical viewpoint?
a. The term epimutation means an unexpected change in chromatin conformation, causing a g ene to be expressed in an abnormal way that is not related to its base sequence.
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